The Design of Rolling Bearing Mountings

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The Design of Rolling Bearing Mountings

PrefaceThis publication presents design examples coveringvarious machines, vehicles and equipment having onething in common: rolling bearings.For this reason the brief texts concentrate on the rollingbearing aspects of the applications. The operationof the machine allows conclusions to be drawn aboutthe operating conditions which dictate the bearingtype and design, the size and arrangement, fits, lubricationand sealing.Important rolling bearing engineering terms are printedin italics. At the end of this publication they aresummarized and explained in a glossary of terms, somesupplemented by illustrations.FAG 2


ContentsExample TitleSHIPBUILDINGPageRudder shafts . . . . . . . . . . . . . . . . . . . . . . 7956-57 Spherical roller bearings as ruddershaft bearings . . . . . . . . . . . . . . . . . . . . . . . 8058-59 Spherical roller thrust bearings asrudder carriers . . . . . . . . . . . . . . . . . . . . . . 8160 Spade-type rudder . . . . . . . . . . . . . . . . . . . 82Ship shafts61-62 Ship shaft bearings and stern tubebearings . . . . . . . . . . . . . . . . . . . . . . . . . . . 8463-64 Ship shaft thrust blocks . . . . . . . . . . . . . . 86PAPER MACHINES . . . . . . . . . . . . . . . 8965 Refiners . . . . . . . . . . . . . . . . . . . . . . . . . . . 9066 Suction rolls . . . . . . . . . . . . . . . . . . . . . . . 9267 Central press rolls . . . . . . . . . . . . . . . . . . . 9368 Dryer rolls . . . . . . . . . . . . . . . . . . . . . . . . . 9469 Guide rolls . . . . . . . . . . . . . . . . . . . . . . . . 9670 Calender thermo rolls . . . . . . . . . . . . . . . . 9871 Anti-deflection rolls . . . . . . . . . . . . . . . . 10072 preader rolls . . . . . . . . . . . . . . . . . . . . . . 101LIFTING AND CONVEYINGEQUIPMENTAerial ropeways, rope sheaves73 Run wheel of a material ropeway . . . . . . 10274 Rope return sheaves of passengerropeway . . . . . . . . . . . . . . . . . . . . . . . . . . 10475 Rope sheave (underground mining) . . . . 10676 Rope sheave of a pulley block . . . . . . . . . 108Cranes, lift trucks77 Crane pillar mounting with a sphericalroller thrust bearing . . . . . . . . . . . . . . . . 11078 Crane pillar mounting with a sphericalroller thrust bearing and a sphericalroller bearing . . . . . . . . . . . . . . . . . . . . . . 11179 Roller track assembly . . . . . . . . . . . . . . . 11280 Crane run wheel . . . . . . . . . . . . . . . . . . . 11481 Crane hook . . . . . . . . . . . . . . . . . . . . . . . 11682 Mast guidance bearings of afork lift truck . . . . . . . . . . . . . . . . . . . . . 117Belt conveyors83 Head pulley of a belt conveyor . . . . . . . . 11884 Internal bearings for the tension/take-up pulley of a belt conveyor . . . . . . 12085 Rigid idlers . . . . . . . . . . . . . . . . . . . . . . . 12286 Idler garland . . . . . . . . . . . . . . . . . . . . . . 123Example TitlePageExcavators and bucket elevators87 Bucket wheel shaft of a bucket wheelexcavator . . . . . . . . . . . . . . . . . . . . . . . . . 12488 Bottom sprocket of a bucket chaindredger . . . . . . . . . . . . . . . . . . . . . . . . . . 12589 Drive unit of a finished-goods elevator . 126CONSTRUCTION MACHINERY90 Driving axle of a construction machine . 12791 Vibrating road roller . . . . . . . . . . . . . . . . 128RAW MATERIAL PROCESSINGCrushers and mills92 Double toggle jaw crusher . . . . . . . . . . . 13093 Hammer mill . . . . . . . . . . . . . . . . . . . . . 13194 Double-shaft hammer crusher . . . . . . . . 13295 Ball tube mill . . . . . . . . . . . . . . . . . . . . . 13496 Support roller of a rotary kiln . . . . . . . . . 136Vibrating machines . . . . . . . . . . . . . . . . 13897 Two-bearing screen with circle throw . . . 13998 Two-bearing screen with straight-linemotion . . . . . . . . . . . . . . . . . . . . . . . . . . 14099 Four-bearing screen . . . . . . . . . . . . . . . . 142100 Vibrator motor . . . . . . . . . . . . . . . . . . . . 143STEEL MILL AND ROLLING MILLEQUIPMENT101-103 Large-capacity converters . . . . . . . . . . . . 144104 Roll bearings of a non-reversing fourhighcold rolling stand for aluminium . . 146105 Work rolls for the finishing section of afour-high hot wide strip mill . . . . . . . . . 148106 Roll mountings of a two-high ingotslab stand or ingot billet stand . . . . . . . . 149107 Combined reduction and coggingwheel gear of a billet mill . . . . . . . . . . . . 150108 Work rolls of a section mill . . . . . . . . . . . 152109 Two-high rolls of a dressing stand forcopper and brass bands . . . . . . . . . . . . . . 154110 Straightening rolls of a rail straightener . 156AGRICULTURAL MACHINERY ·FOOD INDUSTRY111 Disk plough . . . . . . . . . . . . . . . . . . . . . . 158112 Plane sifter . . . . . . . . . . . . . . . . . . . . . . . 160FAG 4


ContentsExample Title . . . . . . . . . . . . . . . . . . . . . . . . . . . .PagePRINTING PRESSES113 Impression cylinders of a newspaperrotary printing press . . . . . . . . . . . . . . . . 162114 Blanket cylinder of a sheet-fed offsetpress . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164PUMPS115 Centrifugal pump . . . . . . . . . . . . . . . . . . 165116-117 Axial piston machines . . . . . . . . . . . . . . . 166VENTILATORS, COMPRESSORS,FANS118 Exhauster . . . . . . . . . . . . . . . . . . . . . . . . 169119 Hot gas fan . . . . . . . . . . . . . . . . . . . . . . . 170120 Fresh air blower . . . . . . . . . . . . . . . . . . . . 171PRECISION MECHANICS,OPTICS, ANTENNAS121 Optical telescope . . . . . . . . . . . . . . . . . . 172Radiotelescope . . . . . . . . . . . . . . . . . . . . 174122 Elevation axle . . . . . . . . . . . . . . . . . . . . . 175123 Azimuth axis (track roller and kingpin bearings) . . . . . . . . . . . . . . . . . . . . . . 176124 Data wheel . . . . . . . . . . . . . . . . . . . . . . . 177GLOSSARY . . . . . . . . . . . . . . . . . . . . . 1785 FAG


1 Traction motor for electric standard-gauge locomotivesOperating dataThree-phase current motor supplied by frequencyconverter.Nominal output 1,400 kW, maximum speed4,300 min –1 (maximum driving speed for transmissionswith standard gear ratios is 200 km/h). One-enddrive with herringbone gear pinion.Bearing selection, dimensioningCollective loads which cover representative load casesfor the motor torque, speeds, and percentages of timefor the operating conditions in question, are used todetermine bearing stressing.Load case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .M d n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .qN m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .min –1 %1 6,720 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1,056 22 2,240 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1,690 343 1,920 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2,324 184 3,200 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2,746 425 2,240 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4,225 6The collective load is the basis for determining theaverage speeds (2,387 min –1 ) and the average drivingspeed (111 km/h). For each of the load cases the toothload acting on the pinion and the reaction loads fromthe bearings have to be calculated both for forward andbackward motion (percentage times 50 % each).In addition to these forces, the bearings are subjectedto loads due to the rotor weight, the unbalanced magneticpull, unbalanced loads and rail shocks. Of theseloads only the rotor weight, G L , is known; therefore, itis multiplied by a supplementary factor f z = 1.5...2.5 –depending on the type of motor suspension. The bearingloads are determined from this estimated load. Forthe spring-suspended traction motor shown, a supplementaryfactor f z = 1.5 is used.The bearing loads from weight and drive allow the resultantbearing loading to be determined by vectoraddition. In this example only the critical transmission-endbearing will be discussed. The attainable lifeL hna1...5 is determined for every load case using the formulaL hna = a 1 · a 23 · L h [h], taking into account theoperating viscosity of the transmission oil at 120 °C,the rated viscosity 1 as well as the factors K 1 and K 2 .The basic a 23II factor is between 0.8 and 3. The cleanlinessfactor s is assumed to be 1. Then, L hna is obtainedusing the formula:L hna =100q 1 q + 2L hna1 L hna2q + 3L hna3+ ...When selecting the bearing it should be ensured thatthe nominal mileage is reached and that, due to thehigh speed, the drive-end bearing is not too large.With the bearings selected the theoretical mileage of2.5 million kilometers required by the customer can bereached.A cylindrical roller bearing FAG NU322E.TVP2.C5.F1serves as floating bearing at the drive end; an FAG566513 with an angle ring HJ318E.F1 serves as thelocating bearing.The cylindrical roller bearing FAG 566513 is anNJ318E.TVP2.P64.F1, but its inner ring is 6 mmwider. The resulting axial clearance of 6 mm is requiredin order to allow the herringbone gearing on thepinion to align freely.Suffixes:ETVP2C5F1P64reinforced designmoulded cage of glass fibre reinforcedpolyamide, rolling element ridingradial clearance larger than C4FAG manufacturing and inspectionspecification for cylindrical roller bearings intraction motors which considers, amongothers, the requirements according to DIN43283 "Cylindrical roller bearings forelectric traction".tolerance class P6, radial clearance C4Machining tolerancesDrive end: shaft r5; end cap to M6Opposite end: shaft n5; end cap to M6The bearings are fitted tightly on the shaft due to thehigh load, which is sometimes of the shock type. Thisreduces the danger of fretting corrosion, particularly atthe drive end.Bearing clearanceDue to the tight fits, the inner ring of the bearing isexpanded and the outer ring with the roller-and-cageFAG 6


assembly is contracted. Thus the radial clearance of thebearing is reduced after mounting. It is further reducedduring operation as the operating temperatureof the inner ring is higher than that of the outer ring.For this reason bearings with an increased radial clearance(C4...C5) are mounted.Lubrication, sealingThe drive-end bearing is lubricated, due to the highspeeds, with transmission oil ISO VG 320 with EPadditives. No sealing is required between pinion andbearing so that a shorter cantilever can be used, thusreducing the bearing loading. Flinger edges and oilcollecting grooves prevent the oil from escaping in thedirection of the coil.1: Traction motor for electric standard-gauge locomotive7 FAG


2 Traction motor for electric commuter trainsThe bearing at the opposite end is lubricated with alithium soap base grease of NLGI penetration class 3(FAG rolling bearing grease Arcanol L71V).The bearings should be relubricated after 400,000 kilometersor five years, respectively. Multiple labyrinthsprevent contaminants from penetrating into the bearings.Operating dataSelf-ventilated converter current motor, permanentpower 200 kW at a speed of 1,820 min –1 (drivingspeed 72 km/h), maximum speed 3,030 min –1 (maximumdriving speed 120 km/h), one-end drive withherringbone gear pinion.Bearing selection, dimensioningThe operating mode of commuter train motor vehiclesis characterized by the short distances between stops.The periodic operating conditions – starting, driving,braking – can be recorded on an operating graph representingthe motor torque versus the driving time.The cubic mean of the motor torque and an averagespeed, which is also determined from the operatinggraph, form the basis for the rolling bearing analysis.The mean torque is about 90 % of the torque at constantpower.The bearing loads are calculated as for traction motorsfor standard-gauge locomotives (example 1). They aremade up of the reaction loads resulting from the gearforce on the driving pinion and a theoretical radialload which takes into account the rotor weight, themagnetic pull, unbalanced loads and rail shocks. Thistheoretical radial load applied at the rotor centre ofgravity is calculated by multiplying the rotor weight bythe supplementary factor f z = 2. The value 2 takes intoaccount the relatively rigid motor suspension.An overhung pinion provides the drive. At the pinionend a cylindrical roller bearing FAG NU320E.M1.P64.F1is mounted as the floating bearing. At the commutatorend a deep groove ball bearing FAG 6318M.P64.J20Avery safely accommodates the thrust load resultingfrom the 7° helical gearing of the pinion, even at relativelyhigh speeds.FAG 8


Current insulationWhere converter current motors with an output ofmore than 100 kW are used, ripple voltages can becaused by magnetic asymmetries. As a result, an inducedcircuit is generated between rotor shaft and statorwhich can cause current passage damage in thebearing.To interrupt the flow of current, one bearing (in thiscase the deep groove ball bearing) is provided with currentinsulation.Current-insulated bearings feature an oxide ceramiccoating on the outer ring O.D.s and faces.Ventilation endDrive end2: Traction motor of an electric commuter train9 FAG


3 Three-phase current standard motorOperating dataBelt drive: Power 3 kW; rotor mass 8 kg; nominalspeed 2,800 min –1 ; size 100 L; totally enclosed fancooledaccording to DIN 42673, sheet 1 – design B3,type of protection IP44, insulation class F.Bearing selectionLow-noise bearings in a simple, maintenance-freearrangement should be provided. These requirementsare best met by deep groove ball bearings.In DIN 42673, the shaft-end diameter specified forsize 100 L is 28 mm. Consequently, a bore diameter of30 mm is required. In this case a bearing of series 62was selected for both bearing locations, i.e. an FAG6206.2ZR.C3.L207. They guide the rotor shaft bothat the drive side and at the ventilating side. The springat the drive side provides clearance-free adjustment ofthe bearings and accommodates opposing axial loadson the rotor shaft.By adjusting the deep groove ball bearings to zeroclearance the adverse influence of bearing clearance onnoise behaviour is eliminated.Bearing dimensioningThe calculation of the bearings for this motor differssomewhat from the usual approach. As not even themotor manufacturer knows the amount of load at theshaft end, the permissible radial loading is indicated inthe motor catalogues.To determine the radial load carrying capacity, thedrive-side deep groove ball bearing is calculated.The calculation is based on an attainable life L hna of20,000 h and a basic a 23II value of 1.5. In addition, therotor weight, the unilateral magnetic pull and theunbalanced load have to be taken into account. As theDrive endlatter two criteria are not known the rotor weight issimply multiplied by a supplementary factor off z = 1.5.With these values a permissible radial loading of 1 kNis calculated for the shaft-end middle.Since the operating load in most applications is lowerthan the admissible load, an attainable life L hna of morethan 20,000 hours is obtained. The life of electric motorbearings, therefore, is usually defined not by materialfatigue but by the grease service life.Suffixes.2ZRC3L207Bearing with two shieldsRadial clearance larger than PN (normal)Grease filling with Arcanol L207Machining tolerancesShaft to j5; end cap bore to H6.The bore tolerance H6 ensures the slide fit required forfree axial adjustment of both bearings.Lubrication, sealingThe .2ZR design with shields on both bearing sideshas been successful in small and medium-sized electricmotors. The grease filling in these bearings is sufficientfor their entire service life. Increased operating temperaturesmust be taken into consideration in the case inquestion due to the insulation class F provided. Forthis reason the FAG high-temperature grease ArcanolL207 is used. The shields prevent the grease from escapingand protect the bearings from contaminationfrom the motor. Gap type seals protect the shaft openingat the drive side against dust and moisture. The requirementson insulation type IP44 are, therefore,met.Ventilation end3: Three-phase current standard motorFAG 10


4 Electric motor for domestic appliancesOperating dataPower 30 W; speed 3,500 min –1 .Bearing selectionQuiet running is the prime requirement for domesticappliance motors. The noise level of a motor is influencedby bearing quality (form and running accuracy),bearing clearance and the finish of the shaft and endcap bore.Today, the quality of standard bearings already adequatelymeets the common noise requirements.Zero-clearance operation of the bearings is achieved bya spring washer lightly preloading the bearings in theaxial direction.The bearing seats on the shaft and in the end cap boresmust be well aligned. To allow the spring washer toadjust the bearings axially, the outer rings have slide fitsin the end caps.A deep groove ball bearing FAG 626.2ZR is providedon the collector side, and an FAG 609.2ZR.L91 onthe other side.Suffixes.2ZR Bearing with shields on both sides; they form agap-type sealL91 special grease filling (Arcanol L91)Bearing dimensioningThe shaft diameter is usually dictated by the machinedesign, and as a result the bearings are sufficiently dimensionedwith regard to fatigue life. Fatigue damagehardly ever occurs; the bearings reach the required lifeof between 500 and 2,000 hours.Machining tolerancesShaft to j5; end cap bore to H5The bore tolerance H5 provides the slide fit requiredto permit free axial alignment of both bearings.Sealing, lubricationGrease lubrication with lithium soap base grease of consistencynumber 2 with an especially high degree ofcleanliness. It is characterized by its low friction. Theoverall efficiency of this motor is considerably influencedby the frictional moment of the ball bearings.The bearings with shields (.2ZR design) are prelubricatedwith grease, i.e. regreasing is not required. Thegap-type seal formed by the shields offers adequateprotection against contamination under normal ambientconditions.4: Electric motor for domestic appliances11 FAG


5 Drum of a domestic washing machineOperating dataThe bearing loads are:Capacity 4.5 kg dry mass of laundry(weight G w = 44 N);Speeds: when washing 50 min –1when spinning after prewash cycle 800 min –1when dry spinning 1,000 min –1Bearing AF rA =F · l 2[N]aBearing selectionThe domestic washing machine is of the front loadingtype. The drum is overhung and pulley-driven.Bearing selection depends on the journal diameterwhich is determined by rigidity requirements, and alsoon the weight and unbalanced loads. Very simplifieddata is assumed for bearing load determination, onwhich the bearing dimensions are based, since loadsand speeds are variable.Domestic washing machines generally have several,partly automatic, washing cycles with or without spinning.During the actual washing cycle, i.e. a cyclewithout spinning, the drum bearings are only lightlyloaded by the weight resulting from drum and wetlaundry. This loading is unimportant for the bearingdimensioning and is thus neglected. The oppositeapplies to the spinning cycle: Since the laundry is unevenlydistributed around the drum circumference, anunbalanced load arises which, in turn, produces a largecentrifugal force. The bearing dimensioning is basedon this centrifugal force as well as on the weights of thedrum, G T , and the dry laundry, G w . The belt pull isgenerally neglected.The centrifugal force is calculated from:F Z = m · r · 2 [N]wherem = G U /g [N · s 2 /m]Unbalanced load [N]. 10...35 % of the drylaundry capacity is taken as unbalanced load.g Acceleration due to gravity = 9.81 m/s 2G UrRadius of action of unbalanced load [m]Drum radius = d T / 2 [m] Angular velocity = π · n / 30 [s –1 ]n Drum speed during spinning [min –1 ]The total force for determination of the bearing loadsthus is: F = F Z + G T + G W [N]This load is applied to the washing drum centre.Bearing dimensioningBearing BF rB =F · l 1[N]aThe bearings for domestic washing machines aredimensioned for an index of dynamic stressingf L = 0.85...1.0.These values correspond to a nominal life of300...500 hours of spinning.In the example shown a deep groove ball bearing FAG6306.2ZR.C3 was selected for the drum side and adeep groove ball bearing FAG 6305.2ZR.C3 for thepulley side.The bearings have an increased radial clearance C3 andare sealed by shields (.2ZR) at both sides.Machining tolerancesDue to the unbalanced load G U ,the inner rings aresubjected to point load, the outer rings to circumferentialload. For this reason, the outer rings must have atight fit in the housing; this is achieved by machiningthe housing bores to M6. The fit of the inner rings isnot as tight; drum journal to h5. This ensures that thefloating bearing is able to adjust in the case of thermalexpansion. A loose fit also simplifies mounting.Lubrication, sealingThe bearings, sealed at both sides, are prelubricatedwith a special grease, sufficient for the bearing servicelife. There is an additional rubbing-type seal at thedrum side.FAG 12


PulleyDrum5: Drum mounting of a domestic washing machine13 FAG


6 Vertical-pump motorOperating dataRated horsepower 160 kW; nominal speed 3,000 min –1 ;Rotor and pump impeller mass 400 kg; pump thrust9 kN, directed downwards; type V1.Bearing selectionThe selection of the bearings is primarily based on themain thrust, which is directed downwards. It is madeup of the weight of the rotor and and pump impeller(4 kN), the pump thrust (9 kN) and the spring preload(1 kN). When the motor idles the pump thrust may bereversed so that the bearings have, briefly, to accommodatean upward axial load of 4 kN, as well.The radial loads acting on the bearings are not exactlyknown. They are made up by the unbalanced magneticpull and potential unbalanced loads from the rotorand pump impeller. However, field experience showsthat these loads are sufficiently taken into account bytaking 50 % of the rotor and pump impeller mass,which in this case is 2 kN.In the example shown, the supporting bearing is anangular contact ball bearing FAG 7316B.TVP whichhas to accommodate the main thrust. To ensure thatno radial force acts on the bearing this part of thehousing is radially relieved to clearance fit E8.In normal operation, the deep groove ball bearingFAG 6216.C3 takes up only a light radial load and theaxial spring preload; in addition, the thrust reversalload of the idling motor has to be accommodated.As a result, the rotor is vertically displaced in the upwarddirection (ascending distance) which is limitedby the defined gap between deep groove ball bearingface and end cap. To avoid slippage during the thrustreversal stage, the angular contact ball bearing is subjectedto a minimum axial load by means of springs.On the pump impeller side a cylindrical roller bearingFAG NU1020M1.C3 acts as the floating bearing. As itaccommodates the unbalanced loads from the pumpimpeller both the inner and the outer ring are fittedtightly.The cylindrical roller bearing design depends on theshaft diameter of 100 mm, which in turn is dictated bystrength requirements. Due to the relatively light radialload, the lighter series NU10 was selected.Machining tolerancesCylindrical roller bearing: Shaft to m5; housingto M6Deep groove ball bearing: Shaft to k5; housingto H6Angular contact ball bearing: Shaft to k5, housingto E8LubricationThe bearings are lubricated with FAG rolling bearinggrease Arcanol L71V and can be relubricated.Replenishment quantity– for the floating bearing 15 g– for the locating bearing 40 gThe relubrication interval is 1,000 hours. The spentgrease is collected in annular cover chambers providedbelow the bearing locations.FAG 14


6: Rotor bearing arrangement of a vertical-pump motor15 FAG


7 Mine fan motorOperating dataRated horsepower 1,800 kW; speed n = 750 min –1 ;Axial load F a = 130 kN; radial load F r = 3.5 kN;the bearings are vertically arranged.Bearing selectionThe axial load of 130 kN is made up of the weight ofthe rotor and the two variable top and bottom fan impellersas well as the thrust of these fan impellers. Theyare supported by the upper thrust bearing.The radial loads on vertical motors are only guidingloads. They are very small and generally result from theunbalanced magnetic pull and the potential rotor unbalancedload. In the example shown, the radial loadper bearing is 3.5 kN. If the exact values are notknown, these loads can be sufficiently taken intoaccount, assuming that half the rotor weight acts as theradial load at the rotor centre of gravity.The upper supporting bearing is a spherical rollerthrust bearing FAG 29260E.MB. Radial guidance isensured by a deep groove ball bearing FAG 16068Mmounted on the same sleeve as the supporting bearingand accommodating the opposing axial loads on therotor. Axial guidance is necessary for transporting andmounting as well as for motor idling. In this operatingcondition the counterflow of air can cause reversal ofrotation and thrust. The axial displacement is limitedto 1 mm in the upward direction so that the sphericalroller thrust bearing does not lift off. Springs arrangedbelow the housing washer (spring load 6 kN) ensurecontinuous contact in the bearings.Radial guidance at the lower bearing position is providedby a deep groove ball bearing FAG 6340M; it ismounted with a slide fit as the floating bearing. Sinceit is only lightly loaded, it is preloaded with springs of3 kN.Bearing dimensioningSpherical roller thrust bearing FAG 29260E.MB has adynamic load rating of C = 1430 kN. The index of dynamicstressing f L = 4.3 is calculated with the axial loadF a = 130 kN and the speed factor for roller bearingsf n = 0.393 (n = 750 min –1 ). The nominal lifeL h = 65,000 hours.Based on the operating viscosity of the lubricating oil(viscosity class ISO VG150) at approx. 70 °C, therated viscosity 1 and the factors K 1 und K 2 , a basic a 23IIvalue of about 3 is determined. The cleanliness factor sis assumed to be 1. The attainable life L hna of the thrustbearing is longer than 100,000 hours and the bearingis therefore sufficiently dimensioned. The two radialbearings are also sufficiently dimensioned with the indexof dynamic stressing f L > 6.Machining tolerancesUpper bearing locationSpherical roller thrust bearing: Shaft to k5; housingto E8Deep groove ball bearing: Shaft to k5; housingto H6Lower bearing locationDeep groove ball bearing:Lubrication, sealingShaft to k5; housingto H6Thrust and radial bearings at the upper bearing locationare oil-lubricated.The spherical roller thrust bearing runs in an oil bathand, due to its asymmetrical design, provides automaticcirculation from the inner to the outer diameter. Atapered oil feeder and angled oilways supply the upperbearing. A retaining and a flinger ring ensure oil supplyduring start-up.The lower bearing is grease-lubricated with provisionfor relubrication and a grease valve. Both bearing locationsare labyrinth-sealed.FAG 16


7: Rotor bearing arrangement of a mine fan motor17 FAG


8: Rotor shaft bearings of a wind energy plant19 FAG


9–18 Work spindles of machine toolsThe heart of every machine tool is its main or workspindle and its work spindle bearings. The main qualitycharacteristics of the spindle-bearing system arecutting volume and machining precision. Machinetools are exclusively fitted with rolling bearings of increasedprecision; mainly angular contact ball bearingsand spindle bearings (radial angular contact ball bearingswith contact angles of 15° and 25°, respectively),double-direction angular contact thrust ball bearings,radial and thrust cylindrical roller bearings and, occasionally,tapered roller bearings.Depending on the performance data required for amachine tool, the spindle bearing arrangement is designedwith ball or roller bearings based on the followingcriteria: rigidity, friction behaviour, precision,speed suitability, lubrication and sealing.This yields a viscosity ratio = / 1 ≈ 4; i. e. the rollingcontact areas are fully separated by a lubricant film.With = 4, a basic a 23II factor of 3.8 is obtained fromthe a 23 diagram. Since the bearings, as a rule, are relativelylightly loaded (f s* > 8), a very good cleanlinessfactor (s = infinite) is obtained with increased (V = 0.5)and utmost (V = 0.3) cleanliness. Consequently, thefactor a 23 (a 23 = a 23II · s), and thus the attainable life(L hna = a 1 · a 23 · L h ) becomes infinite; the bearing isfailsafe.So, as long as f s* ≥ 8 and the main spindle bearings arelubricated well ( ≥ 4), only the cleanliness in the lubricatinggap determines whether the bearing is failsafeor not.Out of a multitude of possible spindle bearing arrangementsfor machine tools a few typical arrangementshave proved to be particularly suitable for applicationin machine tools (figs. a, b, c).DimensioningUsually, a fatigue life calculation is not required for thework spindles since, as a rule, to achieve the requiredspindle and bearing rigidity, bearings with such a largebore diameter have to be selected that, with increasedor utmost cleanliness in the lubricating gap, the bearingsare failsafe. For example, the index of dynamicstressing f L of lathe spindles should be 3...4.5; this correspondsto a nominal life of L h = 15,000...50,000 h.Example: The main spindle bearing arrangement of aCNC lathe (fig. a) is supported at the work end inthree spindle bearings B7020E.T.P4S.UL in tandem-O-arrangement (contact angle 0 = 25°, C = 76.5 kN,C 0 = 76.5 kN). At the drive end, the belt pull is accommodatedby a double-row cylindrical roller bearingNN3018ASK.M.SP. The cutting forces cause 50 %each of the axial reaction forces for the two tandemarrangedspindle bearings. The front bearing at thework end accommodates 60 % of the radial forces. It isloaded with F r = 5 kN, F a = 4 kN at n = 3,000 min –1 .If the bearings are lubricated with the lithium soapbase grease FAG Arcanol L74V (base oil viscosity23 mm 2 /s at 40 °C), an operating viscosity of = 26 mm 2 /s will be obtained at an operating temperatureof 35 °C. With the mean bearing diameterd m = 125 mm and the speed n = 3,000 min –1 a ratedviscosity of 1 = 7 mm 2 /s is obtained.a: Spindle bearing arrangement with universal-design spindle bearings(spindle bearing set), subjected to combined load, at the workend and a single-row or double-row cylindrical roller bearing at thedrive end which accommodates only radial loads.b: Spindle bearing arrangement with two tapered roller bearings inO arrangement. The bearings accommodate both radial and axialloads.c: Spindle bearing arrangement with two double-row cylindricalroller bearings and a double-direction angular contact thrust ballbearing. Radial and axial loads are accommodated separately.FAG 20


9 Drilling and milling spindleOperating dataInput power 20 kW; range of speed 11...2,240 min –1 .Bearing selectionRadial and axial forces are accommodated separately.The radial bearings are double-row cylindrical rollerbearings – an FAG NN3024ASK.M.SP at the workend and an FAG NN3020ASK.M.SP at the oppositeend. The double-direction angular contact thrust ballbearing FAG 234424M.SP guides the spindle in axialdirection. This bearing has a defined preload andadjustment is, therefore, not required.Machining of the housing bore is simplified in that thenominal outside diameters of the radial and thrustbearings are the same. The O.D. tolerance of the angularcontact thrust ball bearing is such as to provide aloose fit in the housing.Lubrication, sealingCirculating oil lubrication.The labyrinth seal at the work end consists of ready-tomount,non-rubbing sealing elements. The inner labyrinthring retains the lubricating oil, the outer labyrinthring prevents the ingress of cutting fluid.Machining tolerancesBearing Seat Diameter Form tolerance Axial runout tolerancetolerance (DIN ISO 1101) of abutment shoulderCylindrical roller bearing Shaft, tapered Taper 1:12 IT1/2 IT1Housing K5 IT1/2 IT1Angular contact thrust bearing Shaft h5 IT1/2 IT1Housing K5 IT1/2 IT19: Drilling and milling spindle21 FAG


10 NC-lathe main spindleOperating dataInput power 27 kW;maximum spindle speed 9,000 min –1 .Main spindle bearings do not normally fail due to materialfatigue but as a result of wear; the grease servicelife is decisive.Bearing selectionThe main requirements on this bearing arrangementare an extremely good speed suitability, rigidity, andaccurate guidance of the work spindle. At the workend, a spindle bearing set FAG B7017C.T.P4S.DTLin tandem arrangement is provided; at the drive end, aspindle bearing set FAG B71917C.T.P4S.DTL intandem arrangement.The bearings are lightly preloaded (UL) and have anincreased precision (P4S).The arrangement has no floating bearing; it is a rigidlocating bearing system. Both bearing groups togetherform an O arrangement.Bearing clearanceFAG spindle bearings of universal design are intendedfor mounting in X, O or tandem arrangement in anyarrangement. When mounting in X or O arrangement adefined preload results. The light preload UL meetsthe normal requirements.The original preload remains in the bearings due toouter and inner spacer sleeves of identical lengths.With a good bearing distance, the axial and radial heatexpansions of the work spindle compensate each otherso that the bearing preload remains unchanged underany operating condition.Bearing dimensioningThe size of the bearings is primarily based on the spindlerigidity required, i. e. on the largest possible spindlediameter. The fatigue life of the bearings is takeninto account for dimensioning but it does not play adominating role in practice.Lubrication, sealingThe bearings are greased for life with the FAG rollingbearing grease Arcanol L74V and about 35 % of thecavity is filled.Sealing is provided by labyrinth seals with defined gaps.Machining tolerancesBearing Seat Diameter Form tolerance Axial run-out tolerance oftolerance (DIN ISO 1101) abutment shoulderSpindle bearings Shaft +5/–5 µm 1.5 µm 2.5 µmDrive end/work end Housing +2/+10 µm 3.5 µm 5 µm10: NC-lathe main spindleFAG 22


11 CNC-lathe main spindleOperating dataInput power 25 kW;Speed range 31.5...5,000 min –1 .Apart from the Hertzian contact pressure, the servicelife of the bearings is mainly dictated by the greaseservice life. Main spindle bearings do not normally faildue to material fatigue but as a result of wear.Bearing selectionThe bearings must accurately guide the spindle radiallyand axially and be very rigid. This is achieved by selectingas large a shaft diameter as possible and a suitablebearing arrangement. The bearings are preloaded andhave an increased precision.At the work end a spindle bearing set FAGB7018E.T.P4S.TBTL in tandem-O-arrangement witha light preload is mounted as locating bearing.At the drive end there is a single-row cylindrical rollerbearing FAG N1016K.M1.SP as floating bearing.This bearing arrangement is suitable for high speedsand for high cutting capacities.Bearing dimensioningThe bearing size is primarily based on the spindlerigidity required, i.e. on the spindle diameter. Thefatigue life of the bearings is taken into account fordimensioning but it does not play a dominating role inpractice.Bearing clearanceFAG spindle bearings of universal design are intendedfor mounting in X, O or tandem arrangement in anyarrangement. When mounting in X or O arrangement aset preload results. The light preload UL meets thenormal requirements.The cylindrical roller bearing is adjusted with almostzero radial clearance by axially pressing the taperedinner ring onto the spindle.Lubrication, sealingThe bearings are greased for life with the FAG rollingbearing grease Arcanol L74V.Approximately 35% of the spindle bearing cavity andapproximately 20% of the cylindrical -roller bearingcavity is filled with grease.Sealing is provided by a labyrinth with set narrowradial gaps.Machining tolerancesBearing Seat Diameter Form tolerance Axial runout tolerancetolerance (DIN ISO 1101) of abutment shoulderSpindle bearings Shaft +5/–5 µm 1.5 µm 2.,5 µmHousing –4/+8 µm 3.5 µm 5 µmCylindrical roller bearings Shaft, tapered Taper 1:12 1.5 µm 2.5 µmHousing –15/+3 µm 3.5 µm 5 µm11: CNC-lathe main spindle23 FAG


13 High-speed motor milling spindleOperating dataInput power 11 kW;maximum spindle speed 28,000 min –1 .Bearing selectionThe bearings must be suitable for very high speeds andfor the specific thermal operating conditions in a motorspindle. Hybrid spindle bearings with ceramic ballsare particularly suitable for this application.Milling spindles must be guided extremely accuratelyboth in the axial and in the radial direction.Work end:1 spindle bearing set FAG HC7008E.T.P4S.DTL intandem arrangement.Drive end:1 spindle bearing set FAG HC71908E.T.P4S.DTL intandem arrangement.The bearing pairs at drive end and work end aremounted in O arrangement and elastically adjusted bymeans of springs (spring load 300 N), correspondingto a medium preload. The bearing pair at the drive endis mounted on a sleeve which is supported on a linearball bearing with zero clearance so that axial lengthvariations of the shaft can be freely compensated for.Bearing dimensioningBearing size and bearing arrangement are selected onthe basis of the specified speed and on the spindlediameter.Two other factors that have to be taken into accountare the heat generated by the motor, which causes amajor temperature difference between the inner ringand the outer ring of the bearing, and the ring expansionwhich makes itself felt by the centrifugal force resultingfrom the high speed. In a rigid bearing arrangement,this would considerably increase the preload.Due to the spring preload, both these influences areeasily compensated for. As a result, the contact pressurein the rolling contact area of the bearing is relativelylow (p 0 ≤ 2,000 N/mm 2 ), and the bearings arefailsafe. Consequently, the service life of the bearings isdictated by the grease service life.Lubrication, sealingThe bearings are lubricated with rolling bearing greaseArcanol L207V which is particularly suitable for thegreater thermal stressing and for high speeds.To protect the grease from contamination, and consequentlyto increase the grease service life, the bearingsare sealed by labyrinths consisting of a gap-type sealwith flinger grooves and a collecting groove.Machining tolerancesBearing Seat Diameter Form tolerance Axial runout tolerancetolerance (DIN ISO 1101) of abutment shoulderSpindle bearing Shaft +6/+10 µm 1 µm 1.5 µm(drive/work end) Housing –3/+5 µm 2 µm 3 µm13: Bearing arrangement of a high-speed motor milling spindle25 FAG


14 Motor spindle of a latheOperating dataInput power 18 kW;maximum spindle speed 4,400 min –1 .obtained whose load carrying capacity is more thanadequate.Consequently, the service life of the bearings is primarilydictated by the grease service life.Bearing selectionThe bearings must be very rigid and accurately guidethe spindle in the radial and axial direction. This isachieved by selecting as large a shaft diameter as possibleand a suitable bearing arrangement. The bearingsare preloaded and have an increased precision. Also,the specific thermal conditions found in a motor bearingarrangement have to be taken into account.Work end: 1 spindle bearing setFAG B7024E.T.P4S.QBCL(tandem-O-tandem arrangement )as locating bearingOpposite end: 1 cylindrical roller bearingFAG N1020K.M1.SPas floating bearing.Bearing dimensioningAs the bearing size primarily depends on the spindlerigidity (larger spindle diameter) bearing sizes areBearing clearanceThe spindle bearings are mounted with a light preload.The cylindrical roller bearing is adjusted to a radialclearance of a few µm by axially pressing the taperedinner ring onto the tapered shaft seat and reaches therequired zero clearance at operating temperature.Lubrication, sealingThe bearings are lubricated for life with the rollingbearing grease Arcanol L207V. This grease is particularlysuitable for increased temperatures and high speeds.Approximately 35 % of the spindle bearing cavity andapproximately 20 % of the cylindrical-roller bearingcavity is filled with grease.Sealing is provided by a stepped labyrinth with collectinggrooves and drain holes. A gap-type seal protectsthe cylindrical roller bearing from external contamination.Machining tolerancesBearing Seat Diameter Form tolerance Axial runout tolerancetolerance (DIN ISO 1101) of abutment shoulderSpindle bearing Shaft –5/+5 µm 1.5 µm 2.5 µmHousing –4/+10 µm 3.5 µm 5 µmCylindrical roller bearing Shaft, tapered 1:12 1.5 µm 2.5 µmHousing –15/+3 µm 3.5 µm 5 µm14: Motor spindle bearing arrangement of a latheFAG 26


15 Vertical high-speed milling spindleOperating dataInput power 2.6/3.14 kW;Nominal speed 500...4,000 min –1 .Bearing selectionThe bearings must operate reliably over the entirespeed range from 500 to 4,000 min –1 . For example,the spindle must be rigidly guided at 500 min –1 underheavy loads both in the radial and axial direction. Onthe other hand, at the maximum speed of 4,000 min –1 ,the bearing temperature must not be so high as to impairaccuracy.At the milling spindle work end a spindle bearing setFAG B7014E.T.P4S.TBTM are mounted in tandem-O-arrangement with a medium preload. The bearinggroup is preloaded with 1.9 kN by means of a nut anda spacer sleeve.The deep groove ball bearing FAG 6211TB.P63guides the spindle at the drive end. To ensure clearance-freeoperation this bearing is lightly preloaded bymeans of Belleville spring washers.Drive endBearing dimensioningMilling spindles must be resistant to deflection andtorsion. This requirement dictates the spindle diameterand the bearing size. The required bearing rigidity isobtained by the chosen bearing arrangement and preload.The two angular contact ball bearings arranged atthe upper drive end accommodate the driving forces.Machining tolerancesSeat Diameter Cylindricity Axial runouttolerance tolerance tolerance of(DIN ISO 1101) abutment shoulderShaft js4 IT1/2 IT1Housing JS5 IT2/2 IT2(work end)Housing H6 IT3/2 IT3(drive end)Work endLubrication, sealingThe bearings are grease lubricated (FAG rolling bearinggrease Arcanol L74V).A gap-type seal with oil splash ring and collectinggrooves protect the spindle bearings from contamination.15: Bearing arrangement of a vertical high-speed milling spindle27 FAG


16 Bore grinding spindleOperating dataInput power 1.3 kW; spindle speed 16,000 min –1 .The spindle is radially loaded by the grinding pressure.The load depends on grinding wheel quality, feed anddepth of cut.Bearing selectionDue to the high speeds required during bore grinding,the spindle speeds must also be high. Sufficient rigidityand accurate guidance, especially in axial direction, arealso required. The demands for high speed and high rigiditycan be met with spindle bearings. As the spindlerequires primarily a high radial rigidity, it is advisableto provide bearings with a contact angle of 15° (designC).At the work end and at the drive end there is one spindlebearing set FAG B7206C.T.P4S.DTL in tandemarrangement each. The load is equally shared by theseO arranged tandem bearing pairs. For this purpose thespacer rings must be identical in width and also flushground.The bearings are lightly preloaded by a coil spring forclearance-free operation under all operating conditions.The preload increases the rigidity of the bearingarrangement. It is, however, limited by the permissiblebearing temperature and varies between 300 and500 N depending on the spindle application.The spindle diameter, which determines the bearingsize, is based on the required rigidity.Lubrication, sealingGrease lubrication for high-speed bearings (FAG rollingbearing grease Arcanol L74V). The bearings arelubricated for life during mounting and therefore norelubrication is required.The high-speed bearings require the use of non-rubbingseals, in this case labyrinth seals.Machining tolerancesSeat Diameter Cylindricity tolerance Axial runout tolerancetolerance (DIN ISO 1101) of abutment shoulderShaft js3 IT0/2 IT0Housing (drive end) +2/+6 µm IT1/2 IT1Housing (work end) –1/+3 µm IT1/2 IT1Drive endWork end16: Bearing arrangement of a bore grinding spindleFAG 28


17 External cylindrical grinding spindleOperating dataInput power 11 kW; speed n = 7,500 min –1 ; runningaccuracy: radially 3 µm, axially 1 µm.Bearing selectionDuring external cylindrical grinding a high cutting capacityis required (for rough grinding) and a high standardof form and surface quality (for fine grinding). Ahigh degree of rigidity and running accuracy as well asgood damping and speed suitability form the main criteriafor the bearing arrangement. These requirementsare met by precision bearings.Sealed universal spindle bearings with small steel balls(HSS) are used:– at the work end: 1 spindle bearing setFAG HSS7020C.T.P4S.QBCL in double-O arrangement as locating bearing– at the drive end: 1 spindle bearing setFAG HSS7020C.T.P4S.DBL in O arrangement asfloating bearingWhere even higher speeds have to be accommodated,it is advisable to use sealed hybrid spindle bearingsHCS with small ceramic balls (lower centrifugalforces).Bearing dimensioningThe required spindle diameter or the specified outsidediameter of the quill determines the bearing size. Thecontact angle of 15° is suitable for high radial rigidity.Damping and running accuracy are improved byarranging four bearings at the work end.Bearing clearanceAll UL universal design bearings are lightly preloadedwhen mounted in O arrangement. Spacers improve thethermal conditions and provide a larger spread at thebearing location. To ensure that the defined bearingpreload is not altered by the spacers, the latter must beidentical in width and flush ground.Lubrication, sealingThe sealed FAG HSS spindle bearings require nomaintenance and are lubricated for life with the FAGrolling bearing grease Arcanol L74.Additional sealing is provided at the grinding wheelend by a labyrinth with defined narrow axial gaps of0.3 ... 0.8 mm. A plain labyrinth seal is sufficient at thedrive end.Machining tolerancesBearing Seat Diameter Form tolerance Axial runout tolerancetolerance (DIN ISO 1101) of abutment shoulderSpindle bearing Shaft +3/–3 µm 1 µm 1.5 µm(work end) Housing -3/+5 µm 2 µm 3.5 µmSpindle bearing Shaft +3/–3 µm 1 µm 1.5 µm(drive end) Housing +5/+13 µm 2 µm 3.5 µm17: Bearing arrangement of an external cylindrical grinding spindle29 FAG


18 Surface grinding spindleOperating dataGrinding motor power 220 kW; maximum speed375 min –1 ; weight of spindle, rotor and grinding spindlehead 30 kN; maximum grinding pressure 10 kN.Bearing selectionThe spindle is supported at the grinding spindle headby a double-row cylindrical roller bearing FAGNN3060ASK.M.SP. The thrust ball bearing FAG51164MP.P5 arranged above this bearing absorbs thethrust component of the grinding pressure. The upperend of the spindle is fitted with a double-row cylindricalroller bearing FAG NN3044ASK.M.SP and athrust ball bearing FAG 51260M.P6. The cylindricalroller bearing provides radial guidance; the thrust ballbearing carries the weight of the rotor, spindle, andspindle head. To increase axial rigidity this bearing isadjusted with Belleville spring washers against thelower thrust ball bearing.Bearing dimensioningRigid spindle guidance in the radial direction is ensuredby accurately dimensioned mating parts, tightfits of the rings, and a light preload of the cylindricalroller bearings. The inner rings are pushed along thetapered bearing seat until the roller-and-cage assemblyruns under a light preload (5 µm). Surface finish anddimensional accuracy of the workpiece mainly dependon the axial rigidity of the spindle headstock and of therotary table. Therefore, the rigidity of the thrust bearingsis especially important. To increase the rigidity, thethrust bearings are preloaded to 40 kN by Bellevillespring washers at the upper end of the spindle. Sincethe combined weight of spindle, rotor, and spindlehead is 30 kN, the lower thrust bearing is preloaded to10 kN. Rigid, clearance-free spindle guidance also inthe axial direction is, therefore, guaranteed. The nominalrigidity is 2.5 kN/µm; the spindle deviates axiallyby only 4 µm with the maximum grinding pressure of10 kN.Lubrication, sealingThe headstock bearings are lubricated for life withFAG rolling bearing grease Arcanol L74V. A gap-typeseal suffices at the upper spindle end since the headstockis protected by a cap.A shaft seal prevents grease from penetrating into themotor. The lower bearings are sealed at the motor endwith a gap-type seal and at the spindle head with a gaptypeseal preceded by a labyrinth.18: Bearing arrangement of a surface grinding spindleFAG 30


19 Rotary table of a vertical latheOperating dataInput power 100 kW; speeds up to n = 200 min –1 ;rotary table O.D. 2,000, 2,200 or 2,500 mm; maximumworkpiece diameter 2,800 mm, maximum workpieceheight 2,700 mm, maximum workpiece weight250 kN; maximum radial and axial runout 5 µm.Bearing selectionThe face plate bearings must provide a high runningaccuracy and rigidity. As the thrust load predominatesand eccentric load application causes a great tiltingmoment, a thrust ball bearing of increased precision(main dimensions 1,250 x 1,495 x 150 mm) is installed.Radial guidance is provided by an angular contactball bearing of increased precision, FAG7092MP.P5 (30° contact angle). Both bearings are preloadedagainst each other with 50 kN.The high preload guarantees a high running accuracywhile ensuring a high radial and axial moment or tiltingrigidity and keeping internal heating relatively low.By taking special measures during mounting and afterfinal grinding of the rotary table a maximum axial runoutof 5 µm is obtained.Machining tolerancesThrust ball bearing: gearing to j5Angular contact ball bearing: kingpin to j5/gearing to K6Lubrication, sealingThe bearings have circulating oil lubrication.The oil is fed directly to the various bearings throughoil feed ducts. After flowing through the bearings, theoil passes through a filter and into an oil collectingcontainer from where it returns to the bearings.The labyrinth seal prevents the oil from escaping fromthe bearings and protects them from contamination.19: Bearing arrangement of a rotary table of a vertical lathe31 FAG


20 Tailstock spindleOperating dataMaximum speed n = 3,500 min –1Cylindrical roller bearings have a high radial loadcarrying capacity, and angular contact ball bearingswith a 40° contact angle have a high axial load carryingcapacity.Bearing selection, dimensioningThe bearing arrangement must be particularly rigidand have a high load carrying capacity. Other requirementssuch as precision and high-speed suitability aremet by bearings of precision design.At the work end the high radial load is accommodatedby a double-row cylindrical roller bearing FAGNN3014ASK.M.SP. The high axial load is accommodatedat the opposite end by four angular contact ballbearings FAG 7210B.TVP.P5.UL. Three of these bearingsare mounted in tandem arrangement; the fourthbearing is merely for axial counter guidance.The maximum bearing O.D. is dictated by the size ofthe quill.Bearing clearanceThe cylindrical roller bearing with a tapered bore ispreloaded with 2...3 µm by pressing the inner ring onto the tapered shaft seat (taper 1:12).The angular contact ball bearings of universal designUL have a light preload in the O arrangement. The twospacers are identical in width and exclusively serve toprovide a cavity which can accommodate the excessgrease escaping from the bearings.Lubrication, sealingThe bearings are lubricated for life with FAG rollingbearing grease Arcanol L135V. A labyrinth seal preventsdirt from penetrating into the bearings.Machining tolerancesBearing Seat Diameter Form tolerance Axial runout tolerancetolerance (DIN ISO 1101) of abutment shoulderShaft, tapered Taper 1:12 1.5 µm 2 µmCylindrical roller bearing Housing –13 / +2 µm 2.5 µm 4 µmShaft –4 / +4 µm 1.5 µm 2 µmAngular contact ball bearings Housing –4 / +6 µm 2.5 µm 4 µm20: Bearing arrangement of a tailstock spindleFAG 32


21 Rough-turning lathe for round bars and pipesRough-turning lathes are used for particularly economicalproduction of bars and pipes to tolerance classh9 with a wide range of diameters. In this process, thestationary round stock is moved against rotating lathetools at a certain feed rate. In this machine four cuttingtool carriages are attached to the circumference of theturrethead which are radially adjustable.Operating dataInput power 75 kW; speed n = 300...3,600 min –1 ;material O.D. 11...85 mm; feed rate 1...40 m/min.Bearing selectionThe main bearing arrangement is formed by two spindlebearings FAG B7036E.T.P4S.UL and accommodatesthe cutting forces transmitted by the four cuttingtools. The bearings are mounted in O arrangement andpreloaded with 14.5 kN (2 % of C 0 /Y 0 ) by means ofsprings.C 0 static load ratingY 0 thrust factor (static loading)Two angular contact ball bearings FAG71848MP.P5.UL in O arrangement accommodate theguiding loads from the axially displaceable hollowcone in which the four tool carriages are radiallyguided and adjusted.These bearings are also adjusted against each otherwith a spring preload of 5 kN (1 % of C 0 /Y 0 ).Experience shows that with these preloads no slippagedamage results, even if the rough-turning lathe isslowed down from 3,600 min –1 to zero within asecond.Machining tolerancesThe inner rings of both bearings are subjected to circumferentialloads and are fitted with a tolerance ofjs5.The bearing seats for the outer rings are machinedto G6. The spring preload remains effective in all operatingconditions as the expansion of the rotating partsdue to the effects of heat and centrifugal force do notcause jamming of the outer rings in the housing.Lubrication, sealingThe bearings are lubricated by oil injection lubricationwith ISO VG 32 (32 mm 2 /s at 40 °C). At 80 °C the oilhas an operating viscosity of = 8 mm 2 /s.An elaborate labyrinth seal protects the bearings fromthe ingress of cutting fluid and chips (rubbed-off particles)and from oil escape.21: Bearing arrangement of a rough-turning lathe for round bars and pipes33 FAG


22 Flywheel of a car body pressOperating dataInput power 33 kW; flywheel speed 370 min –1 ; radialload from flywheel weight and belt pull approximately26 kN.Bearing selectionBoth rings must be tightly fitted to their mating partsdue to the heavy loads and the circumferential load onthe outer ring. Nevertheless, mounting and dismountingshould be simple. These requirements can be metwith cylindrical roller bearings. They feature a highload carrying capacity, and they are separable, i.e. innerand outer rings can be mounted separately.The flywheel is supported on the hollow trunnion protrudingfrom the press frame by two cylindrical rollerbearings FAG NU1048M1A. The suffix M1A indicatesthat the bearings are fitted with an outer ring ridingmachined brass cage. Two angle rings HJ1048, oneat each of the outer sides of the cylindrical roller bearings,are provided for axial location of the flywheel.Spacer J is arranged between the bearing inner ringsand spacer A between the outer rings. Spacer J is0.6 +0.2 mm longer than spacer A, which ensures adequateaxial clearance. After the bearing has beenmounted, the axial clearance is checked (minimum0.4 mm).Bearing dimensioningThe trunnion diameter, which is determined by thedesign, determines in turn the bearing size.Machining tolerancesThe outer rings are subjected to circumferential loadand therefore require tight fits; the hub bore ismachined to M6. The inner rings are point-loaded. Thetrunnion is machined to j5.Bearing clearanceCalculations show that the radial clearance is reducedafter mounting, due to outer ring contraction andinner ring expansion (probable interference), by only20 µm from the value measurable prior to mounting(value indicated in table). Bearings of normal radialclearance (CN = 110...175 µm) can, therefore, be used.Lubrication, sealingGrease lubrication (FAG rolling bearing grease ArcanolL71V).Shaft seals prevent the ingress of dirt.FAG 34


22: Flywheel bearing arrangement of a car body press35 FAG


23 Vertical wood milling spindleOperating dataInput power 4 kW; nominal speed 12,000 min –1 .Maximum load on the work end bearing:radial – maximum cutting load of 0.9 kN,axial – shaft weight and spring preload of 0.2 kN.Maximum load on the drive end bearing:radial – maximum belt pull of 0.4 kN,axial – spring preload of 0.5 kN.Bearing selectionSince a simple bearing arrangement is required thebearing is not oil-lubricated as is normally the case forsuch high-speed applications. Experience has shownthat grease lubrication is effective if deep groove ballbearings of increased precision with textile laminatedphenolic resin cages are used. Where very high speedshave to be accommodated, angular contact ball bearingswith a small contact angle (spindle bearings) areoften provided. These bearings are interchangeablewith deep groove ball bearings and can, therefore, beemployed without modifying the spindle design.The work end features a deep groove ball bearing FAG6210TB.P63 and the drive end a deep groove ballbearing FAG 6208TB.P63. Two Belleville springwashers preload the bearings to 500 N. Clearance-freeoperation and high rigidity of the spindle system is,therefore, ensured. In addition to this, the spring preloadensures that both bearings are loaded under alloperating conditions, thus avoiding ball skiddingwhich may occur in unloaded bearings at high speeds,which in turn may cause roughening of the surfaces(increased running noise).As a rule, the bearings have to be relubricated every sixmonths, and for high speeds even more often.Non-rubbing labyrinth seals are used instead of rubbing-typeseals in order to avoid generation of additionalheat.Machining tolerancesSeat Diameter Cylindricity Axial runouttolerance tolerance tolerance of the(DIN ISO 1101) abutment shoulderShaft js5 IT2/2 IT2Housing JS6 IT3/2 IT3(work end)Housing H6 IT3/2 IT3(drive end)Work endBearing dimensioningThe size of the bearings is dictated by the shaft diameter,which in turn is based on the anticipated vibrations.The bearing sizes thus determined allow a sufficientbearing life to be achieved so that a contaminationfactor V = 0.5...0.3 can be assumed if great care wastaken to ensure cleanliness during mounting andmaintenance (relubrication). With this very good toutmost cleanliness the bearings even can be failsafe.Lubrication, sealingGrease lubrication with FAG rolling bearing greaseArcanol L74V. The bearings are packed with grease andreplenished at the required intervals. In view of thehigh speeds the grease quantities should not, however,be too large (careful regulation) so that a temperaturerise due to working of the grease is avoided.23: Vertical milling cutter spindleDrive endFAG 36


24 Double-shaft circular sawOperating dataInput power max. 200 kW;max. speed 2,940 min –1 .The cylindrical roller bearing FAG NU1026M at thedrive end is the floating bearing. Heat expansion in theaxial direction is freely accommodated in the bearing.The cylindrical roller bearing also accommodates thehigh belt pull tension forces.Bearing selectionA simple bearing arrangement is required with standardizedbearings which are suitable for very highspeeds and allow accurate shaft guidance. The requiredhigh shaft rigidity determines the bearing bore diameter.The locating bearing is at the work end in order to keepheat expansion in the axial direction as small as possibleat this end. The two spindle bearings FAGB7030E.T.P4S.UL are mounted in O arrangement.The bearings of the UL universal design are lightly preloadedby clamping the inner rings axially. The bearingpair is suitable for high speeds.Machining tolerancesShaft tolerance js5Housing tolerance JS6Lubrication, sealingThe bearings are greased for life, e.g. with FAG rollingbearing grease Arcanol L74V.Good sealing is required due to the dust arising duringsawing. Non-rubbing seals are used due to the highspeed. Flinger disks prevent the penetration of coarsecontaminants into the gap-type seals.24: Double-shaft circular saw37 FAG


25 Rolls for a plastic calenderPlastic foils are produced by means of calenders comprisingseveral rolls made of chilled cast iron or steelwith polished surfaces which are stacked on top ofeach other or arranged side by side.Hot oil or steam flows through the rolls, heating theO.D.s, depending on the material, to up to 220 °C(rigid PVC), which ensures a good processibility of thematerial. Rolls 1, 2 and 4 are subjected to deflectionunder the high loads in the rolling gap. In order to stillachieve the thickness tolerances of the sheets in the micrometerrange, the deflection is compensated for byinclining of rolls 1 and 3 and by counterbending ofrolls 2 and 4. Moreover, the narrow tolerance of thefoil thickness requires a high radial runout accuracy ofthe bearings and adequate radial guidance of roll 3which is only lightly loaded; this is achieved by preloadingthe main bearing arrangement by means ofcollaterally arranged, separate preloading bearings.Roll arrangement 1 to 41 234Operating dataType: four-roll calender, F-shapedUseful width 3,600 mmRoll diameter 820 mmRolling gap 1st step 1.5...2 mm2nd step 1...1.5 mm3rd step 0.25...1 mmRoll speed n = 6...24 min –1Inner ring temperature 170 °CRoll mass 18 t (weight ≈ 180 kN)Bearing systemTo accommodate the radial and thrust loads, the fourrolls are supported at both ends by the same type ofmain bearing arrangement. It consists of two doublerowcylindrical roller bearings forming the floatingbearing and of two double-row cylindrical roller bearingsplus one deep groove ball bearing forming thelocating bearing at the drive end. In addition, rolls 2and 4 have to accommodate counterbending forces,and roll 3 has to accommodate preloading forces.These counterbending and preloading forces are supportedat both roll ends in spherical roller bearings.Bearing selectionMain bearing arrangementThe radial pressure by load of 1,620 kN resulting fromthe maximum gap load of 4.5 kN/cm, as well as thecounterbending and preloading forces, are accommodatedby the main bearing arrangement at each end ofrolls 1, 2 and 4. The radial loads and the axial guidingloads are accommodated by double-row FAG cylindricalroller bearings (dimensions 500 x 650 x 130 mm)and deep groove ball bearings FAG 61996M.P65.At the locating bearing end the radially relieved deepgroove ball bearing accommodates only axial guidingloads.At the floating bearing end, heat expansions are compensatedby cylindrical roller bearings. Misalignmentsresulting from shaft deflections and roll inclination arecompensated for by providing a spherical recess for thebearing housings in the machine frame. The bearingsmust be dimensionally stable up to 200 °C as theirinner rings may heat up to 180 °C as a result of rollheating.The high radial runout accuracy (≤ 5 µm) is achievedby grinding the bearing inner rings and the roll bodyto finished size in one setting at a roll surface temperatureof 220 °C.The inner rings and the roll body canbe ground together due to the fact that the inner ringsof the cylindrical roller bearings – in contrast to thoseof spherical or tapered roller bearings – can be easilyremoved and mounted separately.The dimension of the inner ring raceway after grindinghas been selected such that no detrimental radialpreload is generated even during the heating processwhen the temperature difference between outer andinner ring is about 80 K.FAG 38


Rollbending bearingsA counterbending force is generated by means ofhydraulic jacks. The counterbending force (max.345 kN per bearing location) is transmitted to the rollneck by spherical roller bearings FAG23980BK.MB.C5. The bearings ensure low-frictionroll rotation and accommodate misalignments resultingfrom shaft deflection.Preloading bearingsThe main bearings of roll 3 have to accommodate thedifference from the rolling forces from rolls 2 and 4. Inorder to avoid uncontrolled radial roll movements, themain bearings are preloaded with 100 kN via sphericalroller bearings FAG 23888K.MB.C5.Bearing dimensioningTwo cylindrical roller bearings FAG 522028.. mountedside by side have a dynamic load rating of 2 x2,160 kN. The load accommodated by the bearings iscalculated, depending on the load direction, from (rollweight + press-on force + counterbending force)/2.The dimensioning calculation is carried out for themost heavily loaded roll 2 which rotates at an averagespeed of 15 min –1 .The nominal life is approx. 77,000 hours. Due to thehigh bearing temperature, the attainable life, whichtakes into account the amount of load, lubricant filmthickness, lubricant additives, cleanliness in the lubricatinggap and bearing type, is only 42,000 hours.The required bearing life of 40,000 h is reached.Machining tolerancesMain bearings:Guiding bearing:Preloading bearing:Rollbending bearing:LubricationShaft to r6/housing to H6Shaft to g6/housing radiallyrelievedShaft tapered/ housing H7Shaft tapered/ housing to H7The bearings are lubricated with oil. The lubricant hasto meet very stringent requirements. Due to the lowspeed and the high operating temperature, no elastohydrodynamiclubricant film can form. As a result, thebearings always operate in the mixed-friction rangeand are exposed to the risk of increased wear. This conditionrequires particularly suitable and tested lubricatingoils.A central circulation lubrication system with recoolingsupplies all bearings with oil. Holes in the bearinghousings, circumferential grooves in the bearing outerrings and in the spacers as well as radial grooves in theouter faces feed the oil directly into the bearings.Lip seals in the housing covers prevent dirt particlesfrom penetrating into the bearings.a Main bearing arrangement (radial), at each end of all rolls:2 cylindrical roller bearingsb Main bearing arrangement (axial), at the drive end of all rolls:1 deep groove ball bearing 61996M.P65c Preloading bearing arrangement, each end of roll 3:1 spherical roller bearing 23888K.MB.C5d Rollbending bearing arrangement, each end of rolls 2 and 4:1 spherical roller bearing 23980BK.MB.C5d c b a25: Bearing arrangement of a plastic calender39 FAG


26 Infinitely variable gearThe main components of this infinitely variable gearare two shafts linked by a chain which is guided by twobevelled drive disks at each of the shafts. By varyingthe distance between the bevelled drive disks the runningcircle of the chain increases or decreases, providingan infinitely variable transmission ratio.Bearing selectionThe two variator shafts are each supported by twodeep groove ball bearings FAG 6306.The driving torque is transmitted by sleeve M via ballsto the bevelled disk hub H. The ball contact surfaces ofcoupling K are wedge-shaped. Thus, sleeve and bevelleddisk hub are separated depending on the torquetransmitted, and subsequently the contact pressurebetween chain and disks is adapted to the torque.Two angular contact thrust ball bearings FAG751113M.P5 and one thrust ball bearing FAG51110.P5 accommodate the axial loads resulting fromthe contact pressure.Torque variations are associated with small relativemovements between shaft and drive disks; for this reasonthe two parts are separated by needle roller andcage assemblies (dimensions 37 x 45 x 26 mm).LubricationOil bath lubrication provides for ample oil supply tovariator components and bearings.Machining tolerancesBearing Seat Diameter Cylindricity tolerance Axial runout tolerancetolerance (DIN ISO 1101) of abutment shoulderDeep groove ball bearing Shaft k5 IT3/2 IT3Housing J6 IT3/2 IT3Angular contact thrust ball bearings Bevelled disk hubs/ k5 IT2/2 IT2and thrust ball bearing Sleeve IT3Needle roller and Shaft h5 IT3/2 IT3cage assembly Housing G6 IT3/2 IT326: Infinitely variable gearFAG 40


27 Spur gear transmission for a reversing rolling standOperating dataThe housing contains two three-step transmissions.The drive shafts (1) are at the same level on the outsideand the output shafts (4) are stacked in the housingcentre.Input speed 1,000 min –1 ; gear step-up 16.835:1;input power 2 x 3,950 kW.Bearing selectionInput shafts (1)One cylindrical roller bearing FAG NU2336M.C3and one four-point bearing FAG QJ336N2MPA.C3form the locating bearing. The floating bearing is a cylindricalroller bearing FAG NJ2336M.C3. The fourpointbearing is mounted with clearance in the housing(relieved) and, therefore, takes up just the axialloads. The two cylindrical roller bearings only take upthe radial loads.Intermediate shafts (2, 3)The intermediate shafts have a floating bearingarrangement with FAG spherical roller bearings:22348MB.C3 and 24160B.C3 for shafts 2.23280B.MB and 24164MB for shafts 3.Output shafts (4)A spherical roller bearing FAG 24096B.MB is used aslocating bearing. A full-complement single-row cylindricalroller bearing as a floating bearing compensatesfor the thermal length variations of the shaft.Machining tolerancesInput shafts (1):Cylindrical roller bearing: – Shaft n6; housing J6Four-point bearing: – Shaft n6; housing H7Intermediate shafts (2 and 3):Spherical roller bearing: – Shaft n6; housingrelief-turned.Output shafts (4):Cylindrical roller bearing: – Shaft p6; housing JS6Spherical roller bearing: – Shaft n6; housing JS6LubricationThe bearings are also connected to the oil circulationsystem for the transmission wheels. The oil (ISOVG320) is fed directly to the bearing positions fromthe oil filter.27: Spur gear transmission for a reversing rolling stand41 FAG


28 Marine reduction gearThe hardened and ground gearings of marine gearstransmit great torques.Operating dataInput power P = 5,475 kW; input speed 750 min –1 ;output speed 209 min –1 ; operating temperature ca.50 °C.Bearing selectionCoupling shaftThe coupling shaft (upper right) is supported at thedrive end by a spherical roller bearing 23248B.MB(locating bearing) and at the opposite end by a cylindricalroller bearing NU1056M (floating bearing). Theshaft transmits only the torque. The bearings have toaccommodate only the slight deadweights and minorgearwheel forces from a power take-off system. Thebearing dimensions are determined by the design; as aresult larger bearings are used than needed to accommodatethe loads. Consequently, a life calculation isnot required.Input shaftAt the input shaft the radial loads from the gearing areaccommodated by two spherical roller bearings23248B.MB. The thrust loads in the main sense of rotationduring headway operation are separately accommodatedby a spherical roller thrust bearing 29434E.The bearing 23248B.MB on the left side also accommodatesthe smaller axial loads in the opposite direction.It is adjusted against the spherical roller thrustbearing with a slight clearance and preloaded bysprings. The preload ensures that the thrust bearingrollers do not lift off the raceways when the loadchanges but keep rolling without slippage. The housingwasher of the spherical roller thrust bearing is notradially supported in the housing to ensure that thisbearing can transmit no radial loads.Output shaftAt the output shaft, radial and axial loads are accommodatedseparately. The radial loads are accommodatedby two spherical roller bearings 23068MB. In thelocating bearing position at the output end a sphericalroller thrust bearing 29464E accommodates the differencefrom the propeller thrust during headway operationand the axial tooth loads. The smaller axial loadsduring sternway operation are taken up by the smallerspherical roller thrust bearing 29364E. These twothrust bearings are also adjusted against each otherwith a slight axial clearance, preloaded by springs andnot radially supported in the housing.Bearing dimensioningBased on the operating data, the following nominalfatigue lives are obtained for the different bearings. Theminimum value of L h = 40,000 hours required for classificationwas not only reached but far exceeded.Shaft Bearing Rolling bearing Equivalent Index of Nominal Viscosity Factor Attainablelocation dynamic dynamic fatigue ratio life atload stressing life = a 23 = utmostP f L L h / 1 a 23II · s cleanliness[kN] [h] L hna [h]Coupling shaftLocating bearing 1 23248B.MB only slightly loaded by deadweightFloating bearing 2 NU1056M only slightly loaded by deadweightInput shaftRadial bearings 3 23248B.MB 242 3.98 49,900 6.3 >114 »200,0003 new 23048B.MB 242 1.88 4,100 5.8 >114 »200,0004 23248B.MB 186 5.18 120,000 6.3 >114 »200,000Thrust bearings 5 29434E 80 >6.03 >200,000 5.2 >114 »200,0005 new 29334E 80 4.91 102,000 5.0 >114 »200,000Output shaftRadial bearings 6 23068MB 158 >6.03 >200,000 2.4 >84 »200,0007 23068MB 293 4.64 83,500 2.4 >84 »200,0007 new 23968MB 293 2.70 13,600 2.3 39 »200,000Thrust bearings 8 29364E only briefly loaded during sternway operation9 29464E 650 3.81 43,300 2.5 > 87 »200,0009 new 29364E 650 2.35 8,600 2.3 > 84 »200,000FAG 42


The effects of basing the bearing dimensions on attainablelife become evident in the case of the two bearingsdimensioned for the least load carrying capacity: thespherical roller bearing 23248B.MB (bearing location3) at the coupling end of the input shaft and the sphericalroller thrust bearing 29464E (bearing location 9)at the output end of the output shaft.Based on the index of dynamic stressing f L a nominal lifeL h = 49,900 h is calculated for spherical roller bearing3 and L h = 43,300 h for spherical roller thrust bearing9. Due to the required minimum life of 40,000 h thetransmission bearings would thus be sufficiently dimensioned.28: Bearing arrangement of a marine gear43 FAG


Attainable lifeThe actually attainable life L hna is considerably longerthan the nominal life L h .L hna = a 1 · a 23 · L h is calculated with the following data:Nominal viscosity of the oil: 40 = 100 mm 2 /sOperating temperature: t = 50 °COperating viscosity: = 58 mm 2 /sSpherical roller bearing 23248B (no. 3):C = 2,450 kN; C 0 = 4,250 kN; n = 750 min –1 ;d m = (440 + 240)/2 = 340 mmRated viscosity: 1 = 9.2 mm 2 /sViscosity ratio: / 1 = 6.3Spherical roller thrust bearing 29464E (no. 9):C = 4,300 kN; C 0 = 15,600 kN; n = 209 min –1 ;d m = (580 + 320)/2 = 450 mmRated viscosity: 1 = 23 mm 2 /sViscosity ratio: = / 1 = 2.5A stress index f s* = C 0 /P 0* > 14 is obtained for bothbearings; consequently, K 1 = 1 and K 2 = 1; therefore,K = 1 + 1 = 2.From the viscosity ratio and the factor K the followingbasic factors are obtained:– for the radial spherical roller bearing a 23II = 3.8– for the spherical roller thrust bearing a 23II = 2.9Factor a 23 is obtained from a 23 = a 23II · s.The cleanliness factor s is determined on the basis of thecontamination factor V. Both bearings operate underutmost cleanliness conditions (V = 0.3). Cleanliness isutmost if the particle sizes and filtration ratios of contaminationfactor V = 0.3 are not exceeded.Taking into account the viscosity ratio and the stressindex f s* , a cleanliness factor of s > 30 and consequentlyan a 23 factor = a 23II · s > 114 and > 87, respectively, isobtained for the bearings under consideration. Theattainable life is in the endurance strength range.This means that smaller bearings could be provided forbearing locations 3, 5, 7 and 9 to accommodate thesame shaft diameter (see table: 3 new, 5 new, 7 new, 9new) and would, in spite of the now higher bearingloads, still be in the endurance strength range.Machining tolerancesAs all bearing inner rings in this application are subjectedto circumferential load they are fitted tightlyonto the shaft seats:– Radial bearings to n6– Thrust bearings to k6.If the radial bearing outer rings are subjected to pointload, the bearing seats in the housings are machined toH7.As the spherical roller thrust bearings are to accommodateexclusively thrust loads they are fitted with clearance,i.e. radially relieved, into the housing seats whichare machined to E8.Lubrication, sealingTo meet the high requirements on safety and reliability,adequate lubrication and cleanliness conditions areprovided for marine gears. The circulating oil ISO VG100, which is used to lubricate both gear wheels androlling bearings, is cooled and directly fed to the bearings.By-pass filters with filter condition indicators andwith an adequate filtration ratio ensure an oil conditionwhere no particles bigger than 75 µm are foundand where, consequently, cleanliness is usually utmost(contamination factor V = 0.3).For this reason, the oil cleanliness class should be14/11 or 15/12 (ISO 4406).Radial shaft seals protect the transmission from contamination.FAG 44


29 Bevel gear – spur gear transmissionOperating dataInput speed 1,000 min –1 ; gear ratio 6.25:1; inputpower 135 kW.Bearing selection, dimensioningPinion shaftThe pinion is an overhung arrangement. Two taperedroller bearings FAG 31315.A100.140.N11CA in Xarrangement are mounted at the locating end. Spacer Abetween the cups adjusts the bearing pair to achieve anaxial clearance of 100...140 µm prior to mounting.The floating bearing, a cylindrical roller bearing FAGNUP2315E.TVP2, has a tight fit on the shaft and aslide fit in the housing.Axial pinion adjustment is achieved by grinding thespacers B and C to suitable width.Crown wheel shaftThe crown wheel shaft is supported by two taperedroller bearings FAG 30320A (T2GB100 - DIN ISO355). The bearings are mounted in X arrangement andare adjusted through the cups. For axial adjustmentand adjustment of the axial clearance the spacers D andE are ground to suitable width.Output shaftThe output shaft is supported by two spherical rollerbearings FAG 23028ES.TVPB in floating bearingarrangement.Detrimental axial preloads are avoided by means of agap between the covers and outer rings.For the floating bearing of the pinion shaft an index ofdynamic stressing f L = 2.88 is calculated. This value correspondsto a nominal life of L h = 17,000 hours. Takinginto account the operating conditions such as:– oil ISO VG220 with suitable additives,– a good degree of cleanliness in the lubricating gap,– max. operating temperature 80 °C,a factor a 23 = 3 is obtained with the adjusted life calculation.Therefore, the attainable life L hna = 50,700 hours.Machining tolerancesThe bearing inner rings are subjected to circumferentialloads and consequently have to be fitted tightly on theshaft. The bearing seats for the pinion bearings mustbe machined to the following tolerances: Shaft tom5 / housing to H6.Lubrication, sealingAll bearings are sufficiently lubricated with the splashoil from the gears. The tapered roller bearing pair issupplied with oil which is fed through ducts from collectingpockets in the upper housing part.Shaft seals are fitted at the shaft openings.29: Bevel gear-spur gear transmission45 FAG


30 Double-step spur gearOperating dataMax. input speed 1,500 min –1 ; gear ratio 6.25:1;output power 1,100 kW at a maximum speed of1,500 min –1 .Bearing selectionThe bearings supporting the three gear shafts are adjusted.Two tapered roller bearings FAG 32224A(T4FD120)*, two tapered roller bearings FAG30330A (T2GB150)* and two tapered roller bearingsFAG 30336 are used. The X arrangement chosenmeans that the cups are adjusted and the adjustingshims inserted between the cup and housing cover determinethe axial clearance. The same gear housing isalso used for gears transmitting higher power. In such acase larger bearings are used without sleeves.Machining tolerancesThe cones are subjected to circumferential load and are,therefore, fitted tightly on the shaft. The cups are subjectedto point load and can, therefore, have a loose fit.The bearing seats on the shafts are machined to m6,the housings to J7.The relatively loose fit in the housing simplifies cupadjustment.Lubrication, cooling, sealingThe lubrication system selected depends on the gearspeed, power, operating time and ambient temperature.For low power and low gear circumferentialspeeds, oil splash lubrication without extra cooling issufficient. Medium power often requires some extracooling. For high power and high gear circumferentialspeeds circulating oil lubrication (possibly with oilcooler) is provided. Detailed information on the rangeof application of lubrication system and oils in questionis available from gear manufacturers.The rolling bearings are lubricated with the same oil asthe gears; for this purpose baffle plates and collectinggrooves are provided in the transmission case to trapthe oil and feed it through the channels to the bearings.Gap-type seals with grooves and oil return channels inthe end covers provide adequate sealing at the shaftopenings. More sophisticated seals such as shaft seals(with dust lip, if necessary) are provided where ambientconditions are adverse.*) Designation according to DIN ISO 35530: Double-step spur gearFAG 46


31 Worm gear pairOperating dataInput power 3.7 kW; input speed 1,500 min –1 ; overallgear ratio 50:1.Bearing selectionWorm shaftThe worm shaft bearings are primarily axially loaded,the load direction changing with the direction of rotationof the worm. The radial loads acting on the bearingsare relatively small. A locating-flating bearingarrangement is selected.The locating bearing comprises two universal angularcontact ball bearings FAG 7310B.TVP.UA. Suffix UAindicates that the bearings can be mounted in any tandem,O or X arrangement. When the bearings arepaired in O or X arrangement and the shaft is machinedto j5 and the housing to J6, the bearings feature asmall clearance. The two angular contact ball bearingsare mounted in X arrangement. Depending on thedirection of rotation of the worm shaft, either one orthe other bearing accommodates the axial load.A cylindrical roller bearing FAG NU309E.TVP2 ismounted as the floating bearing.Worm gear shaftThe bearings of the worm gear shaft are mainly radiallyloaded; the axial loads are relatively low in comparison.A deep groove ball bearing FAG 6218 is thereforeprovided at the locating bearing end and a cylindricalroller bearing FAG NU218E.TVP2 at the floatingbearing end.Machining tolerancesAngular contact ball bearings: Shaft to j5; housing to J6Cylindrical roller bearings: Shaft to k5; housing to J6Deep groove ball bearing: Shaft to k5; housing to K6Lubrication, sealingThe worm gear and the bearings are oil-lubricated.The oil level should coincide with the lowest point ofthe worm teeth pitch circle diameter.The sealing rings at the shaft openings prevent oil fromescaping and offer adequate protection against contamination.31: Worm gear pair47 FAG


32–33 Automotive gearboxesDesignThe rolling bearings used in torque converters in vehicles(manual transmissions and transfer boxes) are custom-tailoredto this application. Depending on theload accommodation and speed requirements, deepgroove ball bearings – both unshielded and dirt-protected("clean bearings") –, cylindrical roller bearings,combined bearings and tapered roller bearings haveproven themselves in the main bearing locations. Theidlers are generally supported on needle roller and cageassemblies. The main bearing locations have locatingfloatingbearing designs, adjusted bearing or floatingbearing arrangements.Locating-floating bearing arrangementRadial loads are accommodated by both bearings whilethe axial load is taken up by the locating bearing. Withextreme axial loads the radial and axial loads may betaken up separately (axial bearing e. g. deep groove ballbearing or four-point bearing) at the locating bearingend.Adjusted bearing arrangementThe angular contact ball bearings or tapered rollerbearings are mounted in opposition to one another.The bearings, when running at operating temperature,should have zero clearance or even preload (narrowaxial guidance). Regulation of the axial clearance byaxial displacement of the bearing rings. Both bearingsaccommodate radial and axial loads.Floating bearing arrangementThe bearings (except for angular contact bearings, allbearing types may be used) accommodate both radialand axial loads, permitting, however, axial displacementof the shaft. This axial displaceability is such thatthe bearings are never preloaded, not even under adversethermal conditions.LubricationThe gear wheels of vehicle transmissions are all oil-lubricatedalmost without exception. For this reason oillubrication is usually also provided for the rolling bearingsin the transmission.Since the rolling bearings require only very little lubricant,the oil splashed from the gear wheels is normallysufficient for bearing lubrication. Only in cases wherethe splash oil does not reach the bearings may it benecessary to provide collecting pockets and feed ducts.On the other hand it is advisable to protect those bearingswhich run directly beside the gear wheel from excessiveoil supply, for example by means of a seal or abaffle plate.However, with joint lubrication of gear wheels andbearings care must be taken that the life-reducing contaminantsare filtered out of the oil circulation (costly).Dirt-protected bearingsIn order to keep these contaminants (rubbed-off particlesfrom the gears) out of the bearings as long as possible,manual transmissions for cars are fitted todaywith sealed, grease-lubricated deep groove ball bearingsor angular contact ball bearings (so-called dirt-protectedor "clean bearings").Since roller bearings are less affected by cycled particles,the dirt-protected design is not required in automotivegearboxes.Bearing selection and dimensioningThe bearing calculation is based on the maximum inputtorque with the corresponding speed, the gearingdata and the proportionate running times for the individualgear steps.Determination of the tooth loadsBased on the tangential load F t = M d / r a radial load(F r = F t · tan E ) and an axial load (F a = F t · tan ) arecalculated. Based on the distances at the individualshafts, the forces acting on the teeth are distributedover the individual bearing locations, also taking intoaccount the tilting moment caused by the tooth loadcomponent F a .Index of dynamic stressing f LUnsealed transmission bearings in medium-weight toheavy cars should have an f Lm value of 1.0...1.3, whereasthe f Lm value for dirt-protected bearings should be0.7...1.0.The bearing loads in the individual speeds and thetransmission bearings are calculated in detail by meansof computer programs.Attainable lifeThe lubricant in open ball bearings must be assumedto be moderately (contamination factor V = 2) to heavilycontaminated (V = 3) .With the usual transmission bearing stress indexes off s* ≈ 2...8, depending on the gear, a cleanliness factor ofs = 0.6...0.7 is obtained with V = 2, and s = 0.3...0.5with V = 3.Consequently, due to the effects of contamination by thetransmission oil, the reserve capacities of the unsealedball bearings (higher f Lm value) cannot be utilized. Onthe other hand, if dirt-protected ball bearings are used,FAG 48


at least normal cleanliness (contamination factor V = 1),in most cases improved cleanliness (V = 0.5) or evenutmost cleanliness (V = 0.3) can be achieved. Thus,with a viscosity ratio of = 1, a cleanliness factor s is obtainedwhich is between 1 and 3.So dirt-protected transmission bearings (deep grooveball bearings or angular contact ball bearings) reachlives which are up to six times longer than those of unsealedbearings running in the "contaminated" transmissionoil.Machining tolerancesAt all bearing locations the inner rings are subjected tocircumferential load and the outer rings to point load.The bearing seats on the shafts are machined toj6...m6 and those in the housings to M6...P6 (lightmetal) and to J6...K6 (grey-cast iron), respectively. Thetighter bearing fits in light-metal housings take intoaccount the differences in the thermal expansion oflight metal and steel.49 FAG


32 Passenger car transmissionOperating dataFive-speed transmission for passenger cars for a maximuminput torque of 170 N m at 4,500 min –1 ; the 5thspeed is an overdrive gear; light-metal housing.Gear ratios: 3.717 – 2.019 – 1.316 – 1.0 – 0.804Bearing selectionInput shaftCombined bearings (deep groove ball bearing + rollerand cage assembly) as locating bearing for accommodatingradial and axial loads. The roller and cageassembly runs directly on the input shaft. The outerring is axially located via the housing cover in pulloperation and via a snap ring in push operation.Lay shaftFloating bearing arrangement with roller sleeves. Theaxial clearance is adjusted by means of fitting washersat the roller sleeve of the input end. Axial location isprovided by a snap ring. The transmission is sealed toprevent oil escape. There is an opening at the closedend of the output-side roller sleeve to facilitate dismounting.Output shaftEngine-end bearing:The roller and cage assembly runs directly on the outputshaft and in the bore of the input shaft. The cage isguided by the rolling elements. The logarithmic profileof the rollers is especially adapted to the stress resultingfrom shaft deflection. Lubricating holes in the gearwheel of the input shaft provide for a better oil supplyto the roller and cage assembly.Output end:Deep groove ball bearing as locating bearing, axial locationof the outer ring by means of the housing shoulderand retaining washer. The idlers on the outputshaft are directly supported by double-row needleroller-and-cageassemblies.Machining tolerancesBearingTolerancelocation Shaft HousingInput shaft k6 N6Direct bearing arrangementroller and cage assemblyg6Lay shaftDrive end/output end h5 N6Output shaftEngine-end bearing g6 G6Output end k6 N6Idlers(1st – 5th gear, reverse gear) h5 G632: Passenger car transmissionFAG 50


33 Manual gearbox for trucksOperating data16-speed-transmission for heavy trucks in the powerrange from 220 to 370 kW. The 4-speed component isextended to 16 gears by means of a split group and arange group.Gear ratios: 13.8 — 0.84 and 16.47 — 1.0.Bearing selectionInput and output shafts, main bearingsAdjusted tapered roller bearings in boxed X arrangement.Adjustment of these bearings via the cup of thetapered roller bearing at the input end. The cup ismachined to K6.Lay shaftTapered roller bearings in X arrangement; machiningtolerances: shaft to k6 / housing to K6.The idler gears are supported by needle-roller-andcageassemblies.First split constantBearing arrangement with two single-row needleroller-and-cageassemblies. Shaft tolerance g5; housingtolerance G5.Second split constantBearing arrangement with two cylindrical roller bearings,both outer ring raceways integrated in the gearwheelbore. The cylindrical roller bearings accommodateradial and axial loads.Range groupThe planet wheels are supported by full-complement,double-row cylindrical roller bearings.The lubricant is supplied via bores between the rollerrows and collecting pockets in the cage. A deep grooveball bearing supports the cage versus the ring gear.At the output end of the output shaft a deep grooveball bearing accommodates the radial and axial loadsresulting from the joint shaft.Split group Four-speed group with reverse gear Range group33: 16-speed truck transmission51 FAG


Automotive differentialsDesignSpiral bevel-gear drives – with or without intersectingaxes – are now almost always used for front and rearaxle drives. Very high axial loads arise which, withnon-intersecting axes, may be several times the tangentialload at the pinion. Due to the limited space andthe elevated torque values, the pinion bearings are veryheavily loaded. The pinion bearings should provide foreven meshing of pinion and crown wheel under load;therefore, the pinion bearing arrangement should be asrigid as possible. The pinion is either an overhung or astraddled arrangement. The overhung arrangement isusually fitted with two tapered roller bearings adjustedagainst one another. Compact bearing arrangements(double-row tapered roller bearings with an unsplitcup or a cup with a flange) are common.The crown wheel is mounted in common with the differential.The meshing accuracy of the teeth shouldvary as little as possible and mounting should, therefore,be provided with sufficient rigidity. The rigidityrequirements are easier to meet than with the pinionsince more mounting space is available for this applicationand the axial loads are generally lower.Bearing adjustmentRigid pinion and crown wheel guidance is achieved byadjusting the bearings against each other with a preload.With grey-cast iron housings, thermal expansionof the shaft increases the preload in nearly all cases afteroperating temperature is reached; the preload must,however, never be such as to exceed the elastic limit ofthe bearing material.The opposite applies to aluminium housings, whichare being used more and more because of their lightness.So, the preload has to be selected such as toachieve the required rigidity, but the additional bearingloading must not significantly reduce the bearinglife. This is the case if the axial preload does not exceedabout half the external axial force F a applied.LubricationDifferentials rely exclusively on oil lubrication. Bearingsand gears are lubricated with the same oil. Sincethe lubricant is subjected to severe stressing in the spiralgearing, hypoid oils with EP additives are used.While the splash oil sufficiently lubricates the crownwheel shaft bearings, which have to accommodate lowerloads, inlets and outlets must be provided for the oilfor the pinion shaft particularly for the bearing on theflange side. Attention should be paid to the oil flow directionwhich is always from the small end to the largeend of the tapered rollers. The oil ducts have to be arrangedand dimensioned such as to ensure that oil circulatesin every speed range.The pinion shaft is normally sealed by means of radialshaft seals, in some cases in combination with a flingersheet.Bearing dimensioningFatigue life analysis of the bearings mounted in differentialsis based on maximum torque and correspondingspeed as is the case with automotive gearboxes. Thepercentage times at the individual speeds are based onexperience. This information is then used to determinethe mean index of dynamic stressing. The rolling bearingsmounted in cars should have an average f Lm valueof 1...1.3.Wear of these bearings should be minimal since differentialdrives require a high guiding accuracy and asquiet running as possible. With today's bearing dimensioningthe service life of differential bearings is eitherterminated by fatigue or wear.A detailed calculation of the attainable life is usuallynot necessary as these bearings have proved their worthsufficiently in the automotive sector. Bearing dimensioningbased on a comparison calculation with theindex of dynamic stressing f L is sufficient.FAG 52


34 Final drive of a passenger carOperating dataMaximum engine torque 160 N m at 3,000 min –1 .Bearing selectionPinion shaftThe pinion shaft is fitted with FAG inch-dimensionedtapered roller bearings mounted in O arrangement.Dimensions: 34.925 x 72.233 x 25.4 mm (dynamicload rating C = 65.5 kN) and 30.163 x 68.263 x22.225 mm (C = 53 kN).The pinion is accurately positioned relative to thecrown wheel by means of shims inserted betweenhousing shoulder and bearing cup. The cones are circumferentiallyloaded. But only the cone of the largerbearing can be press-fitted. The cone of the smallerbearing is slide-fitted because the bearings are adjustedthrough this ring.Crown wheelCrown wheel and differential are mounted on thesame shaft. Fitted are two FAG inch-dimensionedtapered roller bearings of 38.1 x 68.288 x 20 mm;C = 39 kN.Both bearing and gear mesh adjustment are achieved bymeans of shims.Machining tolerancesPinion shaft:m6 (larger-size bearing)h6 (smaller-size bearing)housing P7Crown wheel: hollow shaft to r6housing to H6.To allow the pinion to be adjusted to a certain torqueand to avoid expensive fitting work (for instance machiningof a solid spacer), a thin-walled preformedsleeve is provided between the bearing cones. Thesleeve is somewhat longer than the maximum distancebetween the two bearing cones. Depending on thewidth tolerance values of the bearings there will besome elastic deformation of the sleeve (a few micronsat most).34: Final drive of a passenger car53 FAG


Lubrication, sealingWheel bearings are almost exclusively lubricated withgrease. Bearings which have no integrated seals are normallysealed with spring-preloaded shaft seals with specialdust lips. Sealed bearings such as the double-rowangular contact ball bearings with for-life lubrication,which are widespread in passenger cars, normally havea combination of dust shield and seal. Experience hasshown that these seals are satisfactory if the design providesan additional gap-type seal. Collecting groovesand baffles are also required to protect the bearingsagainst dust and splash water.35 Driven and steered front wheel of a front drive passenger carOperating dataWheel load 4,600 N; tyre size 175/70 R14;r dyn = 295 mm; maximum speed 180 km/h.Bearing selectionThe bearing arrangement is made up of a sealed double-rowFAG angular contact ball bearing.The bearing is greased for life with FAG rolling bearinggrease.The bearing arrangement of a driven and non-steeredrear wheel of a rear drive passenger car may also be designedlike this.35: Passenger-car front wheel55 FAG


Driven and non-steered rear wheel36 of a rear drive passenger carOperating dataWheel load 4,800 N; tyre size 195/65 VR15;r dyn = 315 mm; maximum speed 220 km/h.Bearing selectionThe wheel bearing arrangement consists of a doublerowFAG angular contact ball bearing which is greasedfor life.Seals and flinger rings provided on both sides protectthe bearing from contamination.Machining tolerancesThe inner rings and the outer ring of the bearing aretightly fitted.36: Passenger-car rear wheelFAG 56


37 Driven and non-steered rear wheel of a rear drive truckThe rear wheel hubs of heavy trucks often feature aplanetary gear. This type of drive provides a relativelyhigh gear ratio in a limited space. As the high drivingtorque is generated directly at the wheel, small differentialgears and light drive shafts are possible.Operating dataWheel load 100 kN; tyre size 13.00-20;r dyn = 569 mm; permissible maximum speed 80 km/h.Bearing selectionWheel bearingsTapered roller bearings FAG 32019XA (T4CC095 accordingto DIN ISO 355) and FAG 33021 (T2DE105according to DIN ISO 355). Since these bearings havea particularly low section height they require only asmall radial mounting space thus allowing light-weightconstructions. The relatively large bearing width andlong rollers result in a high load carrying capacity.The bearings are adjusted against each other in Oarrangement (large spread).Planetary gearsThe outer planet drive increases the driving torque in aminumum space. The planet gear bearing arrangementis of the full-complement type, i.e. it features two rowsof needle rollers. Axial guidance is provided by thrustwashers.Machining tolerancesDirect bearing arrangementwith needle rollers: shaft to h5; housing to G6Tapered roller bearing: shaft to j6; housing to N7LubricationCommon oil lubrication for planet drive and wheelbearings. An oiltight, welded housing protects gearand bearings against contamination.37: Rear wheel of a truck57 FAG


38 Steering king pin of a truckA variety of steering king pin mounting arrangementsare possible. The bearing arrangement with two adjustedtapered roller bearings for accommodating the axialloads is generally used in driven truck front wheels. Inother cases the axial loads are accommodated by thrustball bearings or tapered roller thrust bearings. Sincethe radial mounting space for king pin bearing mountingarrangements is usually very limited the radialloads (steering and guiding forces) are accommodatedby a plain bearing made of bronze and drawn cupneedle roller bearings which provide for easy steering.Mounting with a tapered roller thrust bearingThe shock loads on the steering king pin are very high.Therefore, the thrust bearing must have a high loadcarrying capacity and be mounted with zero clearanceor preload. As the king pin performs only slight slewingmotions no cage is required so that the number ofrolling elements and, consequently, the load carryingcapacity can be increased.The example features a full-complement tapered rollerthrust bearing as the thrust bearing. It has a profiledshaft-washer raceway and a flat housing-washer raceway.The sealed bearing is held together by a pressedsteel cap, which simplifies mounting.The bearing is filled with special grease; it can be relubricatedif necessary. Openings in the sealing lip andthe elasticity of the sealing material ensure the escapeof the spent grease.The clearance between the knuckle and the crossmember is compensated for by shims. In this way, thethrust bearing can have zero clearance at best, whichmeans higher shock-type loads. Experience has shownthat this can be taken into account by means of an impactfactor of f z = 5...6, in the case of adjusted taperedroller bearings with an impact factor of f z = 3...5.The shaft washer of tapered roller thrust bearings islocated by a relatively loose fit on the steering kin pin(g6); the housing washer has no radial guidance.38: Steering king pin of a truckFAG 58


39 Shock absorbing strut for the front axle of a carFront axles are being equipped more and more frequentlywith McPherson shock absorbing struts.When driving, the coil spring and the damping unit ofthe McPherson strut cause movements relative to thebody which are due to spring deflection and the degreeof lock. For comfort reasons and for easy handling,these slewing motions are supported either by rollingbearings or rubber elements. Deep groove ball bearingsbest meet all requirements.Bearing selectionRequirements– Accommodation of weights and high shock loads– Maintenance-free designVariants– Damping unit and spring coil rotate together –single path solution (fig. a). The spring coil loadsand the pulsating loads from the piston rod act onthe strut bearing.Possible bearing designs: Deep groove ball bearingsloaded axially (with cage or full-complement variantswith a fracture-split outer ring) or thrust ballbearings.– Movements of the shock absorber's piston rod andof coil spring are independent of each other – dualpath solution (fig. b).Direct connection of shock absorber's piston rod tothe body via a rubber element; coil spring supportedby a special thrust ball bearing or angular contactball bearing (spring seat bearing).Both variants meet all requirements concerning sealing,for-life lubrication and economic efficiency.ab39: Shock absorbing strut for the front axle of a car; a: single path solution; b: dual path solution59 FAG


40 Water pump for passenger car and truck enginesThe water pump provides for circulation of the coolingwater in the engine. Smaller and lighter pump designsare possible with ready-to-mount bearing units.Bearing selectionThe water pump bearing unit consists of the shaft anda common outer ring with raceways for rolling-elementand-cageassemblies. The example features one balland-cageassembly and one roller-and-cage assemblyeach mounted in a locating-floating bearing arrangement.The roller-cage assembly is designed as the floatingbearing at the side that is most heavily loaded bythe belt pull. The ball-cage assembly is the locatingbearing: in addition to the radial loads it also accommodatesthe thrust of the pump impeller.Machining tolerance, bearing clearanceThe outer ring is mounted into the housing with anR7 interference fit. The bearing clearance of the unit isselected to allow for a small operating clearance.Lubrication, sealingFor-life lubrication with a special rolling bearinggrease. Lip seals in the outer ring are provided on bothsides against grease escape. A spring loaded axial faceseal is fitted at the impeller end. Unavoidable waterleakage is drained to the outside through the outletbore.40: Water pump bearing unit for a truck engineFAG 60


41 Belt tensioner for passenger car enginesThe cam shafts of many four-cycle engines are drivenwith toothed belts from the crankshaft.The belt tension necessary for quiet running is providedby an FAG bearing unit. This tensioning pulleyunit consists of a journal with integral raceways, a ballcageassembly and an outer ring with the plastic injection-mouldedtensioning pulley.The screw bore for fastening the tensioning pulley tothe engine housing is eccentrically located so that thebelt tension can be applied by rotating the journal.The bearing unit is sealed on both sides and packedwith grease for life. Speed is approximately7,000 min –1 .41: Belt tensioner for passenger car engines61 FAG


42 Axle box roller bearings of an Intercity train carriageThe type of axle box roller bearings presented here isused for Intercity traffic in Europe.The bogie frame is supported on the bearing housingby a central coil spring, arranged above the bearings.The wheelsets are guided by plate-type guiding armswhich are bolted on one side.Operating dataDeadweight of the carriage plus maximum payload:64,000 kg; two bogies, each with two wheelsets, implies4 wheelsets per car.Resulting axle weight per wheelset: A = 64,000/4 =16,000 kg; weight of wheelset G R = 1,260 kg;acceleration due to gravity g = 9.81 m/s 2 ;supplementary factor for dynamic loads occurring duringoperation f z = 1.3;thrust factor for cylindrical roller bearings f a = 1;number of bearings per wheelset i R = 4.Thus the equivalent dynamic load per bearing is:P = (A – G R )/i R · g · f z · f aP = (16,000 – 1,260)/4 · 9.81 · 1.3 · 1 = 46,990 NP = 46.99 kNWheel diameter D R = 890 mm;maximum speed v max = 200 km/h (possible speed250 km/h).Bearing selectionCylindrical roller bearings installed as axle box rollerbearings offer important advantages:Mounting is simple and they are easy to check andmaintain in main inspections.Axial clearance is irrelevant for radial clearance. Cylindricalroller bearings are pure radial bearings, but thelips allow the safe accommodation of all thrust loads(guiding forces) occurring in operation.Of all the roller bearing types cylindrical roller bearingshave the lowest friction. Their speed suitability istherefore greater than in the case of other roller bearings.Cylindrical roller bearings do not, however, compensatefor misalignment between axle and bogie frame.Therefore misalignment must be corrected by angularfreedom of the housing.The same cylindrical roller bearings are used for passengercars and freight cars. This simplifies stockkeeping.Each axle box accommodates two cylindrical rollerbearings, one FAG WJ130x240TVP and one FAGWJP130x240P.TVP.The bearing dimensions (d x D x B) are 130 x 240 x80 mm; the dynamic load rating C of one bearing is540 kN.The nominal rating life (L h10 ) is checked in kilometreswhen dimensioning the axle box bearings:L h10km = (C/P) 3.33 · D · π = (540/46.99) 3.33 · 890 · π =3,397 · 2,497.6 ≈ 9.5 million kilometres.Under these conditions the bearings are sufficiently dimensioned.5 million kilometres (lower limit) appliestoday as a basis for dimensioning axle box bearings forpassenger train carriages.Machining tolerancesBearing inner rings carry circumferential load; thereforethey are press-fitted: axle journal p6, housing H7.Bearing clearanceThe tight fit expands the bearing inner rings which reducesradial clearance. The air stream cools the outerrings to a greater extent than the inner rings duringtravel which leads to a further reduction in radial clearance.Therefore the bearings have a radial clearance of120 to 160 microns.Lubrication, sealingThe bearings are lubricated with a lithium soap basegrease. Lamellar rings at the wheel side provide for effectivenon-rubbing sealing. A baffle plate at the coverend keeps the grease close to the bearing. Despite thesmall amount of grease (≈ 600 g) high running efficiency(800,000 km and more) can be reached due tothe polyamide cages without changing the lubricant.FAG 62


42: Axle box roller bearings of an Intercity train carriage63 FAG


43–44 UIC axle box roller bearings for freight carsThe car body is supported by laminated springs on thewheelset.The laminated springs have the additionaljob of guiding the wheelset. To limit the swaying motionof the car body and to accommodate the thrustpeaks, the housing features guiding surfaces in whichthe axle support of the frame is engaged. Cylindrical orspherical roller bearings are used as axle box rollerbearings. The housing boundary dimensions of theUIC bearing are standardized. According to the latestUIC conditions 130 mm diameter journals are specifiedfor cylindrical and spherical roller bearings. Insome cases 120 mm journals are used for cylindricalroller bearings.ClearanceThe tight fit expands the inner ring thus reducingradial clearance. A further clearance reduction resultsfrom the air stream developed during travel whichcools the outer ring more than the inner ring. Therefore,cylindrical roller bearings with a radial clearanceof 130 to 180 microns and spherical roller bearingswith increased radial clearance C3 are chosen.Lubrication, sealingThe axle box roller bearings are lubricated with a lithiumsoap base grease. Felt seals combined with a labyrinthhave proved most effective for cylindrical rollerbearings.UIC axle boxes with spherical roller bearings invariablyuse only labyrinth seals.Dimensioning, bearing selectionOperating data 43: UIC axle boxes with 44: UIC axle boxes withcylindrical roller bearings spherical roller bearingsDeadweight with max. payload G max 40,000 kg 40,000 kgTop speed v max 100 km/h 100 km/hWheel diameter D R 1 m 1 mNumber of wheelsets 2 2Wheelset weight G R 1,300 kg 1,300 kgWeight on axle A 20,000 kg 20,000 kgNumber of bearings per wheelset i R4 cylindrical roller bearings 4 spherical roller bearingsSupplementary factor f z · f a 1.3 · 1 = 1.3 1.3 · 1.25 = 1.625(f a = 1 for cylindrical roller bearings where thrust loadsare taken up by the lips;f a = 1.25 for spherical roller bearings where thrust loadsare taken up by the raceways.)Equivalent load:P = (A – G R ) · g · f z · f a /i R (g = 9.81 m/s 2 ) 59.6 kN 74.5 kNAverage travelling speed (v Fm = 0.75 · v max ) 75 km/h 75 km/hAverage wheelset speed n = 5,310 · v Fm (km/h)/D R (mm) 400 min –1 400 min –1Speed factor f n 0.475 0.475Index of dynamic stressing f L 3.5 3.5Required dynamic load rating of one bearing:C = f L /f n · P 439 kN 549 kNBearings mounted: Cylindrical roller bearings 2 spherical roller bearingsFAG WJ130x240TVP and FAG 502472AAFAG WJP130x240P.TVPBore x outside diameter x width 130 x 240 x 80 mm 130 x 220 x 73 mmDynamic load rating 540 kN 585 kNMachining tolerances of journals p6 p6Machining tolerances of housing bores H7 H7Radial clearance 130...180 µm Clearance group C3FAG 64


43: UIC axle boxes with cylindrical roller bearings44: UIC axle boxes with spherical roller bearings65 FAG


45Axle box roller bearingsof series 120's three-phase current locomotiveThe frame is supported by coil springs and spring seatswhich are integrated in the bearing housing. Thespring seats are arranged at different heights. The bearingis guided by an arm on each side which is linkeddiagonally to the housing. The arms are supported byelastic damping springs.Technical dataVehicle weight: 84,000 kgNumber of wheelsets: 4Wheelset weight: 2,250 kgAxle load: 22,000 kgSupplementary factor f z = 1.5The locomotive reaches top travelling speeds up to200 km/h.Bearing selectionPlease refer to example number 42 to determine theequivalent dynamic load P.Cylindrical roller bearings of the type NJ and NJPwith the dimensions 180 x 320 x 75 mm are mounted.Dynamic load rating of one bearing: C = 735 kN. Theouter and inner rings of both bearings are separated byspacer rings. The inner spacer ring is 2 mm wider thanthat of the outer rings.The axial clearance which arises thereby, is necessary tocompensate for bogie production tolerances. The bearingcan always be mounted without preload.Machining tolerancesThe bearing inner rings have circumferential load andare therefore given a tight fit: Journals to p6. The housingmaterial, an aluminium cast alloy, has a greater coefficientof expansion than cast steel which is why thetolerance field J7 was selected and not the housing toleranceH7 usually taken for cast steel housings.Bearing clearanceDue to the tight fit the bearing inner rings expand; theradial clearance becomes smaller. The outer ring iscooled more than the inner ring by the wind resistanceduring travel which leads to a further reduction ofclearance. For this reason bearings with increasedradial clearance C4 have been selected.Lubrication, sealingA lithium soap base grease is used for lubrication. Onthe wheel side the bearing is sealed by a two-web labyrinthseal. A V ring seal protects from contaminants onthe opposite side.45: Axle box roller bearings of series 120's three-phase current locomotiveFAG 66


46 Axle box roller bearings for the ICE driving unitThe bogie frame is supported by 2 coil springs each onthe bearing housings. The wheelset with the housingsis connected to the bogie by an arm. A setting mechanismenables the mounting of the wheelsets in thebogies without preload. The bearing units are axiallylocated by a cover.Operating dataAxle load: 19,900 kgWeight of unsprung weight: 2,090 kgDiameter of wheel 1,040 mmMaximum speed 250 to 280 km/h.Housing to:Bearing clearanceH7 (for GGG material)J7 (for aluminium alloys).A slight axial clearance is required for ideal running behaviourof the bogies at top speeds. It is between 0.2and 0.5 mm after mounting.Bearing selectionFAG tapered roller bearing units TAROL 150/250 aremounted in the wheelset housings of the series vehicleswith the designation ET 401. The main component ofthese units is a double row tapered roller bearing withthe dimensions: 150 x 250 x 160 mm.Machining tolerancesThe cones carry circumferential load and therefore havea tight fit: journal to p6.Lubrication, sealingThe TAROL 150 is supplied as a complete unit whichis sealed. The sealing system consists of two parallelouter diameter seated lamellar rings and one singleweblabyrinth acting as a pre-seal. The labyrinth isshaped as a seal cap and pressed into the cup.The seal caps are each provided with four dischargeholes through which excess grease escapes. This is particularlyimportant directly after relubrication. O ringsprotect the bearing unit from the penetration of waterin the seating area of the cup.46: Axle box roller bearings of the ICE driving unit67 FAG


47Axle box roller bearingsof the Channel tunnel's freight engine, class 92Class 92 is used for freight traffic in the Euro tunnelbetween Great Britain and the Continent. It is a twosystemengine which means it can be operated on directcurrent (750 V) as well as on alternating current(25 kV). The engine with six axles (CoCo) draws loadsweighing up to 1,600 t.The vertical loads of the bogie are accommodated bytwo lateral coil springs on the housing of the axle boxbearings. All lateral and longitudinal forces act via theguiding journals and sleeves which are attached to thebogie frame and the housing.The middle axle of each triple axle bogie is designed asa floating axle box to insure trouble-free operation innarrow curves. The two outer axles are designed asstandard axles as customary.Operating dataVehicle weight 126,000 kg; two bogies each with threeaxles; wheel diameter 1,120 mm; top speed v max =140 km/h;Power P = 5,000 kW at 25 kV AC4,000 kW at 750 V DCBearing selectionTapered roller bearing units TAROL 150/250 withpressed cages (JP) are mounted to the outer standardaxles of the vehicles. The bearings are clearance-adjusted,greased and sealed by the manufacturer. Fey lamellarrings provide for sealing on the side facing thewheel. A gap-type seal prevents rough dirt from penetratingthe bearings.The floating axle is accommodated in two cylindricalroller bearings whose dimensions are 150 x 250 x80 mm. The extended inner ring allows axial displacementwithin the bearing of ± 20 mm at a maximum.Sealing is achieved at the wheel end by means of longwebbedlabyrinths.Machining tolerancesThe inner rings carry circumferential load and have atight fit to p6 on the journal.The housing bores (point load ) are machined accordingto H7.Bearing clearancePrior to mounting, the TAROL units of the standardaxle have an axial clearance of 0.665...0.740 mm andthe cylindrical roller bearing units a radial clearance toC4 in order to compensate for heat expansion.LubricationBoth bearing types are lubricated with a lithium soapbase grease. While the lubricant in the TAROL bearingsis only changed during the main inspections, thefloating axle bearings must be relubricated in between.Due to the constant right to left displacement of theaxle lubricant is removed from the bearing area andtherefore has to be replaced regularly.FAG 68


47: Axle box roller bearings of the Channel tunnel's freight engine, class 9269 FAG


48 Axle box roller bearings for an underground trainA car has two bogies. Each axle box roller bearings iscushioned and guided by rubber-metal silent blocks.These are arranged between the axle box roller bearingand the frame opening. They are inclined to the verticaland have an angular cross-section.Machining tolerancesThe bearing inner rings carry circumferential load andare therefore given a tight fit: journal to m6, housingto H7.Operating dataWeight and maximum payload of one car: 34,000 kg.Number of wheelsets per bogie: 2.Wheelset weight G R : 1,400 kg.Supplementary factor f z : 1.3.Equivalent dynamic load P = 22.6 kN.Wheel diameter D R = 900 mm.Top speed v max = 80 km/h.Bearing selectionTwo cylindrical roller bearings are mounted per axlebox: One FAG NJ2318E.TVP2.C3.F2.H25 and oneFAG NJP2318ED.TVP2.C3.F2 (dynamic load ratingC = 430 kN).Bearing clearanceThe inner rings increase due to the tight fit: the radialclearance decreases. The outer rings are cooled morethan the inner rings due to the air stream during travel.This leads to a further reduction in clearance andtherefore a radial clearance C3 was selected.Lubrication, sealingA lithium soap base grease is used for lubrication. Acombination of a felt ring and a labrinth was selectedas a means of sealing.The labyrinth is provided with two axial webs since theaxle boxes are subjected to extreme dirt.48: Axle box roller bearings for an underground trainFAG 70


49 Axle box roller bearings for a city trainThe bogie frame is supported by Chevron springs onthe axle boxes.Operating dataThe equivalent dynamic load P m = 37 kN (calculatedfrom the various load conditions).Mean wheel diameter 640 mm.Maximum speed v max = 80 km/h.Bearing clearancePrior to mounting, the axial clearance of the bearingunit TAROL 90 is 530 – 630 microns.Machining tolerancesThe bearing cones carry circumferential load and aretherefore given a tight fit: journal n6.Bearing selectionThe main component of the FAG bearing unitsTAROL 90 used here is a double row tapered rollerbearing whose main dimensions are (d x D x B overallwidths cones/cup) 90 x 154 x 106/115 mm.Lubrication, sealingLubrication is with a lithium soap base grease. TheTAROL 90 is sealed at both ends with lamellar rings.The backing ring also has a collar which forms a gaptypeseal with the lid on the wheel side.49: Axle box roller bearings for a city train71 FAG


50Axle box roller bearingsaccording to AAR standard*) and modified typesThe FAG TAROL unit according to AAR standards isa compact bearing unit with a double row tapered rollerbearing as the main component. Seals at both sidesof the bearing, accessories and the grease filling makethe FAG TAROL a ready-to-mount unit. Neither isthe adjustment of the bearing clearance required. Theso-called NFL design (no field lubrication) is consideredstandard today. These TAROL units are no longerrelubricated during operation. The bearing grease isonly renewed during a main inspection.FAG use two types of seals: the rubbing radial shaft seal(fig. a) corresponds to the design used by AAR. Thenon-rubbing lamellar seal ring (fig. b) was developedby FAG and tested and approved by AAR.TAROL units do not have to be mounted into a housing.An adapter is attached between the TAROL unitand the bogie frame to transmit the loads and supportthe bearing cup on the loaded part of the circumference.FAG supply NARROW and WIDE adapters accordingto the AAR standards as well as special adapters designedfor the particular cases of application.a: Rubbing radial shaft sealAAR has stipulated the admissible loads for the varioussizes of TAROL units.Components of the FAG tapered roller bearing unitTAROL1 Locking plate2 Cap screw3 End cap4 Bearing cup5 Bearing cone with roller set6 Spacer7 Seal wear ring8 Seal9 Backing ringb: Non-rubbing lamellar sealFAG also supply TAROL units in metric dimensions.They (fig. c) have narrower tapered roller bearings andsmaller sealing and retaining components than theAAR design. The relevant journals are also shorter resultingin lower bending stresses with the same shaftdiameter than in the case of the AAR arrangement.Higher wheel loads are therefore admissible.21378 5 6 4 7 8 950: TAROL unitswith a double-row tapered roller bearing*) Association of American Railroadsc: TAROL units in metric dimensions and with short journal(SK design)FAG 72


51 Kiln trucks for sand lime brick worksOperating conditionsIn sand lime brick autoclaves the wheelset bearings ofthe kiln trucks are exposed for many hours to hotsteam of approximately 200 °C at 16 to 22 bars. Dueto corrosion hazard the bearing location should beprotected against penetration of the steam which isstrongly alkaline.BearingsSealing requires major attention when designing thebearing arrangement. The best solution is the use ofpulverized synthetic FAG sealing agent and solid lubricantArcanol DF. This lubricant is suitable for temperaturesranging between –200 °C and +300 °C and resistsalmost any chemical even at high temperatures. Itis non-ageing and water repellent. The powder ispacked into the bearing location penetrating into allcavities of the arrangement and forming a lubricatingfilm between balls and raceways, balls and cage andalso between outer ring and housing bore. The film inthe housing bore ensures easy bearing displaceability,even after prolonged operation. This protects the bearingagainst detrimental axial preload.In addition to lubrication Arcanol DF also acts as asealing agent. It settles in the sealing gaps of the axlepassage and protects the inside of the bearings againstthe ingress of alkaline condensate.The bearings are designed for a truck with two wheelsetsaccommodating a total weight F r of 43 kN.The bearing load for each bearing is relatively low atF r /4 allowing the use of inexpensive FAG6208.R200.250.S1 deep groove ball bearings.Considering the high operating temperatures thebearings have a particularly large radial clearance(200...250 or 250...350 microns), are heat-treatedaccording to S1 (200 °C) and are dimensionally stable.The bearings of the kiln trucks are mounted on theshaft as far as its shoulder by means of a punching capand fastened securely with a shaft end washer andscrew. They have a loose fit in the housing bore of theFAG series housing SUB6208. Two bolts attach thehousings to the frame of the trucks. Strips insertedbetween housing and frame compensate for any differencesin height due to warping of the truck frame.Machining tolerancesShaft: bearing seat j6.Housing: the diameter of bearing seat is between0.5 mm and 0.8 mm larger than the bearing O.D.SealingHeat-resistant aramide stuffing box packings seal thebearing area at the axle passage. The cover flange is alsoprovided with a heat-resistant seal.51: Kiln trucks for sand lime brick works73 FAG


52Universal quill drivefor threephase current locomotives of series 120All four wheelsets of series 120's threephase current locomotivesare driven. The traction motor arrangedtransversely to the direction of travel is connected tothe bogie at three points. The torque of the tractionmotor acts via pinion and bullgear on a universal quilldrive which is linked to the bullgear and driving wheelby the articulated lever coupling. The driving wheeltransmits the tractive force to the rails.Operating dataTop speed: 200 km/h; number of motors: 4; nominalpower per motor: 1,400 kW; motor speed: max.4,300 min –1 .Bearing selectionThe bullgear is supported on the universal quill drivein two tapered roller bearings FAG 534052 (dimensions:381.03 x 479.475 x 49.213 mm) which aremounted in O arrangement. Even with a small bearingdistance there is a relatively large spread and as a resulttilting rigidity is high.The quill drive housing is stationary. The cones, whichcarry point load, have a loose fit. The cups carry circumferentialload and have therefore a tight fit in therotating bullgear.The axial clearance of the bearing pair depends on themachining tolerances of the bearing seats and the operatingconditions. With inner and outer spacer sleevesbearing adjustment is not necessary when mounting.LubricationDuring mounting the bearings and the space betweenthe webs of the outer spacer sleeves are completelyfilled with a lithium soap base grease of the NLGI class2. They are relubricated after every 150,000 km. Thegrease is fed through the holes of the sleeve's web.52: Bullgear bearing arrangement for a universal quill driveFAG 74


53Suspension bearing arrangementfor electric goods train locomotiveThe torque of the traction motor is transmitted to thewheelset axle via pinion and bullgear. The traction motorarranged transversely to the direction of travel issupported directly on the wheelset axle in two bearinglocations. The reaction torque is taken up by anothersupport point at the bogie frame.Operating dataSix driven wheelsets, power per traction motor:500 kW. Max. speed: 100 km/h.Bearing selection, dimensioningFor a suspension bearing to have a long service life(nominal life over 2 million kilometres) roller bearingswith a high load carrying capacity are selected. A mediumdrive torque and a medium speed are taken as abasis for dimensioning. The index of dynamic stressingf L should be 3.5 at least. Usually it is well above it.Two FAG tapered roller bearings are mounted their dimensionsbeing 230.188 x 317.5 x 47.625 mm and231.775 x 336.55 x 65.088 mm. They are abundantlydimensioned because of the large shaft diameter. Highloads due to vibrations and shocks are accommodatedby special tapered roller bearings with reinforcedpressed cage (reduced number of rollers).Both tapered roller bearings are mounted in O arrangementwith little axial clearance (0.2...0.3 mm). Whenthe shaft has a maximum load the cups and cones aretilted by up to 3' against each other. The profile of thetapered rollers or raceways are modified (slightlycrowned) in order to avoid edge stressing.Machining tolerancesThe cups have circumferential load and an interferencefit on the shaft. The cup or the angle sleeve in thehousing is given a tight fit (perhaps a drive seat).Lubrication, sealingThe suspension bearings are lubricated with a lithiumsoap base grease of penetration class 3 with anti-corrosionadditives. Baffle plates hold the grease at the bearing(grease storage).The relubrication interval is about 200,000 to300,000 km depending on the type of operation.Labyrinth gap-type seals protect the bearing from contaminants.53: Suspension bearing arrangement for electric goods train locomotive75 FAG


54 Spur gear transmission for the underground or subwayThe drive of modern suburban vehicles should providefor a high degree of travel comfort, low noise, and beeconomical at the same time. These requirements arefulfilled by a new compact drive package which iscompletely supported on springs in the bogie.Operating dataTwo step parallel shaft drive, helical/double helicalgearing. Drive speed (input shaft) n max = 5,860 min –1 ,step-up i = 11.025.The drive motor is flanged on to the transmission. Auniversal joint coupling transmits the torque directlyto the wheelset from the transmission. The gearboxcase, which is split at axis height, is made of highstrengthcast aluminium. This is 25 % lighter thanspheroidal graphite cast iron.Bearing selectionInput shaftThe rotor of the drive motor is firmly attached to theinput shaft of the transmission. An elastic couplingwhich can be subject to bending, avoids constrainingforces in the shaft line which is supported in threepositions by a locating-floating bearing arrangement.The floating bearing in the motor is a cylindrical rollerbearing FAG NU212E (not illustrated). A secondfloating bearing, a cylindrical roller bearing FAGNJ215E, is at the motor end of the input shaft. Thelocating bearing arrangement of the input shaft is anangular contact ball bearing pair FAG 7215B.UA70 inX arrangement. Both angular contact ball bearings arefitted in an angle sleeve made of steel. Therefore differentheat expansion coefficients of steel and light metalcannot have a direct effect on the bearings.The bearings accommodate high speeds with a closeaxial guidance at the same time. This means tight fitsfor the bearing rings on the shaft and in the bore of theangle sleeve. The demand for a sufficient axial operatingclearance in addition to the tight fit is met with angularcontact ball bearings in universal design. The axialclearance of the bearing pair prior to mounting is70 microns.Intermediate shaftA spherical roller bearing FAG 22218E is mounted asthe locating bearing of the intermediate shaft. Its outerring is in a steel angle sleeve. The spherical roller bearingaccommodates chiefly axial forces from the gearing.The floating bearing, a cylindrical roller bearingFAG NJ2216E.C3, is directly in the light-metal housingwith the outer ring. The very tight fit in the housingnecessitates a bearing with increased radial clearance(C3).Output shaftThe output shaft whose large spur gear has a doublehelical gearing, is axially guided by the spherical rollerbearing of the intermediate shaft. The floating bearingarrangement with two cylindrical roller bearings FAGNUZ1848 is therefore sufficient for the output shaft.The NUZ design with an extended inner ring racewayallows a large axial displacement of the hollow shaft.Machining tolerancesAngular contact ballbearing pairSpherical roller bearingCylindrical roller bearing/intermediate shaftCylindrical roller bearing/output shaftLubricationShaft k5; pair housing K6Shaft m5; housing K6Shaft m5; housing N6Shaft n5; housingN6...P6All the bearings of the transmission are lubricated bythe oil circuit of the gearings.FAG 76


Output Antriebs-Hohlwelle hollow shaftZwischenwelleIntermediate shaftEingangswelleInput shaft54: Spur gear transmission for the underground or subway77 FAG


55 Bevel gear transmission for city trainsWith a so-called two-axled longitudinal drive in undergroundand metropolitan vehicles the traction motor(usually direct current motor) is arranged in the bogiein the direction of travel. A bevel gear transmission isflanged onto both sides of the motor's face. The driveunit firmly attached to the bogie frame is elasticallysupported by the wheel sets. The drive power is transmittedfrom the pinion shaft to the hollow ring gearshaft and then via rubber couplings to the drivingwheel shaft. This drive design leads to good runningbehaviour and moderate stressing for the traction motor,transmission and track superstructure.Machining tolerancesCylindrical roller bearing: Shaft m6, housing M6Tapered roller bearing/motor end:Shaft m6, sleeve M6Tapered roller bearingwith mantle ring: Shaft m6, ring R6 (S7)Tapered roller bearingof ring gear shaft: Shaft n6 – p6housing K6 – M6The axial clearance of the tapered roller bearing pairdepends on gearing and the operating conditions.Dimensioning, bearing selectionMean torques and speeds (hourly torque, hourlyspeed) are calculated from the tractive force – surfacespeed diagram and the time shares for the various runningconditions. By means of the gearing data thetooth loads of the hypoid bevel gear step are calculatedand, depending on the lever arms, are distributed tothe bearing locations.A life of 20,000 to 30,000 hours is assumed for bearingdimensioning. Assuming an average travel speed thiscorresponds to 1.2 – 1.3 million kilometers.To check the static safety of the bearings the maximumtorque (slippage torque) is taken as a basis.LubricationOil sump lubrication provides the transmission bearingswith lubricant. The flinger oil is conveyed via thering gear from the oil sump and fed directly to thetransmission bearings via oil collecting bowls and supplyducts. The special driving conditions for city trainsdemand highly doped oils which are resistant to heatand corrosion.Pinion shaftA single-row cylindrical roller bearing FAGNJ2224E.M1A.C3 (120 x 215 x 58 mm) is mountedas a floating bearing at the pinion end. It accommodatesthe high radial loads. The machined cage of thebearing is guided at the outer ring. The bearing has theincreased radial clearance C3 since the bearing ringshave a tight fit on the shaft and in the housing. Two taperedroller bearings FAG 31316 (80 x 170 x 42.5mm) are used as locating bearings. They are mounted inpairs in O arrangement. The bearing at the motor endaccommodates the radial loads as well as the axial loadsfrom the gearing; the other tapered roller bearing onlyaccommodates the axial loads arising during a changein direction of rotation. A minimum bearing load is arequirement in order to avoid harmful sliding motion(slippage) and premature wear. The cups of thetapered roller bearings are therefore preloaded withsprings.Ring gear shaftThere is a tapered roller bearing with the dimensions210 x 300 x 54.5 mm at each side of the ring gear.Both bearings are adjusted in X arrangement.55: Bevel gear transmission for city trainsFAG 78


56–60 Rudder shaftsThe rudders of ships make slow intermittent slewingmotions. The maximum slewing angle is about 35° toboth sides. The rudder shaft bearings accommodatethe radial and axial loads arising from the rudder andthe steering engine. The bearings are also subjected tothe vibrations created by the propeller jet. There arenumerous types of rudders the most common of whichare illustrated in figs. a to c.Rolling bearings are only used for the bearing positionsof the rudders inside ships. They are not suitable forthe bearing positions located outside the ship due tomounting difficulties and problems with sealing andlubricating. For such locations, plain bearings made ofstainless steel, bronze, plastic etc. are used and water ora mixture of grease and water is used for lubrication.a) Semi-spade rudder b) Spade-type rudder c) Steering nozzle79 FAG


56– 57 Spherical roller bearings as rudder shaft bearingsOperating dataAxial load 115 kN (weight of rudder and shaft), radialload 350 kN (driving force of steering engine andrudder).Bearing selection, dimensioningDue to the heavy loads and unavoidable misalignmentspherical roller bearings are used. They have a highload carrying capacity and are self-aligning. The ruddershaft diameter depends on size and speed of the ship aswell as on the type and size of the rudder used. Thebearing bore and the size of the bearing are determinedby the shaft diameter specified. A spherical roller bearingFAG 23052K.MB.R40.90 or FAG 23052K.MB.C2(radial clearance 150...220 microns) is mounted. Duringmounting the bearing inner ring is pressed ontothe tapered shaft seat so that the bearing operatesunder a light preload. Vibrations can thus be adequatelyaccommodated. The hydraulic method facilitatesdismounting particularly in the case of bearings withC2 bearing clearance. For this purpose the shaft musthave oil ducts and the tapered seat a circular groove.The housings of rudder shaft bearings FAGRS3052KS.1..... or FAG RS3052KW.1..... are made ofwelded shipbuilding steel plates.The static safety of a rudder shaft bearing is checkedbecause of the few slewing motions. An index of staticstressing f s between 4 and 5 is suitable for sphericalroller bearings.Machining tolerancesShaft taper 1 : 12, housing H7.Lubrication, sealingDuring mounting, the cavities of the spherical rollerbearings and housings are completely filled with lithiumsoap base grease of consistency number 2 which containsEP additives.Rudder shaft bearing FAG RS3052KS.1.....The bearing is grease lubricated. It sits in the pot-likehousing which is attached to the housing base plate bysturdy webs. A stuffing box seal is mounted in this baseplate. Its packing runs on a sleeve of seawater-resistantsteel.Due to the separation between the upper half and thebase any spray water which could penetrate runs alongthe side and does not get into the rolling bearing. Thestuffing box can be inspected at any time during operationand if necessary readjusted. The bottom end ofthe bearing is provided with a spring seal. A felt sealand V ring suffice for sealing at the top end. This bearingarrangement with stuffing box seal is maintenancefree.Rudder shaft bearing FAG RS3052KW.1.....Bearing and seal are in one and the same housing andare lubricated with grease. The bearing arrangementcan also be below the waterline. Sealing consists ofthree seawater-proof shaft sealing rings with an intermediategrease chamber. An automatic grease pumpholds the latter under permanent pressure.56: Rudder shaft bearing FAG RS3052KS.1..... 57: Rudder shaft bearing FAG RS3052KW.1.....FAG 80


58–59 Spherical roller thrust bearings as rudder carriersSpherical roller thrust bearings are used when the topbearing mainly has to take up the weight of the rudderand shaft. This is the case for all rudder drives notloaded by lateral forces, such as for rotary vane steeringgears and four-cylinder engines, which do not operatespade-type rudders.The two designs, N and W, for rudder carriers, differonly in their sealing.Bearing selection, dimensioningThe shaft diameter is determined according to formulaeof the Classification Societies. Thus the bore diameterof the rolling bearing is fixed. Due to the highaxial load carrying capacity a spherical roller thrustbearing FAG 29284E.MB with the dimensions 420 x580 x 95 mm is mounted directly on the shaft. Thebearing's index of static stressing f s ≥ 10.The welded housings are extraordinarily flat – theyprotrude just slightly beyond the deck or mountingbase. This provides advantages especially for largersteering engines, since the rudder shaft extension canbe kept short due to the low mounting and dismountingheight.Powerful springs under the bearing outer ring providea permanent positive contact of rollers and raceways.The supplementary plain bearing also accommodatesradial forces, if for example a cylinder in a four-cylindersteering engine fails.Machining tolerancesShaft h7. The housing is relief turned to ensure axialspring preload via the housing washer.Lubrication, sealingDuring mounting, the cavities of the spherical rollerthrust bearings and housings are completely filled withlithium soap base grease (consistency number 2 with EPadditives). As with radial spherical roller rudder bearings,there are also two designs (N and W) in the caseof rudder carrier bearings. Only the seal differs:FAG RS9284N.1..... rudder carrier bearings have feltseals, the rudder carrier bearings FAG RS9284W.1.....are sealed with seawater-proof shaft sealing rings.Both designs have a V-ring seal at the housing cover.58: Rudder carrier bearing FAG RS9284N.1..... 59: Rudder carrier bearing FAG RS9284W.1.....81 FAG


60 Spade-type rudderDesignThe slewing motion is accommodated by a top bearingand a bottom bearing. Both bearing locations areequipped with rolling bearings since they are inside theship's hull. The top bearing or rudder carrier is designedas the locating bearing due to the locating ringbetween cover and bearing outer ring. The bottombearing is the floating bearing. Spherical roller bearingsare used at both locations and the bearingarrangement is therefore statically defined and notaffected by misalignment of housing bores, warping ofthe ship's hull and rudder shaft deformation. Bothspherical roller bearings are mounted on adaptersleeves which are mounted and dismounted by meansof the hydraulic method. The relevant adapter sleeves(HG design) have connecting holes and grooves forthe pressure oil.Operating dataTop bearing:Axial load 380 kN (weight of rudder and shaft).Radial load 1,700 kN (load from rudder and steeringengine).Bottom bearing:Radial load 4,500 kN (load from rudder and steeringengine).Bearing selection, dimensioning, sealingBearing selection is based on the specified shaft diameterand the given loads. Since the bearings only makeslewing motions they are selected according to theirstatic load carrying capacity. An index of static stressingf s ≥ 4 is a must.The bottom spherical roller bearing, an FAG230/750K.MB.R60.210 (or 230/750K.MB.C2), islocated on an adapter sleeve FAG H30/750HG. Sincethis bearing is permanently below the waterline,special sealing must be provided for the shaft passage.The radial sealing rings run on a sleeve made of seawater-resistantsteel. The lips form a grease chamberpermanently pressurized by an automatic grease pump.Some of the grease (lithium soap base grease of the consistencynumber 2 with EP additives) penetrates intothe housing keeping the initial grease packing underconstant pressure.The seal above the bearing (shaft sealing ring and Vring) protects it against water which may either rundown the shaft or collect in the rudder trunk.The top spherical roller bearing, an FAG23188K.MB.R50.130 (or 23188K.MB.C2), ismounted on the shaft with an adapter sleeve FAGH3188HG. The adapter sleeve is fixed axially; belowby the shaft shoulder and above by a split holding ringwhich is bolted into a circular groove in the shaft. Thisupper bearing also takes up the weight from rudderand shaft as well as the radial loads. A shaft sealing ringis fitted at the upper and at the lower shaft diameterfor sealing purposes. There is also a V ring at the uppershaft passage.When relubricating with an automatic grease press, theinitial grease filling is kept under pressure and the sealrings are lubricated at the same time.Machining tolerancesRudder shaft h8, cylindricity tolerance IT5/2 (DINISO 1101). Housing H7.Bearing clearanceThe bearings have a particularly small radial clearance:the lower bearing has 60 to 210 microns or 390 to 570microns and the upper bearing has 50 to 130 micronsor 230 to 330 microns. During mounting, the bearingsare pressed onto the adapter sleeve so far that theyobtain a preload of 20 to 30 microns. With these preloadedbearings vibrations are easily accommodated.FAG 82


60: Spade-type rudder bearings83 FAG


61–62 Ship shaft bearings and stern tube bearingsThe propeller shaft of a ship is carried by so-called supportbearings. Since length variations of the shaft areconsiderable, particularly with long shafts, the bearingsmust have axial freedom. The last part of the shaft supportingthe propeller, runs in the so-called stern tubeor tail shaft bearings.Operating dataShaft diameter 560 mm; nominal speed of propellershaft 105 min –1 .Radial load from shaft and coupling 62 kN, no axialload – the propeller thrust is taken up by the propellerthrust block (figs. 63 and 64). With a supplementaryfactor of 100 % on the radial load (f z = 2), shocks orother dynamic forces are sufficiently taken into considerationwhen determining the bearing stress.Bearing selection, dimensioning, sealingSince the diameter of the ship shaft is specified, thebearings are overdimensioned for the loads to be accommodated.Thus the index of dynamic stressing f L rangesfrom 4 to 6 and therefore a high nominal life (L h ) is obtained.With very good cleanliness in the lubricatinggap, endurance strength is reached in the adjusted life calculation(L hna ) for ship shaft and stern tube bearings.A spherical roller bearing FAG 239/600BK.MB (dimensions600 x 800 x 150 mm, dynamic load rating C =3,450 kN) is used as ship shaft bearing. By means of thehydraulic method the bearing is attached to the shaftwith an adapter sleeve FAG H39/600HG and is locatedin a plummer block housing FAG SUC39/600H.1.....(fig. 61a). The housing is made of grey cast iron GG-25 and consists of a unsplit housing body with twosplit covers.The housing's sealing is provided for by the radial shaftsealing rings in the cover. For small quantities, weldedhousings are generally more economical than casthousings. Fig. 61b is an alternative ship shaft bearingarrangement made up of a spherical roller bearingFAG 23048K.MB with adapter sleeve H3048 and asplit plummer block housing S3048KBL.1.....(material GG-25).The ship shaft is surrounded by the stern tube at thestern. Fig. 62 shows a stern tube bearing arrangement,both bearings are designed as floating bearings. The tailbearing is also loaded by propeller weight and wave action.Spherical roller bearings are applied here alsowhose inner rings, with adapter sleeves, are attached tothe shaft. A special stern tube sealing protects the bearingsfrom seawater.Machining tolerancesThe inner rings carry circumferential load.Adapter sleeve seat on the shaft h8. Cylindricity toleranceIT5/2 (DIN ISO 1101); housing bore H7.Flanged housings are used for the tail shaft bearings.LubricationThe bearings are lubricated with a non-aging oil withEP additives (viscosity 150 to 300 mm 2 /s at 40°C). Thelower parts of the support bearing housings have viewingglasses or oil dip sticks on which the permissiblemaximum and minimum oil levels are marked. Thestern tube is filled with oil. The oil pressure is kept alittle higher than that of the surrounding water.61a: Ship shaft bearing; spherical roller bearing in SUC housingFAG 84


61b: Ship shaft bearing. Spherical roller bearing in S30.K housing62: Stern tube or tail shaft bearing arrangement85 FAG


63–64 Ship shaft thrust blocksThe thrust block is located directly behind a ship's engine.It transmits the propeller thrust to the ship.Apart from a small radial load from the shaft weightthe bearing is loaded by a purely concentric thrustload. Depending on the direction of rotation of thepropeller, it acts either forward or backward. Duringsternway the thrust load is lower and usually occursonly seldom. Three bearing arrangements are commonlyused for these requirements:Fig. 63a illustrates a thrust block arrangement withtwo spherical roller thrust bearings for small shaft diametersin a SGA plummer block housing.Fig. 63b illustrates a thrust block arrangement withtwo spherical roller thrust bearings and one radialspherical roller bearing in an FKA flanged housing.Both bearing arrangements are used when the axialload carrying capacity of a radial spherical roller bearingis insufficient when sternway is very frequent. Thespherical roller thrust bearings accommodate the propellerthrust during forward motion and the propellerpull during sternway. In 63a the thrust bearings accommodatethe weight also while in 63b the weight ofshaft and propeller is supported by a radial sphericalroller bearing.Fig. 64 shows ship shaft thrust blocks each with aspherical roller thrust bearing and a radial sphericalroller bearing:a: – in SGA housing, b: – in SUB housingThe curvature centres of the outer ring raceways of theradial and axial bearings coincide. The bearings aretherefore self-aligning and thus misalignment andbending of the shaft and hull are compensated for. Inthese thrust blocks only the propeller thrust is accommodatedby the spherical roller thrust bearing duringforward motion. The radial spherical roller bearingtransmits the weight of the shaft and the propeller pullduring sternway. The spherical roller thrust bearingnot under stress is preloaded by springs so that it doesnot lift during sternway. A constant axial minimumload is thus ensured.Machining tolerancesFig. 63a:Spherical roller thrust bearing Shaft m6; housing H7Fig. 63b:Spherical roller thrust bearing Shaft n6; housing reliefturnedRadial spherical roller bearing Shaft n6; housing F7Fig. 64a, 64b:Spherical roller thrust bearing Shaft m6; housing reliefturnedRadial spherical roller bearing Shaft m6; housing H7Dimensioning of bearingsThe diameter of the thrust block shaft is determinedaccording to the guidelines of the Classification Societies.Taking the power output into account the nominallife L h [h] and the resulting index of dynamic stressingf L are calculated. An f L value of 3 – 4 is recommendedfor the rolling bearings in ship shaft thrustblocks. Particularly with utmost cleanliness in the lubricatinggap, ship shaft thrust blocks reach endurancestrength according to the adjusted life calculation.DesignShip shaft thrust blocks are supplied as complete unitsFAG BEHT.DRL. The unit includes bearings, housingwith sealing and thrust block shaft with loose flange.The FAG thrust block housings are supplied either insplit design SGA (figs. 63a and 64a) or in unsplit designFKA (fig. 63b) or SUB (fig. 64b).Order example for unitFAG BEHT:GRL:110.156680, consisting of:1 Plummer block housing FAG SGA9322.1566781 Thrust block shaft with loose flangeFAG DRW110 x 610.1566782 Spherical roller thrust bearings FAG 29322E1 Locknut FAG KM261 Lock washer FAG MB26Oil lubricationFAG 86


Operating data63a: Ship shaft thrust block 63b: Ship shaft thrust block housing 64a, b: Ship shaft thrust blockFAG BEHT.DRL110.1..... with FAG FKA94/600.1 FAG BEHT.DRL.200.1..... with2 spherical roller thrust bearings 2 spherical roller thrust bearings 1 spherical roller thrust bearing1 radial spherical roller bearing 1 radial spherical roller bearingDiameter of thrust block shaft 110 mm 600/510 mm 200 mmPower 320 kW 11,400 kW 1,470 kWSpeed 800 min –1 150 min –1 500 min –1Thrust 55 kN 1,625 kN 170 kNForward motion 50 % 50 % 95 %Sternway 50 % 50 % 5 %Bearings mounted 2 x FAG 29322E 1 x FAG 239/600B.MB.C3 1 x FAG 23140B.MB2 x FAG 294/600E.MB 2 x 29340ELubrication Oil sump lubrication 1 ) Oil sump lubrication 1 ) Oil sump lubrication 1 )Sealing Shaft sealing rings Shaft sealing rings Shaft sealing rings1) Non-aging oil with pressure additives (viscosity 150 to 300 mm 2 /s at 40°C)63a: Complete ship shaft thrust block FAG BEHT.DRL.110.1..... (SGA plummer block housing)63b: Ship shaft thrust block with FKA flanged housing87 FAG


64a: Complete ship shaft thrust block FAG BEHT.DRL.200.1..... (SGA plummer block housing)64b: Complete ship shaft thrust block FAG BEHT.DRL.200.1..... (SUB pot-shaped housing)FAG 88


65–72 Paper MachinesModern paper machines are extensive plants which frequentlystretch well beyond 100 m in length and havenumerous rolls. The demand for utmost operationalreliability is priority number one when designing anddimensioning bearing locations: if trouble arises at justone roll the whole plant has to be shut down. For thisreason the bearings are designed for a far longer nominallife (index of dynamic stressing f L = 5...6) than inother industrial equipment. A high degree of cleanlinessin the bearings is decisive for a long service life.This demands utmost sealing reliability, particularlyagainst moisture, and design diversity based on thetype of roll in question.Lubrication also influences the bearing life greatly. Allroll bearings in modern paper machines are connectedto an oil circulation system for operational reliabilityand maintenance purposes. The bearings in the wetend section of older paper machines are still lubricatedwith grease (lower environmental temperatures).In the dryer section, bearings for rope sheaves, spreaderrolls and sometimes guide rolls are still lubricatedwith grease.Due to high temperatures in the area of the dryer roll,bearing lubrication is particularly critical. Thereforeoils of the viscosity class ISO VG 220 or 320 are used.Lightly doped mineral oils and synthetic oils are suitable(high ageing stability), which correspond to the requirementsfor dryer roll oils and have proven themselvesin the field or successfully stood dynamic testingon the FAG test rig FE8.Lubrication can be improved considerably (increasingthe operating viscosity) by insulating the hollow journalsof the dryer rolls and thus reducing the bearingtemperature.The following examples show the structure of somemain bearing locations in the paper industry, for examplerefiners, suction rolls, press rolls, dryer rolls, guiderolls, calender thermo rolls, anti-deflection rolls andspreader rolls.Wet end sectionlarge extent of waterenvironmental temperature < 50°CDryer section( ) ( )high humidityenvironmental temperature > 100°CFinishing groupSuction rollSpreader rollGuide rollThermo rollSpreader rollFormingrollSpreaderrollAnti-deflection rollDuoStabilizerrollDryerrollPaper guiderollAnti-deflectionrollForming sectionPress sectionA modern paper machine89 FAG


65 RefinersWood chips from the wood chopper which have beensoftened and steamed by water are broken down andcrushed in the refiner by means of crushing wheels rotatingin reverse motion with knife sections. Temperaturesup to 160 °C result from this process (steamedwood chips, crushing) and can lead to increased operatingtemperatures in bearings depending on theirconstruction.Operating dataAxial load from crushing process 400 kN;Radial load (rotor/shaft) 15 kN per bearing;Speed 600 min –1 ;Temperature in locating bearing 80 °C, in floatingbearing 70 °C.The right locating bearing only has a slight axial load(spring preload). The attainable life L hna is over200,000 h for this bearing.Machining tolerancesFloating bearing: The inner ring has circumferentialload and is attached to the tapered bearing seat of theshaft.Roundness tolerance IT5/2 (DIN ISO 1101);Taper angle tolerance AT7 (DIN 7178).Bearing seat of housing bore according to G7.Locating bearing: For mounting reasons, both shaft andhousing washer are in sleeves. The bearing seats aremachined according to k6 and G7 for the shaft sleevesand housing sleeves respectively.Bearing selection, dimensioningWith the high axial loads which have to be accommodated,an attainable life L hna ≥ 80,000 hours is required.A second thrust bearing is necessary since theaxial load acts mainly in the direction of the locatingbearing but can also be acting in the opposite direction.Thus the locating bearing arrangement is made upof two symmetrically arranged spherical roller thrustbearings FAG 29460E. For the rollers to remain undisturbedwhen the axial load is "reversed" both bearingsmust be preloaded with springs (minimum load) at theouter rings.A spherical roller bearing FAG 23052K.MB is mountedas a floating bearing and can easily accommodateshaft deflection. Thermal length variations of the shaftare compensated for in between bearing outer ring andhousing (sliding fit). The bearing is mounted directlyon the tapered shaft seat and fastened with a locknutHM3052.The floating bearing reaches a nominal life L h of wellover 200,000 hours. Excellent bearing lubrication isrequired due to slippage hazard when loads are low(P/C ≈ 0.02).A nominal life of L h = 50,600 h is calculated for the leftlocating bearing 29460E. With oil circulation lubrication,good cleanliness and a bearing temperature of70 °C, factor a 23 is 3.2. An attainable life L hna =162,000 h results from the adjusted life calculation.LubricationA lubricating oil ISO VG 150 with EP additives is usedfor locating and floating bearings.The radial spherical roller bearing has oil circulationlubrication with 0.8 l/min. Oil jet lubrication is providedfor the spherical roller thrust bearings. This ensuresadequate oil constantly at the highly-stressedcontact areas between roller face and lip. The oil issupplied through the side of the bearing via the spacersleeve. The minimum oil flow rate for both bearings is8 l/min (good heat dissipation from bearing). The oilis filtered in cirulation and cooled back to a temperatureof 40 °C.SealingThere are two labyrinths on the side of the crushingwheel connected to one another and filled with greasewhich protect the bearings from water and contaminationand prevent oil escaping from the bearings. Onthe outer side of the locating bearing a shaft sealing ringprevents oil escape.FAG 90


Floating bearingLocating bearing65: Refiner bearings91 FAG


66 Suction rollsSuction rolls are found in the wire or press section of apaper machine. They are hollow cylinders up to 10 min length which have several small holes all aroundtheir circumference. Some water is removed from theweb due to the rotating roll shell and the vacuum insidethe roll. The suction box, as interior axle, is stationary.The roll shell is driven by planet wheels inmodern paper machines.Operating dataRoll length 7,800 mm; roll diameter 1,600 mm; rotation278 min –1 (speed 1,400 m/min); roll weight270 kN; wire tension 5 kN/m.Bearing selection, dimensioningThe diameter of the suction box is decisive for the sizeof the bearing. We recommend bearings with a dynamicload rating as low as possible; the higher specificbearing load reduces the danger of slippage. Self-aligningbearings are necessary as misalignment could arise.Roll weight, wire tension and rotational speed are themain criteria for dimensioning the bearings.FAG spherical roller bearings FAG 239/850K.MB.C3with tapered bore (K 1:12) and increased radial clearanceare used. The bearings are mounted directly onthe tapered shaft seats for running accuracy reasons.The hydraulic method is applied to facilitate mounting.The locating bearing provides axial guidance for therolls while the floating bearing compensates for anyFloating bearinglength variations caused by displacement of the outerring in the housing bore.The nominal life for both bearings is L h > 100,000 h.The attainable life reaches over 200,000 h when theoperating temperature is 60 °C and oil ISO VG 68(viscosity ratio > 2; factor a 23 = 2.2) is used.Machining tolerancesThe inner ring has circumferential load and is attachedto the tapered bearing seat of the shaft.Roundness tolerance IT5/2 (DIN ISO 1101); taperangle tolerance AT7 (DIN 7178).Housing bores according to G7 due to point load at theouter ring.LubricationThe spherical roller bearings are supplied by circulationlubrication with a mineral oil quantity of 8 l/min.A mineral oil with sufficient viscosity and EP additives isselected. Additives with good anti-corrosive propertiesand water separation ability are also required. An effectivelubrication is achieved with an oil supply to thecentre of the bearing.SealingAny oil which escapes is thrown off via splash groovesinto oil collecting chambers and directed back. At theroll side a baffle plate and multiple grease-filled labyrinthwith integrated V ring prevent water penetratingfrom the outside.Locating bearing66: Suction roll bearingsFAG 92


67 Central press rollsThe paper web runs through the press rolls on a feltcloth and a large amount of water is pressed out of it.Modern press sections consist of one central press rollagainst which one or more (suction) press rolls arepressed. The central press roll is solid, made of granite/steelor steel with a protective coating.Operating dataRoll length 8,800 mm; roll diameter 1,500 mm; speed1,450 m/min; roll weight 750 kN. Pressure by 3 rollsat 30°, 180° and 210°; bearing temperature about60 °C. Direct drive.Bearing selection, dimensioningSelf-aligning spherical roller bearings of the series 231or 232 with a very high load carrying capacity are chosendue to the high radial load and the misalignmentwhich is possible between the bearing locations. A lowcross section height is also important for these bearingssince the height of the housing is restricted by the rolldiameter. The roll weight and the load components ofthe pressure rolls yield a resulting bearing load F r =300 kN.A spherical roller bearing FAG 231/600K.MB.C3 ismounted at every bearing location. The bearings withtapered bore (taper 1:12) are pressed directly onto thetapered shaft seat by means of the hydraulic method.The floating bearing at the operator's end permits temperature-dependinglength variations of the roll byshifting the outer ring in the housing. The locatingbearing is at the drive end.The nominal life calculated is L h > 100,000 h with aspeed of 308 min –1 . With good lubrication (viscosityratio ≈ 3, basic factor a 23II = 3) and improved cleanliness(contamination factor V = 0.5) in the lubricatinggap L hna 100,000 h according to the adjusted ratinglife calculation.Machining tolerancesThe inner ring has circumferential load and is attachedto the tapered bearing seat of the shaft.Roundness tolerance IT5/2 (DIN ISO 1101); taperangle tolerance AT7 (DIN 7178).Housing bores according to G7 since there is pointload at the outer ring.LubricationThe spherical roller bearings are supplied with a minimumoil quantity of 7 l/min by circulation lubrication.A mineral oil of sufficient viscosity (ISO VG 100) andEP additives is used. Additives with good anti-corrosiveproperties and water separation ability are also required.An effective lubrication is achieved with an oilsupply to the centre of the bearing.Oil returns to both sides of the bearing via oil collectingpockets and connecting holes.SealingOil splash grooves in the roll journal prevent oil escapingat the cover passage.Non-rubbing and maintenance free gap-type seals protectthe bearings from environmental influences.Locating bearingFloating bearing67: Central press roll bearings93 FAG


68 Dryer rollsThe remaining water in the dryer section is evaporated.The paper runs over numerous heated dryer rollsguided by endless dryer wires (formerly dryer felts).The dryer rolls are steam heated (temperature dependson the type of paper, its thickness and speed, and onthe number of dryer rolls). The high temperatures ofthe heating steam transfer to the bearing seats stressingthe rolling bearings accordingly. Today, the journalsthrough which the steam flows are insulated in orderto keep bearing temperatures low.Operating dataWorking width 5,700 mm; roll diameter 1,800 mm;paper speed 1,400 m/min (rotational speed 248 min –1 );heating temperature 165 °C (7 bar); roll weight 90 kN.Felt pull 4.5 kN/m; wrap angle 180°; environmentaltemperature under the dryer section hood approx.95 °C; insulated journal bores.Bearing selectionThe bearing load is calculated from the roll weight, feltpull and temporary water fill. The floating bearing isloaded with 75 kN, the locating bearing with 83 kNtaking into account the drive force. Heating the dryerroll leads to heat expansion which in turn leads to considerablechanges in length with such long rolls. Selfaligningrolling bearings are necessary due to the misalignmentarising between both bearing locations.A double-row cylindrical roller bearing of the dimensionseries 31 is provided as floating bearing at theoperator's end. It easily compensates for length variationsin the bearing between the rolls and the innerring raceway. With its spherical sliding surface a plainspherical bearing's seating ring accommodates anyalignment inaccuracy of the journal. A double-rowself-aligning cylindrical roller bearing FAG566487K.C5 with the dimensions 200x340x112 mmis mounted. A spherical roller bearing FAG23140BK.MB.C4 is mounted as locating bearing onthe drive end.Both bearings have about the same operating clearancein order to avoid any detrimental preload during theheating-up stage which may lead to a maximum temperaturedifference of 50 K. The spherical roller bearinghas an increased radial clearance according to C4(260...340 microns), the cylindrical roller bearing anincreased radial clearance according to C5 (275...330microns).Both bearings have a tapered bore (K 1:12) and aremounted by the hydraulic method directly onto thetapered journals.Since the cylindrical roller bearing and the sphericalroller bearing have the same dimensions unsplit PMDplummer block housings (FAG PMD3140AF or BF)are applied both at the drive end and at the operator'send.Due to increased operating temperature, both bearingsare given special heat treatment (isotemp) and are thusdimensionally stable up to 200 °C.Bearing dimensioningAn attainable life L hna ≥ 250,000 hours is required fordryer roll bearings. Lubrication decisively influencesthe adjusted rating life. Under an average operatingtemperature of 100°C the operating viscosity ≈16 mm 2 /s for a mineral oil with a nominal viscosity of220 mm 2 /s (ISO VG 220).The rated viscosity is determined from the speed andthe mean bearing diameter d m = (200 + 340)/2 =270 mm to 1 = 25 mm 2 /s.The viscosity ratio is then: = / 1 = 16/25 = 0.64.With the value K = 1 a basic factor a 23II = 1.1 is obtainedfor the spherical roller bearing.The values K = 0 and a 23II = 1.4 apply to the cylindricalroller bearing.With normal cleanliness (cleanliness factor s = 1) thefactor a 23 = a 23II · s1.1 for the spherical roller bearing,1.4 for the cylindrical roller bearing.The attainable life L hna = a 1 · a 23 · L h is therefore wellover 250,000 h for both bearings.Machining tolerancesThe inner rings have circumferential load and have atight fit on the tapered roll journal. The journals haveoil ducts so the bearings can be mounted and dismountedby means of the hydraulic method. Roundnesstolerance IT5/2 (DIN ISO 1101), taper angle toleranceAT7 (DIN 7178). Bearing seats in the housingbore according to G7.FAG 94


LubricationThe bearing housings are connected to a central oil circulationlubrication system so that heat is constantlydissipated from the bearing. High-grade mineral oilsISO VG 220 or 320 are used which must have a highoperating viscosity, thermal stability, good protectionagainst wear, good water separation ability and a highdegree of cleanliness. A minimum oil quantity of 1.6l/min is guided directly to the centre of the bearing viaa lubricating groove and lubricating holes in the outerring.The oil can be carried off at both sides of the bearingwith the central oil system. The danger of oil retentionand leakage is minimized considerably. Any contaminantsor wear particles which might penetrate thebearing are immediately washed out of it with thismethod of lubrication.SealingGap-tape seals, which are non-rubbing and maintenance-free,are provided as sealing for the journal passages.The oil is thrown off via splash grooves and oilcollecting chambers and flows back through returnholes to the two oil cavities on the housing floor. Coverseals make the housing of the paper machine oil proof.Locating bearingFloating bearing68: Dryer roll bearings95 FAG


69 Guide rollsGuide rolls guide, as the name indicates, and turn thewire and felt cloth in the wet end and dryer sections ofa paper machine. The same bearings are used for theguide rolls in both areas. Lubrication and sealing differ,however, depending on the place of application.In older machines the wet end section is usually lubricatedwith grease, and the dryer section with oil.In modern machines both sections have oil circulationlubrication. Due to different operating conditionsseparate oil circuits are necessary for the wet end anddryer sections.The larger the machine the more often it is found tobe faster. For this reason the bearing inner rings aremounted with a tapered bore directly on the taperedroll journal.Wet end sectionDepending on the positions of the bearings in the machinethey are subject to a small or large degree ofmoisture. Water must not penetrate the housing particularlywhen machines are being high-pressurecleaned.Dryer sectionEnvironmental temperatures of about 95 °C lead togreat length variations and place high demands onlubrication. The operating temperature of the bearingscan be 115 °C.Operating dataUseful width 8,800 mmRoll diameter 700 mmPaper speed 1,650 m/min (n = 750 min –1 )Roll weight F G ≈ 80 kNPaper pull 1 kN/m (tensile load F z ≈ 9 kN)Wrap angle 180°Bearing temperature approx. 105 °CBearing selection, dimensioningThe bearings must be able to accommodate loads andcompensate for misalignment at the same time (misalignment,bending). An increased radial clearanceaccording to C3 is necessary due to temperature differences.Spherical roller bearings FAG 22330EK.C3 aremounted.Bearing load:P = (F G + F z )/2 = (80 + 9)/2 = 44.5 kNThe diameter of the roll journal is determined by theroll rigidity required. As a result there is a high index ofdynamic stressing f L corresponding to a nominal life L hof well over 200,000 hours. The attainable life is evenhigher with such good lubrication conditions.The housings can be in standing or suspended positionor can be laterally screwed on. They are designed foroil circulation lubrication.Machining tolerancesThe inner rings have circumferential load and are directlyfitted to the tapered roll journal. The roll journalhave oil ducts so the bearings can be mounted and dismountedwith the hydraulic method.Roundness tolerance IT5/2 (DIN ISO 1101); taperangle tolerance AT7 (DIN 7178).Bearing seats in the housing bore according to G7.LubricationIn the dryer section: see example 68 (Dryer rolls) sincethe bearings are connected to the oil circuit of thedryer rolls. Minimum flow rate 0.9 l/min.In the wet end section: see example 66 (Suction rolls)and 67 (Central press rolls), since the bearings are connectedto the oil circuit of the wet section rolls.Minimum flow rate 0.5 l/min.SealingGap-type seals, which are non-rubbing and maintenance-free,prevent oil from escaping through the coverpassages in the dryer section.The bearings in the wet end section must have relubricatablelabyrinth seals to prevent water from penetrating.Remaining oil is thrown off by splash grooves intocollecting chambers and directed back. Cover sealsmake the housing oilproof.FAG 96


Floating bearingLocating bearing69: Guide roll bearings (dryer section)97 FAG


70 Calender thermo rollsThe paper passes through the so-called calender stackafter leaving the dryer section. Soft calenders smooththe surface of the paper thus improving its printability.The calender consists of two pairs of rolls. One calenderroll (steel) lies above a counter roll, another belowone. The counter roll is the so-called anti-deflectionroll (elastic material). Soft calender rolls can be heatedby water, steam, or oil. The gap or the "nip" pressuredepends on the type of paper.Operating dataUseful width approx. 7 mRotation 350 min –1 (speed 1,100 m/min)Heated by oil at 200...250 °CInsulated roll journalOperating temperature at bearing inner ring 130 °C.Requirements with respect to load carrying capacityand self-alignment are met by spherical roller bearings.The cross section height of the bearing is limited bythe diameter of the roll journal and roll shell. Therelatively wide spherical roller bearings FAG231/560AK.MB.C4.T52BW are mounted.The nominal life L h = 83,000 h with given loads andpercentages of time.With a lubricating oil ISO VG 220 the viscosity ratiois = 0.71 under an operating temperature of 130 °C.An attainable life L hna > 100,000 h is obtained with theadjusted rating life calculation (where f s* > 12; a 23II =1.2; V = 0.5; s = 1.6).The increased radial clearance C4 is required due tothe danger of detrimental radial preload in the bearingduring the heating up phase when the temperaturedifference is great. With a speed index n · d m =224,000 min –1 · mm we recommend bearings withincreased running accuracy according to specificationT52BW.Bearing selection, dimensioningThe radial bearing load depends on the application ofthe calender roll as lower or upper roll, on the weightF G and the variable pressure load with percentage oftime.P 1 = F G + F nip minP 2 = F G + F nip medP 3 = F G + F nip maxP 4 = F G – F nip minP 5 = F G – F nip medP 6 = F G – F nip max= 600 kN= 990 kN= 1,260 kN= 60 kN= 390 kN= 720 kNPercentages of time: P 1 , P 4 : 10 % eachP 2 , P 3 , P 5 , P 6 : 20 % eachThe sum of the roll weight and the nip load acts forthe application as bottom roll whereas their differenceacts for the application as top roll.Taking the maximum load for designing the bearingwould lead to overdimensioning (equivalent dynamicload P < 0.02 · dynamic load rating C) in the case ofapplication in the top roll. Slippage may occur withsuch a low load which in turn can lead to bearing damagewhen lubrication is inadequate. In order to avoidthis problem, smaller bearings with a smaller dynamicload rating C should be selected so that P/C > 0.02.The risk of breaking through the lubricating filmdrops with the smaller roller mass.Machining tolerancesThe inner rings have circumferential load and are directlyfitted on the tapered roll journal. The roll journalshave oil ducts so that the hydraulic method can beapplied for mounting and dismounting the bearings.Roundness tolerance IT5/2 (DIN ISO 1101), taperangle tolerance AT7 (DIN 7178).Bearing seats in the housing boring according to F7.LubricationOil circulation lubrication with a synthetic oil ISO VG220, suitable in quality, which has stood dynamic testingon the FAG test rig FE8.By supplying a large amount of oil to the centre of thebearing (minimum flow rate 12 l/min) heat dissipationis achieved as well as a low thermal stress of the oil.Any contaminants or wear particles are washed out ofthe bearing. Oil returns at both sides of the bearing viaoil collecting pockets and connecting holes.SealingAngle rings at the roll side prevent direct oil escape atthe cover holes. Remaining oil is thrown off by splashgrooves into collecting chambers and directed back.Cover seals make the housing oilproof.FAG 98


Floating bearingLocating bearing70: Calender thermo roll bearings99 FAG


71 Anti-deflection rollsAnti-deflection rolls are found in both the press sectionand in calenders. They provide for an even paperthickness across the web and a consistently high paperquality. The drive is at the locating bearing end. Itspower is transmitted via gearing and the hypoid teethcoupling to the roll shell.The adjustment roll is pressed against the mating roll(calender roll) under very high pressure. As a result themating roll is bent and the form of the roll shellchanged. The shell of the adjustment roll must adjustto this form.The anti-deflection roll consists of a stationary axleand a rotating roll shell. Control elements which canbe pressure-balanced separately are provided on theaxle. They support the roll shell hydrostatically andeffect its adjustment. The roll shell is shaped like thebent mating roll by the changing pressure giving thepaper an even thickness.Operating dataRoll length 9,300 mm; roll diameter 1,025 mm; rollweight 610 kN; shell weight 210 kN; pressure 700 kN;circumferential velocity 1,500 m/min (n = 470 min –1 );bearing temperature 55 °C.Bearing selection, dimensioningA service life of > 100,000 h is required. The bearingonly has a guidance function when in operation (withpressure and closed gap).Spherical roller bearings FAG 23096MB.T52BW(dynamic load rating C = 3,800 kN) are used.Floating bearingDue to the danger of slippage bearings of the series239 with a low load rating should be selected.The bearings are produced with a reduced radial runout(specification T52BW), since running inaccuracyof the rotating roll shell influences the quality of thepaper web.Machine tolerancesBearing seats on the axle according to f6 due to pointload for the inner rings.The outer rings have circumferential load and a tight fit;the bearing seats in the housings are machined to P6.LubricationWhen dynamic misalignment and/or slippage mayoccur, a very good lubrication system must always providea load-carrying lubricating film. The bearings aresupplied with the lubricating oil used for the hydraulicsystem (ISO VG 150 with EP additives). The oil is fedlaterally to the bearings via holes. In new designs andparticularly with heated rolls, the lubricating oil is fedvia lubricating holes in the inner ring directly to thebearing contact areas.The deep groove ball bearings of the transmission arrangedat the locating bearing side are supplied with oilvia a separate oil circuit.SealingThe bearings are sealed externally with a shaft seal. Tothe roll side a baffle plate provides for an oil reservoirin the bearing area.Locating bearing71: Anti-deflection roll bearingsFAG 100


72 Spreader rollsPaper webs transported in lengthwise direction tend tocreasing. Spreader rolls stretch or expand in cross directionthe webs running over them. They flattencreases and any middle or end parts of the web whichare loose. Spreader rolls consist of a stationary axlewhich is bent symmetric to its longitudinal axis, andaround which the roll shell rotates. Tube-shaped sectionsmake up the roll shell and are arranged to rotatefreely and have angular freedom. The sections adjust toone another in such a way that the bending form ofthe axle is reflected on the shell surface. Depending onthe case of application – wet end section, dryer section,or subsequent processing – the sections are made ofstainless steel or provided with a flexible coating (e.g.rubber).Operating dataRoll length 8,300 mm, consisting of 22 sections;weight/section plus wire or paper web pull at 30° wrapangle 2 kN/m; a radial load of just 0.5 kN per bearingresults therefrom.Rotation of roll shell 1,160 min –1 .Operating temperature in the wet end section 40 °C;in the dryer section and in subsequent processing withinfrared drying temperatures can reach 120 °C.Bearing selection, dimensioningWith rotating outer ring, extremely smooth running isrequired from the bearings since the sections in the wetend section and in the dryer section or subsequent processingare only driven by the wire tension and thepaper web respectively.High operational reliability is also necessary since thefailure of one bearing alone means that the wholespreader roll has to be dismounted.FAG 61936.C3 deep groove ball bearings are selected.The increased radial clearance C3 permits easy adjustmentof the sections. With the low load, the bearingshave a nominal life L h of well over 100,000 hours.Machining tolerancesAs the outer ring of the bearing rotates with the rollshell it is given a tight fit with M6 tolerance and is securedaxially by a snap ring.The inner ring has point load and is fitted to the shaftsleeve with h6. Due to the bent roll axle and for assemblyreasons the sleeve is loosely fitted and axially attachedwith a screw.LubricationThe bearings are greased for life, i.e. no relubrication isprovided for. The selection and filling quantity of lubricatinggrease is determined by the demand forsmooth running as well as a service life of up to fiveyears (8,000 operating hours per year). Low-frictiongreases (e.g. greases of class LG10 for the wet end section)are advantageous with high speeds and low loads.SealingNon-rubbing dust shields are used for sealing due tothe smooth running required. They are stuck to thebearing outer ring on both sides so the base oil centrifugedfrom the lubricating grease cannot escape. Roundcord seals also provide for oil tightness.72 Spreader roll bearings101 FAG


73 Run wheel of a material ropewayOperating dataSpeed n = 270 min –1 ; radial load F r = 8 kN. Thrustloads as guidance loads only, considered by 20 % ofthe radial load: K a = 1.6 kN.Bearing selectionEach run wheel is supported by two tapered rollerbearings FAG 30306A. The bearings are assembled inO arrangement which provides for a wider bearingspread than an X arrangement. The wider the spread,the lower the additional bearing load from thrust loadK a .Bearing dimensioningAs thrust load K a acts at the wheel circumference, itgenerates radial reaction forces at the bearing locations.Thus,F rA /Y = 6.1/1.9 = 3.2; F rB /Y = 1.9/1.9 = 1 andconsequently F rA /Y > F rB /YThe second condition proven isK a > 0.5 · (F rA /Y – F rB /Y) = 0.5 (3.2 – 1) = 1.1For calculation of bearing A the following thrust loadF aA must, therefore, be taken into account:F aA = K a + 0.5 · F rA /Y = 1.6 + 0.5 · 1.9/1.9 = 2.1 kNConsequently, the equivalent dynamic load P A of bearingA is:P A = 0.4 · F rA + Y F a = 0.4 · 6.1 + 1.9 · 2.1 = 6.45 kNWith this load, the indicated dynamic load rating andthe speed factor f n = 0.534 (n = 270 min –1 ) the index ofdynamic stressing.f L = C/P A · f n = 60/6.45 · 0.534 = 4.97This value corresponds to a nominal rating life of morethan 100,000 hours. Since this calculation is based onthe most unfavourable load conditions, the thrust loadacting constantly at its maximum and only in one direction,the bearing is adequately dimensioned with regardto fatigue life. The service life will probably be terminatedby wear, especially under adverse operatingconditions (high humidity, heavy contamination).The load carrying capacity of bearing B does not needto be checked since its loading is much less than thatof bearing A.Bearing A:F rA = F r /2 + K a · (D/2)/l = 4 + 1.6 · 125/95 = 6.1 kNThe thrust load K a = 1.6 kN acts toward bearing A.Bearing B:F rB = F r /2 – K a · (D/2)/l = 4 – 1.6 · 125/95 = 1.9 kNRadial loads acting on a shaft supported on two taperedroller bearings generate axial reaction loadswhich have to be considered in the calculation of theequivalent dynamic load. These internal loads togetherwith the external thrust loads should, therefore, be takeninto account for life calculation (see FAG catalogueWL 41 520, chapter "Tapered roller bearings").Data for tapered roller bearings FAG 30306A (designationto DIN ISO 355: T2FB030):dynamic load rating C = 60 kN,Thrust factor Y = Y A = Y B = 1.9.Machining tolerancesThe run wheel mounting is a so-called hub mounting,i.e. the run wheel, with the two cups, rotates about astationary shaft. The cups carry circumferential loadand are thus tight-fitted. The shaft is machined to h6,the hub bore to M6.Lubrication, sealingThe bearings and the free spaces have to be filled duringmounting with grease, e. g. FAG rolling bearinggrease Arcanol L186V. The grease filling will last forapproximately one year.In the example shown, the bearings are sealed byspring steel seals (Nilos rings).FAG 102


Rope73: Run wheel of a material ropeway103 FAG


74 Rope return sheaves of a passenger ropewayIn this example of a passenger ropeway, eight sheavesare installed at the mountain station and another eightat the valley station including the sheaves in the valleystation tensioning weight pit. The sheave diameters are2.8 and 3.3 meters.Bearing selection, dimensioningThe valley station sheaves and the tensioning weightsheaves are fitted with spherical roller bearings FAG22234E. The sheaves at the mountain station are supportedby spherical roller bearings FAG 22240B.MB.The load on the bearings FAG 22234E installed in thetensioning weight sheaves is P = 65 kN each; with adynamic load rating C = 1,100 kN and a speed factor f n= 0.838, corresponding to a speed of 60 min –1 , theindex of dynamic stressing:f L = C/P · f n = 1,100/65 · 0.838 = 14.2.This shows that the bearings are more than adequatelydimensioned with regard to fatigue life.The one-piece sleeve carrying the bearings allows convenientchanging of the rope sheaves.Machining tolerancesThe outer rings carry circumferential load and require,therefore, a tight fit. To safeguard the spherical rollerbearings against detrimental axial preloading, the designis of the floating mounting type. The outer ringsare securely locked via the two covers by means of aspacer ring. The centre lip of sleeve H is slightly narrowerthan the spacer so that the sheave can float axiallyon the sleeve via the loosely fitted inner rings. Thesleeve is locked to prevent it from rotating with the innerrings.Sleeve to g6; hub bore to M6;The sleeve has a sliding fit on the shaft.Lubrication, sealingGrease lubrication with FAG rolling bearing greaseArcanol L186V. Relubrication by means of lubricatingholes in the shaft.A shaft seal ring in the covers provides adequate protectionagainst contamination.FAG 104


74: Rope return sheaves of a passenger ropeway105 FAG


75 Rope sheave (underground mining)These sheaves are arranged in the head frames of thepits. The rope fastened to the cage runs from the drivesheave or the drum of the hoist into the mine by passingover the rope sheaves.Operating dataStatic rope load 452 kN; weight of rope sheave andshaft 75 kN; rope sheave diameter d S = 6.3 m; haulagespeed v = 20 m/s; wrap angle 140°.Acceleration forces are taken into account by assuming10 % of the static rope load.The recommended index of dynamic stressing f L is4...4.5. With 4.5, the nominal rating life is about75,000 hours. It should be borne in mind that only inrare cases the rope sheave bearings fail due to materialfatigue; usually their service life is terminated by wear.Thus, the required dynamic load rating C for the sphericalroller bearing is calculated as follows:C = f L /f n · P = 4.5/0.838 · 500 = 2,680 kNSpherical roller bearings FAG 23252BK.MB with adynamic load rating C = 2,900 kN were chosen.The bearings feature a high load carrying capacity andcompensate for potential housing misalignments, shaftdeflections and deformations of the head frame.452 kNAdditional load 10 %Sheave andshaft 75 kN452 kN1000 kNAdditional load 10 %Machining tolerancesOne bearing acts as the locating bearing, the other oneas the floating bearing. Both bearings have a taperedbore (K 1:12). They are mounted on the shaft journalwith withdrawal sleeves (FAG AH2352H). Mountingand dismounting is simplified by using the hydraulicmethod. For this purpose the withdrawal sleeves featureoil grooves and ducts. The spherical roller bearingsare supported by FAG plummer block housingsFS3252AHF and FS3252AHL.Bearing selection, dimensioningFrom the parallelogram of forces the resultant load isapproximately 1,000 kN. Since the two bearings aresymmetrically arranged, the radial load per bearing isP = 500 kN.Speed n = v · 60/(d S · π) = 20 · 60/(6.3 · 3.14) =60 min –1 ; this yields a speed factor f n = 0.838.Shaft journal to h6, cylindricity tolerance IT5/2 (DINISO 1101).Housing to H7.Lubrication, sealingGrease lubrication with FAG rolling bearing greaseArcanol L186V.A multiple labyrinth protects the bearings againstcontamination. Replenishment of labyrinth grease iseffected about every 4...6 weeks.FAG 106


Locating bearingFloating bearing75: Rope sheave (underground mining)107 FAG


76 Rope sheave of a pulley blockIn pulley blocks it is customary to arrange severalsheaves on a common shaft. To achieve minimumoverall pulley block width, the sheaves and their bearingsshould, therefore, be as compact as possible.Bearing selectionFor the rope sheaves of pulley blocks the wrap angle is180°. Thus the radial load on the bearing is twice therope pull. Thrust loads, resulting from a possible inclinedrope pull, and the moments caused by them arelow and can be neglected for bearing life calculation.Adequate bearing spread for load accommodation isachieved by mounting either two bearings or onedouble-row bearing. Deep groove ball bearings aresatisfactory for accommodating the loads in this application.The bearings are mounted on a sleeve, forming aready-to-mount unit with the sheave which can beeasily replaced.Lubrication, sealingThe sheave bearings are lubricated with lithium soapbase grease of penetration class 3 (Arcanol L71V). Highloads (load ratio P/C > 0.15) require a lithium soapbase grease of penetration class 2 and EP-additives(Arcanol L186V). One grease filling normally lasts forseveral years.The rope sheave in this example is sealed by springsteel seals (Nilos rings).Operating data and bearing dimensioningRope pull S40 kNBearing loadF = 2 · S80 kNSpeed n 30 min –1Speed factor f n 1.04Bearings mounted 2 deep groove ball bearingsFAG 6220Dynamic load rating C = 2 x 122 kNEquivalent dynamic load P = F/2 = 40 kNIndex of dynamic stressing f L = C/P · f n= 122/40 · 1.04 = 3.17Nominal rating life L h = 16,000 hUsually, an index of dynamic stressing f L = 2.5...3.5 isused for rope sheaves. This corresponds to a nominalrating life of 8,000 to 20,000 hours.Thus the bearings are adequately dimensioned comparedwith established field applications.Machining tolerancesThe mounting is a so-called hub mounting, i.e. thepulley, with the outer rings, rotates about a stationaryshaft. The outer rings carry circumferential load and arepress-fitted: hub to M7.The inner rings carry point load allowing a loose fit orsliding fit: shaft sleeve to g6 or h6.76: Rope pulleys with deep groove ball bearingsFAG 108


77–78 Gantry of a floating craneFloating cranes are used in harbours for transportationof heavy and bulky goods, in shipyards for repair workand for ship outfitting. Due to their mobility they arean ideal complement to stationary cranes.The pillar of the crane described is attached to theship. The slewing gantry with the crane superstructureis supported on the crane pillar. The bearing mountinghas to take up the weight of the superstructure and thepayload. Since the common centre of gravity of payloadand gantry is outside the pillar axis, a tilting momentis produced causing horizontal reaction forces inthe bearings at the upper and lower pillar end.At the upper pillar end the gantry runs on the so-calledpillar bearing mounting. It consists either of one singlespherical roller thrust bearing or one spherical rollerbearing combined with one spherical roller thrustbearing, depending on the amount of radial loading.GantryCrane pillar bearingCrane pillarRoller track assemblyAt the pillar foot the gantry is supported on a rollertrackassembly (see example no. 79).109 FAG


77 Crane pillar mounting with a spherical roller thrust bearingOperating dataThrust load (crane superstructure and payload) F a =6,200 kN; radial load (reaction forces resulting fromtilting moment and wind pressure) F r = 2,800 kN;speed n = 1 min –1 .Bearing selection, dimensioningThe thrust load, consisting of the weight of the slewingsuperstructure and the payload, is much higherthan the radial load resulting from the tilting momentand wind pressure. Therefore, the crane pillar bearingmust have a high thrust load carrying capacity. Moreover,the bearing must be self-aligning to compensatefor misalignment and elastic deformation unavoidableon these crane structures. Due to the low speed of1 min –1 the bearing is chosen with regard to its staticload carrying capacity.A spherical roller thrust bearing FAG 294/630E.MBwith a static load rating of C 0 = 58,500 kN; factor X 0 =2.7 is selected.For spherical roller thrust bearings under combinedload the ratio F r /F a must be small in order to ensurethat most of the rollers transmit loads. Condition:F r /F a ≤ 0.55.In this exampleF r /F a = 2,800/6,200 = 0.45Thus the equivalent static loadP 0 = F a + X 0 · F r = F a + 2.7 · F r= 6,200 + 2.7 · 2,800 = 13,800 kNThe index of static stressingf s = C 0 /P 0 = 58,500/13,800 = 4.24Thus, the requirement f s ≥ 4 for spherical roller thrustbearings (FAG catalogue WL 41 520) whose housingand shaft washers – as in this example – are fully supportedis met.With f s values ≥ 4...≤ 6 the shaft washer and the housingwasher must be fully supported axially, and goodradial support of the housing washer must also be provided.Machining tolerancesShaft washer to j6; housing washer to K7Lubrication, sealingOil bath lubrication, with the rollers fully immersed inoil. The oil level should be maintained to the upperedge of the shaft washer and is controlled by means ofan oil level indicator.Due to adverse ambient conditions existing for floatingcrane applications, high-efficiency seals must beprovided (oil-filled labyrinths). The inner and theouter labyrinth are interconnectd by oil holes. The oillevel in the labyrinths is also checked with an oil levelindicator.77: Crane pillar mounting with a spherical roller thrust bearingFAG 110


Crane pillar mounting with a spherical roller thrust bearing78 and a spherical roller bearingOperating dataThrust load (crane superstructure and payload) F a =1,700 kN; radial load (reaction forces resulting fromtilting moment and wind pressure) F r = 1,070 kN;speed n = 1 min –1 .Bearing selection, dimensioningIn this case F r /F a > 0.55. The radial load is relativelyhigh. Therefore, it is accommodated by an additionalradial bearing, a spherical roller bearing. The two bearingsare mounted so that their pivoting centres coincide.Thus angular alignability is ensured. A thrustwasher inserted between the two bearings prevents excessiveradial loading on the thrust bearing. The sphericalroller bearing size depends on that of the sphericalroller thrust bearing. The outside diameter of theradial bearing must be larger than the housing washerof the thrust bearing. To ensure close guidance of thecrane superstructure, the reduced radial clearance C2 isprovided for the radial bearing.Crane pillar mountings with one spherical roller bearingand one spherical roller thrust bearing providecompact designs. They require, however, a widermounting space than mountings with one singlespherical roller thrust bearing.The mounting features a spherical roller thrust bearingFAG 29440E with the static load rating C 0 = 8,500 kNand a spherical roller bearing FAG 23056B.MB.C2with the static load rating C 0 = 3,000 kN.For calculating the equivalent static load for the sphericalroller thrust bearing it is assumed that the frictionat the thrust washer, acting as a radial load, is 150 kN.Thus F r /F a < 0.55 for the spherical roller thrust bearing.Equivalent static load:P 0 = F a + X 0 · F r = F a + 2.7 · F r for F r ≤ 0.55 F a= 1,700 + 2.7 · 150 = 2,100 kNFor the spherical roller bearing:P 0 = F r = 1,070 kNHence the indices of static stressing f s = C 0 / P 0 are:Spherical roller thrust bearing = 8,500 / 2,100 = 4.05Spherical roller bearing = 3,000 / 1,070 = 2.8These values show that the bearings are safely dimensioned.The shaft washer and housing washer of spherical rollerthrust bearings with f s values of ≥ 4...≤ 6 must befully supported axially; good radial support of thehousing washer is also required.Machining tolerancesSpherical roller thrust bearing:Shaft washer to j6,housing washer to K7Spherical roller bearing:shaft to j6; housing to J7Lubrication, sealingThe bearing housing is filled with oil beyond the upperedge of the spherical roller bearing, i.e. the bearingsrun in an oil bath. Thus they are well protected againstcondensation water and corrosion.Outer sealing is provided by labyrinths. In view of theadverse ambient conditions an additional, rubbing sealwith elastic lip is provided. Inner sealing is effected bythe tube communicating with the housing, and a labyrinth.Thrust washer78: Crane pillar mounting with a spherical roller thrust bearing and a spherical roller bearing111 FAG


79 Roller track assemblyThe radial bearing mounting at the pillar foot consistsnormally of several rollers travelling on a circular track.Each of these rollers is supported by two bearings, theupper bearing being the locating bearing, the lower onethe floating bearing.f s = C 0 /P 0 = 1,630 / 1,100 = 1.48is calculated.This value meets the requirements for smooth runningof the bearing.Operating dataThe maximum load on one roller is 2,200 kN. Thus,each bearing is loaded with P 0 = 1,100 kN.Machining tolerancesThe inner rings carry circumferential load and are fittedtightly.Shaft to k6; housing to H7.Bearing selection, dimensioningThe rollers transmit only the horizontal loads resultingfrom the tilting moment. To cater for the misalignmentconditions inherent in structural steelwork andfor wheel axle deflection, self-aligning bearings have tobe provided.Spherical roller bearings FAG 23230ES.TVPB withstatic load rating C 0 = 1,630 kN are mounted.With an equivalent static load P 0 = 1,100 kN an indexof static stressingLubrication, sealingThe bearings and housing cavities are packed to capacitywith a lithium soap base grease with EP additives(FAG rolling bearing grease Arcanol L186V). Relubricationis possible through lubricating nipples in thehousing cover.Outer sealing is provided by the housing cover, innersealing by a shaft seal ring. A flinger ring between rollerand lower bearing additionally protects the lowershaft seal ring against dirt and rubbed-off particles.79: Roller-track assemblyFAG 112


Crane run wheelsBearings in crane run wheels have to accommodate theheavy loads resulting from the deadweight of the craneand the payload, and axial and radial reaction loadsresulting from the axial guiding loads between wheelflange and rail.113 FAG


80 Crane run wheelOperating dataWheel load R = 180 kN; operating speedn = 50 min –1 ; wheel diameter d 1 = 630 mm;bearing centres l = 186 mm.0.1 R0.1 RBearing dimensioningThe weight of the crane and the maximum payload areknown. The thrust acting between wheel and rail can,however, only be estimated. The equivalent dynamicload P acting on the bearings is calculated in accordancewith DIN 15 071; this standard specifies thethrust resulting from friction between wheel and rail tobe 10 % of the radial load. The bearing loads P I (bearingI) and P II (bearing II) are:P I = X · [R/2 + 0.1 · R · d 1 / (2 · l)]P II = X · [R/2 – 0.1 · R · d 1 / (2 · l)] + Y · 0.1 · RWith the radial factor X = 1 and e = 0.24 for F a /F r ≤ ethe thrust factor Y = 2.84.Thus P I = 90 + 18 · 630/372 = 120.5 kN = P maxBearing selection0.1 R0.1 RThe bearings fitted in run wheels are often designed ashub mountings. The run wheel rotates, together withthe bearing outer rings, about a stationary shaft.Spherical roller bearings are used because of their veryhigh load carrying capacity.The bearings fitted are two spherical roller bearingsFAG 22220E. The distance between the two bearingsshould not be too small in order to keep the bearingreaction loads resulting from the wheel-rail contactwithin reasonable limits.This bearing arrangement is standardized by DIN15 071. The two spherical roller bearings run on asleeve to allow for rapid replacement of the completerun wheel unit. It is a floating bearing arrangement, theinner rings being displaceable on the sleeve. Dependingon the thrust load direction, either the left-hand orthe right-hand bearing abuts the sleeve collar. Thisarrangement allows optimum bearing loading, sincethe bearing which accommodates the additional thrustloads is relieved of radial load due to the tiltingmoment from the thrust load.P II = 90 – 30.5 + 2.84 · 18 = 110.6 kN = P minAssuming that the bearing loads vary linearly betweenP min and P max ,P = (P min + 2 · P max )/3 = (110.6 + 241)/3 = 117.2 kNWith the dynamic load rating C = 360 kN and thespeed factor f n = 0.885 (n = 50 min –1 ) the index ofdynamic stressingf L = C/P · f n = 360/117.2 · 0.885 = 2.72With the generally recommended value for crane runwheels f L = 2.5...3.5, the bearing mounting is adequatelydimensioned.Machining tolerancesThe bearing outer rings, which carry circumferentialload, are tight fits. The hub is machined to M7, thesleeve to g6, thus providing for a slide fit for the innerrings. This prevents detrimental axial preloading andsimplifies bearing mounting and dismounting.Lubrication, sealingThe bearings are lubricated with a lithium soap basegrease with EP additives (FAG rolling bearing greaseArcanol L186V). The relubrication interval is approximatelyone year.Gap-type seals or simple rubbing seals are in most casessatisfactory.FAG 114


80: Crane run wheel with spherical roller bearings115 FAG


81 Crane hookThe load suspended from a crane hook often has to beswivelled before being lowered. Therefore, the hooksof heavy-duty cranes are designed for these swivellingmotions.Bearing selection, dimensioningSince the weight of the payload acts vertically downward,the load is pure thrust. Therefore, loose radialguidance of the shaft in the crosshead is satisfactory.The load carrying capacity of the bearing is based onits static load rating. A thrust ball bearing FAG51152FP with a static load rating C 0 = 1,020 kN ismounted. Based on the maximum hook load of1,000 kN plus a safety margin of 10 %, the index ofstatic stressing f s = C 0 /P 0 = 1,020 / 1,100 = 0.93; i. e.,permanent deformation occurs at maximum load.However, it is so small that it does not interfere withthe swivelling of the load.The bearing is adjusted against the collar at the hookshaft by means of a locknut. This prevents the shaftwasher from separating when the crane hook is set onthe ground.Machining tolerancesThe bearing seats are machined to j6 (washer) and toH7 (housing).Lubrication, sealingThe bearing assembly is packed to capacity withlithium soap base grease with EP additives (FAG rollingbearing grease Arcanol L186V). Maintenance of thebearing is not required. Above the crane hook nut asheet steel cap is provided which protects the bearingagainst contamination.81: Crane hook mountingFAG 116


82 Mast guidance bearings of a fork lift truckThe fork lift carriage must run smoothly in order tohandle the live loads efficiently. This requirement issatisfied by mast guide rollers and chain returnsheaves.Mast guide rollers (HMFR) and chain sheaves (KR) ofmodern fork lift trucks are largely fitted with doublerowangular contact ball bearings.Bearing selection, bearing designMast guide rollersFAG HMFR30x75x20.75 are preferably used for forkcarrier and lifting frame. They can accommodate radialloads, thrust loads and the moments resulting fromthese. The mast guide rollers feature thick-walled outerrings and can, therefore, accommodate even high,shock-type loads.The profile and dimensions of the outer ring are largelydictated by the standardized U-beam dimensions.Chain sheavesChain sheaves FAG KR30x75x28/27 are attached tothe hydraulically actuated upper section of the mastand serve to deflect the pull chain.Due to their relatively thick-walled outer ring, thebearings can accommodate high radial loads made upof the deadweight of the fork lift carriage, includingfork and live load. The outer ring profile is dictated bythe pull chain used; lateral guidance is provided by thetwo lips. The distance between the two ball rows, togetherwith the contact angle, provides for a wide spreadso that the return sheaves can also accommodate tiltingforces and axial guiding forces.Roller mounting is simple; they are simply placed onthe pin; axial preloading by a screw is not required.Chain return sheaves are axially locked.Machining tolerancesThe inner rings of der mast guide rollers and returnsheaves carry point load, thus a loose fit is satisfactory.The pin is machined to j6.Lubrication, sealingThe bearings are lubricated for life with a lithium soapbase grease (EP additives).Sealing is provided by single- or double-lip RSR seals.Mast guide rollerChain sheave82: Mast guide roller and chain return sheave for a fork lift truck117 FAG


83 Head pulley of a belt conveyorOne head pulley is not sufficient for very long belts,steeply inclined belts or heavily loaded belts. In suchcases several head pulleys are mounted in tandem. Inthis application, two head pulleys are arranged at thedrive station. Three identical driving motors are used:the first pulley is driven from both ends, the secondone from one end only.With an index of dynamic stressing f L ≈ 4 the bearingsare adequately dimensioned compared to field-provenbearing arrangements. Often the bearing life is limitedby wear on rolling elements and raceways and is generallyshorter than the nominal rating life (approx.50,000 h), calculated with the index of dynamic stressingf L . Improved cleanliness during mounting and operation,and a suitable lubricant, reduce wear, thus increasingthe bearing life. These influences are takeninto account in the adjusted rating life calculation bythe factor a 23 .Machining tolerancesOperating dataPower consumption 3 x 430 kW; belt width2,300 mm; belt speed 5.2 m/s; conveying capacity7,500 m 3 /h; pulley diameter 1,730 mm.Bearing selection, dimensioningThe shaft of the head pulley is supported on plummerblocks. The shaft diameter is dictated by strength considerations,thus determining the bearing bore andhousing size. Spherical roller bearings FAG23264K.MB are mounted. The one-piece plummerblock housings FAG BND3264K are made of caststeel GS-45. One of the plummer blocks acts as thelocating bearing, the other one as the floating bearing.To simplify mounting and dismounting hydraulicsleeves are used.The bearing inner rings carry circumferential load.They are fitted on the shaft with adapter sleeves FAGH3264HG.Shaft to h8 and cylindricity tolerance (DIN ISO1101) IT5/2; housing bore to H7.Lubrication, sealingGrease lubrication with a lithium soap base grease ofpenetration class 2 with EP additives (FAG rolling bearinggrease Arcanol L135V or L186V).The housing covers and rings on the shaft form nonrubbinglabyrinth seals. These multiple labyrinths arefilled with the same grease as the bearings and preventpenetration of foreign matter. In very dusty environmentsrelubrication at short intervals is required.Grease is injected into the bearing until some of thespent grease escapes from the labyrinths.FAG 118


83: Head pulley bearing arrangement of a belt conveyor119 FAG


Internal bearings for the tension/84 take-up pulley of a belt conveyorNon-driven pulleys in belt conveyors are frequently fittedwith internal bearings. The bearings are integratedinto the pulley so that the pulley body revolves aboutthe stationary shaft.Operating dataBelt width 3,000 mm; belt speed 6 m/s; pulley diameter1,000 mm; pulley load 1,650 kN.Bearing selection, dimensioningThese pulleys are supported either in two sphericalroller bearings (fig. a) or in two cylindrical roller bearings(fig. b). The internal design of the cylindrical rollerbearings allows the rolling elements to accommodateload-related shaft deflections without edge running.In a spherical roller bearing arrangement, an FAG23276BK.MB with an adapter sleeve FAGH3276HGJ is used as locating bearing and an FAG23276B.MB is used as floating bearing.In a cylindrical roller bearing arrangement, the floatingbearing is an FAG 547400A and the locating bearingan FAG 544975A. Both cylindrical roller bearingshave the main dimensions 360 x 680 x 240 mm andare interchangeable with spherical roller bearings FAG23276BK.MB with an adapter sleeve FAGH3276HGJ.The bearings must feature the required dynamic loadrating C/the required bore diameter. With an index ofdynamic stressing f L > 4, the bearings are sufficiently dimensionedwith regard to fatigue life.Often, the actual bearing life is considerably shorterthan the nominal rating life determined on the basis ofthe f L value. The cause is wear in raceways and on rollingelements as a result of adverse ambient conditions.Improved cleanliness during mounting and in operationas well as the utilization of a suitable lubricanthave a positive effect on the bearing life. These influencesare taken into account in the adjusted rating lifecalculation and in the modified life calculation in accordancewith DIN ISO 281. It is used for example tocompare the effects of different lubricants. The fatiguelife calculated for pulley bearings with this method inmost cases is not equivalent to the attainable life as theservice life is mainly limited by wear.Machining tolerancesIn view of the circumferential load and the relativelyhigh amount of load the outer rings must be a verytight fit in the pulley bore. Tolerances, see table below.Lubrication, sealingThe bearings are lubricated with a lithium soap basegrease of penetration 2 with EP additives (FAG rollingbearing grease Arcanol L186V).External sealing of the bearings is provided by nonrubbinglabyrinth seals or multi-collar rubbing seals. Inboth cases the labyrinths are filled with the same greaseas the bearings. To supply the bearings with freshgrease and to increase the sealing effect, relubrication iseffected at short intervals (depending on the amountof dirt) via the stationary shaft.Machining tolerancesBearing Seat Diameter tolerance Cylindricity toleranceSpherical roller bearing Shaft h8 IT5/2as locating bearing Pulley bore M7 IT5/2Spherical roller bearing Shaft g6 IT5/2as floating bearing Pulley bore M7 IT5/2Cylindrical roller bearing Shaft g6 IT5/2locating bearing, floating bearing Pulley bore N7 IT5/2FAG 120


ab84: Internal bearings for the tension / take-up pulley of a belt conveyor121 FAG


Belt conveyor idlersMany industries use belt conveyors for transportingbulk materials. The conveyors run on idlers and mayextend over many miles; thus the number of idlersneeded may be very large. Consequently, bearingmounting design is dictated by cost-saving considerations.Idler arrangementSmall belt conveyor systems feature idlers rigidlylinked to a frame. Large belt conveyor systems featureidler garlands linked to each other by flexible joints.85 Rigid idlersOperating dataCapacity I m = 2,500 t/h; Design: troughed belt withthree idlers per station; the two outer idlers are arrangedat an angle of 30° to the horizontal; distancebetween two idler stations l R = 1,200 mm; idler diameterd = 108 mm, belt weight G G = 35 kg/m, deadweightper roller G R = 6 kg; belt speed v = 3 m/s; accelerationdue to gravity g = 9.81 m/s 2 .Bearing selectionIdler mountings are usually internal bearing arrangements(hub mountings), i.e. the idler rotates about astationary shaft.Since a belt conveying plant requires a large number ofroller bearings, deep groove ball bearings, which areproduced in large quantities at low cost, are preferablyused. This allows a simple and economical idler design.Bearing dimensioningIdler speed n = v · 60 · 1,000 = 530 mind · π–1For ball bearings, the speed factor f n = 0.4.Load per idler station:F = g · l R · (I m + GG) =3.6 · v= 9,81 · 1,2 · (2,5003.6 · 3+ 35 )= 3,137 NFor a trough angle of 30° the horizontal centre idlertakes up approximately 65 % of this load. Thus theload on the centre idler isF R = 0.65 · F + g · G R = 0.65 · 3,137 + 9.81 · 6 == 2,100 N = 2.1 kNEquivalent dynamic bearing load:P = F r = F R /2 = 1.05 kNThe usual index of dynamic stressing for idler bearingsf L = 2.5...3.5. With f L = 3, the required dynamic loadrating C of a bearingC = f L · P/f n = 3 · 1.05/0.4 = 7.88 kNDeep groove ball bearings FAG 6204.2ZR.C3 havinga dynamic load rating C = 12.7 kN are mounted.a b c85a...c: Idler sealing variationsFAG 122


86 Idler garlandGenerally, the service life of a bearing is not terminatedby fatigue but by wear in raceways and on rolling elementsas a result of contamination. Increased cleanlinessduring mounting and efficient sealings increasethe bearing life. The ajdusted rating life calculation isused for comparing different seal designs.New idler bearings feature utmost cleanliness (V =0.3). However, in the course of operation the lubricantgets heavily contaminated by particles (V = 3).As the bearings in belt conveyor systems fail as a resultof wear, the values obtained by the adjusted rating lifecalculation (L hna ) usually are not equivalent to the actuallyattainable lives.In addition to the rigidly troughed belt conveyors thegarland type belt conveyors are being increasinglyused. The idlers of each station are linked to each otherby flexible joints. These joints may consist of a wirerope, a chain link (flat chain, round chain), hinge orsimilar.Idler garlands accommodate impacts elastically; in theevent of problems with a roller the individual garlandis lowered and can be replaced relatively easily if necessary.Machining tolerancesThe two deep groove ball bearings are mounted ontothe idler shaft in a floating bearing arrangement. As theinner rings are subjected to point load the shaft is machinedto h6 or js6. The outer rings are subjected tocircumferential load and are pressed, therefore, into theidler end with an M7 interference fit.Lubrication, sealing and maintenanceThe deep groove ball bearings FAG 6209.2ZR.C3 arepacked, at the manufacturing plant, with a lithiumsoap base grease of penetration class 2 which is sufficientfor the entire bearing service life. Such a grease isalso used for the sealing.With idler bearings, both the attainable life and the lubricantservice life may be considerably reduced bygrease contamination during operation so that the sealingselected is decisive. Figs. 85a...c show various typesof sealing for belt conveyor idlers.Simple seals (figs. 85a and b) are used for clean environments.Fig. 85c shows an idler seal for brown coalopen pit mining.Fig. 86 shows idler garlands connected by chain links.These idlers are part of a conveying installation forrock phosphate. The bearings fitted are deep grooveball bearings FAG 6303.2ZR.C3.Machining tolerancesIdler ends to M7, shaft to h6 or js6.Lubrication, sealing, maintenanceThe deep groove ball bearings (design .2ZR) are sealedby dust shields on both sides and filled with FAG rollingbearing grease, a lithium soap base grease of penetrationclass 2. The grease filling suffices for idler servicelife. A grease chamber with a non-rubbing labyrinthseal is provided at the outboard end. The second,adjacent chamber is closed by a shield pressed into thehub bore. A baffle plate protects the bearing againstcoarse particles.86: Idlers connected by chain link123 FAG


87 Bucket wheel shaft of a bucket wheel excavatorBucket wheel excavators are mainly used for browncoal open pit mining. The bucket wheel shaft carriesthe bucket wheel, the bull gear and the transmissionhousing. It is supported in the boom ends.Operating dataInput power 3 x 735 kW; theoretical conveying capacity130,000 m 3 / day; bucket wheel speed 3 min –1 .Bearing selectionThe bearings of the bucket wheel shaft are subjected tohigh shock-type loads. Moreover, shaft deflections andmisalignments must be expected. For this reason, onlyself-aligning roller bearings are suitable for supportingthe shaft. At both shaft ends, spherical roller bearingsFAG 239/900K.MB with withdrawal sleeves FAGAH39/900H are mounted as locating bearings. Thermallength variations of the shaft are compensated forby the elastic surrounding structure. The radial clearanceof the spherical roller bearings is eliminated duringmounting by pressing in the withdrawal sleeves.Only a split bearing can be provided on the bucketwheel side of the transmission box due to the solidforged shaft flange to which the bull gear is attached. Ifan unsplit bearing were to be provided on the oppositeside of the transmission box it could only be replacedafter dismounting the spherical roller bearing first.For this purpose the entire bucket wheel shaft wouldhave to be removed from the boom. This is avoided byusing a split FAG cylindrical roller bearing of dimensions1,000 x 1,220 x 170/100 mm on this side aswell. The increased axial clearance of the two cylindricalroller bearings yields a floating bearing arrangement.Each bearing accommodates axial guiding loads inonly one direction. The inner ring halves are attachedto the shaft by means of separate locking rings. Thecalculated nominal rating life of all bearings is over75,000 hours.Machining tolerancesAll inner rings are subjected to circumferential load.The spherical roller bearings FAG 239/900K.MB arehydraulically fastened to the shaft (machined to h8) bymeans of withdrawal sleeves FAG AH39/900H. Thesplit cylindrical roller bearings sit directly on the shaftwhich is machined to m6 in this place. All outer ringseats are toleranced to H7.Lubrication, sealingThe spherical roller bearings are oil-bath lubricated.The split cylindrical roller bearings are supplied by thedraining oil from gearwheel lubrication.The sealing is a combination of labyrinth and rubbingseal. The labyrinths at the spherical roller bearings canbe relubricated.87: Bucket wheel mountingFAG 124


88 Bottom sprocket of a bucket chain dredgerBucket chain dredgers perform dredging work inwaterways. The buckets are carried by a continuouschain from the bottom sprocket to the top sprocketover a large number of support rolls and back.Operating dataLadder length 32 m; number of buckets 44; maximumdredging depth approximately 14 m; radial load onbottom sprocket approximately 250 kN.Bearing selectionRugged operation and unvoidable misalignmentbetween the housings at both ends of the sprocketshaft call for self-aligning bearings. The bearings usedare spherical roller bearings FAG 22240B.MB. Bothbottom sprocket shaft bearings are designed as locatingbearings. However, the bearings are not nipped axially,the housing being mounted with clearance in its ladderyoke seat. For easier bearing dismounting the shaftjournal is provided with oilways and grooves for hydraulicdismounting.Machining tolerancesCircumferential load on the inner ring.Shaft journal to m6; housing to J7.Lubrication, sealingThe grease in the bearing (FAG rolling bearing greaseArcanol L186V) is renewed at intervals of 1 1/2 to 2years coinciding with the general overhaul period ofthe dredger.The bottom sprocket is constantly immersed in water.This requires waterproof sealing. Each bearing locationis, therefore, fitted with two rubbing seals (shaft sealswith bronze garter spring) and, in addition, with twopacking rings (stuffing box). The shaft seals run on abush of seawater-resistant material. The stuffing boxcan be retightened by means of a cover. Grease is regularlypumped into the labyrinth between the shaft sealsand packing rings.88: Bottom sprocket of a bucket chain dredger125 FAG


89 Drive unit of a finished goods elevatorFinished-goods elevators are used, for example, forcharging salt granulating plants. The material isconveyed in buckets attached to a chain. The chain isdriven by the tumbler situated at the upper end.Operating dataInput power 22 kW; speed 13.2 min –1 ; radial bearingload 90 kN.Bearing selectionAs shaft deflections and misalignments have to be expectedthe drive shaft is supported on self-aligningbearings. Selecting split spherical roller bearings FAG222SM125T ensures that the heavy drive unit withthe torque arm does not have to be dismounted in theevent of repair.As a result, the downtimes of the plant and the cost ofproduction loss are considerably lower than theywould be with one-piece bearings. To limit the varietyof bearings used, a split spherical roller bearing wasprovided at the free shaft end as well.Split spherical roller bearings have a cylindrical bore.Inner ring, outer ring and cage with roller set are splitinto halves.The split inner ring halves are braced together bymeans of four dowel screws and attached to the shaft.Both outer ring halves are fitted together without a gapby means of two dowel screws.The drive-end bearing is mounted with two locatingrings and acts as the locating bearing; the bearing at theopposite end is the floating bearing. Split spherical rollerbearings FAG 222SM125T are designed in such away that they can be mounted into split series housingsFAG SNV250 instead of one-piece spherical rollerbearings with an adapter sleeve. Outside diameter, outerring width and shaft seat diameter are identical.The theoretical fatigue life L h of the bearings is over100,000 hours.Machining tolerancesShaft to h6...h9;housing to H7Lubrication, sealingThe bearings are lubricated with grease. The housingsare connected to a central lubricating system so thatcontinuous relubrication is ensured.The shaft openings on both sides of the housing areeach sealed by a two-lip seal.89: Drive unit of a finished goods elevatorFAG 126


90 Driving axle of a construction machineModern construction machines feature planetary gearsin the wheel hub. This yields a considerable step-downratio in a limited space, in the example shown i g =6.35. As the considerable drive torque is generated immediatelyat the wheel, a light drive shaft is sufficient.Planet wheel bearing arrangementThe planet wheel bearings must provide a high loadcarrying capacity in a limited space. This is achievedby means of assemblies where the outer ring raceway isintegrated in the planet wheel. The self-aligning sphericalroller bearing selected in the example smoothlycompensates for small misalignments resulting fromthe deflection of the cantilever bearing journal underload. This yields a uniform contact pattern for thegearing, which is indicative of an optimal gear mesh.In the example shown the internal design of sphericalroller bearing FAG 22309E.TVPB is used.Wheel mountingAs a rule, the wheel mounting on rigid axles of constructionmachines consists of two tapered roller bearingswhich are axially adjusted against each other in Oarrangement (larger spread ) and with preload. In thisway, deformations and tilting of the planetary gear areminimized and impermissible plastic deformations(brinelling marks) resulting from adverse operatingconditions avoided.The wheel bearings are tapered roller bearings FAG32021X (in accordance with DIN ISO 355:T4DC105) and FAG 32024X (T4DC120).Machining tolerancesThe rotating outer rings of the wheel mounting aresubjected to circumferential load, the stationary innerrings to point load, therefore: journal to k6; hub to N7.Lubrication, sealingRolling bearings and gearing are washed around in therevolving wheel hub by the transmission oil.Radial shaft seals protect the bearings from dirt andsplash water.90: Driving axle of a construction machine127 FAG


91 Vibrating road rollerThe vibrations of such road rollers are produced by aneccentric shaft.Operating dataSpeed of eccentric shaft n = 1,800 min –1 ; radial loadF r = 238 kN; number of bearings z = 4; required nominalrating life L h ≥ 2,000 hours.Bearing selection, dimensioningThe centrifugal force from the imbalance weights onboth sides of the roll are accommodated by two bearingseach. The equivalent dynamic load per bearing is:P = 1/z · F r = 1/4 · F r = 59.5 kNFor the above conditions, an index of dynamic stressingf L = 1.52 and a speed factor of f n = 0.302 are obtained.The adverse dynamic stressing is taken into account byintroducing a supplementary factor f z = 1.2. Thus, therequired dynamic load rating of one bearingC = f L /f n · P · f z = 1.52/0.302 · 59.5 · 1.2 = 359.4 kNOn each side of the imbalance weights a cylindricalroller bearing FAG NJ320E.M1A.C4 (dynamic loadrating C = 380 kN) is mounted. Due to the vibratoryloads the bearings are fitted with an outer ring ridingmachined brass cage (M1A). The misalignmentbetween the two bearing locations from housingmachining inaccuracies is less than that permissible forcylindrical roller bearings.Machining tolerancesIn view of the vibrations it is advisable to provide tightfits for both the bearing inner and outer rings. Axialguidance of the eccentric shaft is provided by the lipsof the cylindrical roller bearings.Eccentric shaft to k5, housing bore to M6.Lubrication, sealingThe bearings are lubricated by the oil splashed off fromthe imbalance weights. Additional guide plates improvelubricant supply to the bearings. Mineral oilswith EP additives and anti-corrosion additives haveproved to be suitable.Internal sealing is provided by shaft seals, external sealingby O-ring seals.FAG 128


91: Vibrating road roller129 FAG


92 Double toggle jaw crusherDouble toggle jaw crushers have a large mouth opening.They are used, for example, as primary crushers toprepare ballast for road building. The coarse crushingis followed by further crushing operations until an aggregateof the size and shape required, e.g. gravel orgrit, is obtained.Operating dataInput power 103 kW; speed of eccentric shaftn = 210 min –1 ; mouth opening 1,200 x 900 mm;eccentric radius 28 mm.Bearing selection, dimensioningSwing jawMachining tolerancesEccentric shaftPitmanThe pitman is fitted to the eccentric part of the horizontalshaft and actuates the swing jaw through a doubletoggle lever system. The inner bearings supportingthe pitman must accommodate heavy crushing loads.The outer bearings transmit, in addition to theseloads, the flywheel weight and the circumferentialloads resulting from the drive. Due to the high loadingand the rugged operation, spherical roller bearings arechosen. Spherical roller bearings FAG 23260K.MB aremounted as outer bearings and FAG 23176K.MB asinner bearings. The pitman bearing arrangement is ofthe floating bearing type. The outer bearing arrangementfeatures a locating bearing at the drive side andthe floating bearing at the opposite side. With an indexof dynamic stressing f L ≈ 4.5 the bearing arrangement issafely dimensioned with regard to nominal rating life.The bearings are mounted on the shaft with adaptersleeves FAG H3260HGJ and FAG H3176HGJ, respectively.The bearing seats on the shaft are machinedto h7 with a cylindricity tolerance IT5/2 (DIN ISO1101), and the bores of housing and pitman to H7.Lubrication, sealingGrease lubrication with a lithium soap base grease ofpenetration class 2 wit EP additives (FAG rolling bearinggrease Arcanol L186V). The relubrication intervalfor the bearings is 2...3 months.The bearings are sealed by multiple labyrinths. Once ortwice a week, fresh grease is injected into the labyrinths.Locating bearingFloating bearing92: Bearing mounting of a double-toggle jaw crusherFAG 130


93 Hammer millHammer mills are mainly used for crushing ores, coal,and stone.Operating dataHourly throughput 90...120 t of iron ore; input power280 kW; rotor speed 1,480 min –1 , rotor weight includinghammers approximately 40 kN; bearing centre distance2,000 mm.Bearing selectionDue to the high loads and rugged operation, hammermill rotors are mounted on spherical roller bearings.This self-aligning bearing type can compensate for misalignmentsof the two plummer block housings, andpossible rotor deflections. Two spherical roller bearingsFAG 23228EASK.M.C3 are mounted, one acting asthe locating bearing, the other one as floating bearing.The increased radial clearance C3 was selected becauseof the high speed. The bearing inner rings heat upmore than the outer rings, causing the bearing clearanceto be reduced during operation.Bearing dimensioningThe rotor weight imposes a radial load on the bearings.Added to this are unbalanced loads and shock loadswhose magnitude can only be estimated. These loadsare introduced in the nominal rating life calculation bymultiplying the rotor weight G R with a supplementaryfactor f z of 2.5...3, depending on the operating conditions.The thrust loads acting on the bearings are sosmall they need not be taken into account in the lifecalculation.With the dynamic load rating C = 915 kN, the speedfactor f n = 0.32 (n = 1,480 min –1 ) and the rotor weightG R = 40 kN, the index of dynamic stressing f L for onebearing:f L = C · f n / (0.5 · G R · f z ) = 915 · 0.32 / (20 · 3) = 4.88An f L value of 3.5...4.5 is usually applied to hammermills. Thus the bearings are adequately dimensionedwith regard to nominal rating life (L h approximately100,000 h).Bearing mountingThe bearings are mounted on the rotor shaft withwithdrawal sleeves FAG AHX3228. They are fittedinto plummer block housings MGO3228K. Bothhousings (open design) are available for locating bearings(design BF) and for floating bearings (design BL).The split housings of series MGO were especially developedfor mill applications. They are designed for oillubrication and feature particularly effective seals.Machining tolerancesFor mounting with sleeves, the shaft seats are machinedto h7, with a cylindricity tolerance IT5/2 (DIN ISO1101). The housing bores are machined to G6. Thusthe requirement that the outer ring of the floating bearingmust be displaceable within the housing is met.Lubrication, sealingFor reliable operation at high speeds, the bearings areoil bath lubricated. Grease-packed labyrinths preventthe ingress of foreign matter. To increase the sealingefficiency, grease is replenished frequently. Flingergrooves on the shaft, and oil collecting grooves in thehousing covers retain the oil within the housing.LocatingbearingFloatingbearing93: Hammer mill mounting131 FAG


94 Double-shaft hammer crusherDouble-shaft hammer crushers are a special type ofhammer crushers or hammer mills. They feature twocontra-rotating shafts to which the hammers are attached.This type is especially suitable for crushinglarge-sized material with a high hourly throughput andoptimum size reduction.Operating dataHourly thoughput 350...400 t of iron ore; input power2 x 220 kW; rotor speed 395 min –1 , rotor weight includinghammers 100 kN; bearing centre distance2,270 mm.Bearing selectionDue to the rugged operation, spherical roller bearingsare mounted which can compensate for misalignmentbetween the two plummer blocks and for shaft deflections.Bearing dimensioningIn addition to the loads resulting from the rotorweight, the bearings have to accommodate loads resultingfrom imbalances and shocks. They are takeninto account by multiplying the rotor weight G R bythe supplementary factor f z = 2.5. Small thrust loadsneed not be taken into account in the life calculation.The shaft diameter at the bearing locations determinesthe use of one spherical roller bearing FAG23234EASK.M at each side. For the moderate speedsof this application normal radial clearance CN is satisfactory.With the dynamic load rating C = 1,370 kN, the speedfactor f n = 0.476 (n = 395 min –1 ) and the rotor weightG R = 100 kN, the index of dynamic stressing f L per bearing:f L = C · f n /(0.5 · G R · f z ) = 1,370 · 0.476/(50 · 2.5) = 5.2With this f L value, which corresponds to a nominal ratinglife L h of approximately 120,000 hours, the bearingsare very adequately dimensioned.Bearing mountingThe bearings are mounted on the rotor shaft withwithdrawal sleeves FAG AH3234 and mounted inFAG plummer block housings BNM3234KR.132887.One of the plummer blocks is designed as the floatingbearing (closed on one side, design AL), the other oneas the locating bearing (continuous shaft, design BF).The unsplit housings of series BNM were developedespecially for hammer mills and crushers. They weredesigned for grease lubrication (grease valve) andfeature particularly effective seals.Machining tolerancesThe shaft seats are machined to h7, with a cylindricitytolerance IT5/2 (DIN ISO 1101).The housing bores are machined to H7; this allows theouter ring of the floating bearing to be axially displaced.Lubrication, sealingGrease lubrication with FAG rolling bearing greaseArcanol L71V is satisfactory for the speeds in thisexample. Relubrication is required at certain intervals.A grease valve protects the bearing against over-lubrication.Due to the adverse ambient conditions a doublepassagelabyrinth seal is provided. Frequent grease replenishmentto the labyrinths improves sealing efficiency.FAG 132


Floating bearingLocating bearing94: Double-shaft hammer crusher133 FAG


95 Ball tube millTube mills are mostly used in the metallurgical, miningand cement industries. The tube mill described isused in an Australian gold mine for grinding auriferousminerals (grain sizes 4...30 mm) into grit by meansof grinding bodies (balls). The grain size of the materialdepends on the number of balls and the quantity ofadded water. The grinding drum, which revolvesaround its horizontal axis, is lined with chilled-castiron plates. Charged with the grinding stock, it is veryheavy.Operating dataDrum: diameter 5,490 mm, length 8,700 mm; inputpower 3,850 kW; speed 13.56 min –1 ; drum mass whenloaded 400 t; maximum radial load per bearing F r =1,962 kN; maximum thrust load F a = 100 kN; bearingdistance 11,680 mm, throughput 250 t/h.The equivalent dynamic loadP = f z · F r + Y · F a = 2 · 1.5 · 1,962 + 4.5 · 100 =3,393 kNWith a dynamic load rating C = 12,900 kN the index ofdynamic stressing:f L = C/P · f n =12,900/3,393 · 1.31 = 4.98 (L h > 100,000 h).The bearings are very safely dimensioned with regardto nominal rating life.The bearings are mounted in split FAG plummerblock housings SZA48/1500HF (locating bearing) andSZA48/1500HL (floating bearing). The outer rings aretightly fitted into shell sleeves (e.g. made of grey-castiron) in the lower housing half. They facilitate compensationof axial length variations. The sliding effectis enhanced by grease injected into the shellsleeve/housing joint.Bearing selectionTrunnion bearingsAs the drum rotates, the bearings have to accommodate,in addition to the heavy weight, constant shocktypeloads caused by the grinding bodies. Both drumtrunnions are supported on spherical roller bearings ofseries 239, 248 or 249. The bearings compensate forstatic and dynamic misalignments that can be causedby misalignments of the bearing seats (large bearingdistance) or drum deflections. In this example, sphericalroller bearings with a tapered bore (K 1:30), FAG248/1500BK30MB are mounted both as the locatingbearing at the drive end and as the floating bearing atthe feed end. The bearings are mounted on the trunnionwith a wedge sleeve.Drive pinion bearingsThe drive pinion is supported on two spherical rollerbearings FAG 23276BK.MB with adapter sleeveFAG H3276HG, in plummer block housings withTaconite-seals FAG SD3276TST.Bearing dimensioningThe dimensioning of the drum bearings is based onhalf the weight of the loaded drum(400/2 · 9.81 = 1,962 kN).The shock loads are taken into account by a shock factorf z = 1.5. The required nominal rating life is100,000 h; this corresponds to an index of dynamicstressing f L = 4.9.Machining tolerancesThe circumferentially loaded inner rings are press-fittedon the trunnion. This is easily achieved by mountingthem hydraulically on wedge sleeves. The radial clearancereduction and the radial clearance of the mountedbearing have to be observed (see table in FAG catalogueWL 41 520, chapter on spherical roller bearings).The trunnions are machined to h9, with a cylindricitytolerance IT5/2 (DIN ISO 1101); the housing boresto H7.Lubrication, sealingGrease lubrication with a lithium soap base grease ofpenetration class 2 with EP additives, e. g. FAG rollingbearing grease Arcanol L186V. Continuous replenishment(approx. 5 g/h per bearing) ensures adequate lubrication.The bearings are sealed by multiple labyrinths. Due tothe extreme ambient conditions, the labyrinths arepreceded by dirt baffle plates and rubbing seals (Vrings).This combination is also referred to as Taconitesealing. The labyrinths are also continuously replenishedwith approx. 5 g/h per labyrinth.FAG 134


95: Ball tube mill mounting135 FAG


96 Support roller of a rotary kilnRotary kilns for cement production can extend over alength of 150 m or more. The support rollers arespaced at about 30 m intervals.Operating dataKiln outside diameter 4.4 m; support roller diameter1.6 m; support roller width 0.8 m; radial load persupport roller 2,400 kN; thrust load 700 kN. Speed5 min –1 ; mass of support roller and housing 13 t.Bearing selection, dimensioningFor such rotary kilns FAG offers complete assembliesconsisting of a twin housing SRL, the support rollerwith axle LRW, and the bearings. In this example thetwo support-roller bearings are mounted into splitplummer block housings with a common base (frame)made of grey-cast iron. Spherical roller bearings FAG24184B (dynamic load rating C = 6,200 kN) aremounted in a floating bearing arrangement, i. e. theshaft can be displaced relative to the housing by a definedaxial clearance.In addition to the radial loads, the spherical rollerbearings accommodate thrust loads resulting from displacementsof the rotary kiln.With an index of dynamic stressing f L = 4.9, correspondingto a nominal rating life L h = 100,000 h, the bearingsare adequately designed.Machining tolerancesShaft to n6 (circumferential load on inner ring); housingbore to H7.Lubrication, sealingGrease lubrication with a lithium soap base grease withEP additives (e. g. rolling bearing grease ArcanolL186V).At the roller side the bearings are sealed with felt stripsand grease-packed labyrinths.FAG 136


96: Support roller of a rotary kiln137 FAG


Vibrating machinesVibrating screens are used for conveying and gradingbulk material. They operate in mines, quarries, stonecrushing plants and foundries, in the foodstuff andchemical industries, and in many other preparationand processing plants.The main vibrating screen types are: two-bearingscreens with circle throw, two-bearing screens withstraight-line motion, and four-bearing screens.Vibrator motors and vibrating road rollers also comeunder the category of vibrating machines.Selection of bearing type and bearing designRolling bearings in vibrating screens are stressed byhigh, mostly shock-type loads. To compound matters,the bearings, while rotating about their own axis, performa circular, elliptical or linear vibrating motion.This results in high radial accelerations (up to 7 g)which additionally stress the bearings, and especiallythe cages. High operating speeds, usually with inaccuratelyaligned bearing locations, and pronounced shaftdeflections are additional requirements which are bestmet by spherical roller bearings.For these adverse operating conditions FAG sphericalroller bearings with reduced bore and outside diametertolerances and an increased radial clearance are used:The FAG standard design E.T41A is used for shaft diametersof 40...150 mm. The centrifugal forces of theunloaded rollers are accommodated by two pressedsteel,window-type cages and radially supported by acage guiding ring in the outer ring.Shafts with diameters of 160 mm and more are supportedon vibrating screen bearings A.MA.T41A.These bearings have a fixed centre lip on the inner ringand retaining lips on both sides. The split machinedbrass cage is of the outer-ring riding type.Bearing dimensioningVibrating screen bearings which are comparable withfield-proven bearings can be dimensioned on the basisof the index of dynamic stressing f L , provided that theboundary conditions are comparable as well. f L valuesbetween 2.5 and 3 are ideal.FAG 138


97 Two-bearing screen with circle throwOperating dataScreen box weight G = 35 kN; vibration radius r =0.003 m; speed n = 1,200 min –1 ; number of bearingsz = 2 ; acceleration due to gravity g = 9.81 m/s 2 .Bearing dimensioningTwo-bearing screens work beyond the critical speed;thus the common centroidal axis of the screen box andthe unbalanced load does not change during rotation.The bearing load due to the screen box centrifugalforce is:F r = 1/z · G / g · r · (π · n/30) 2 == 1/2 · 35 / 9.81 · 0.003 · (3.14 · 1,200/30) 2 = 84.5 kNTo allow for the unfavourable dynamic stressing, thebearing load should be multiplied by the supplementaryfactor f z = 1.2. Thus, the equivalent dynamic loadP = f z · F r = 1.2 · 84.5 = 101.4 kNWith the index of dynamic stressing f L = 2.72 (L h =14,000 h) and the speed factor f n = 0.34 (n =1,200 min –1 ) the required dynamic load ratingC = f L /f n · P = 2.72/0.34 · 101.4 = 811.2 kN2The recommended index of dynamic stressing f L forvibrating screens is 2.5...3, corresponding to a nominalfatigue life L h of 11,000 to 20,000 hours. Sphericalroller bearings FAG 22324E.T41A with a dynamicload rating of 900 kN are chosen.Machining tolerancesThe eccentric shaft features two spherical roller bearings,one as the locating bearing, the other as floatingbearing. The inner rings are point loaded and mountedwith a shaft tolerance of g6 or f6. The outer rings arecircumferentially loaded and fitted tightly in the housingbore to P6.Lubrication, sealingCirculating oil lubrication. Mineral oils with a minimumviscosity of 20 mm 2 /s at operating temperatureare recommended. The oil should contain EP additivesand anti-corrosion additives.Outer sealing is provided by a grease-filled, replenishablelabyrinth. A flinger ring with an oil collectinggroove prevents oil leakage. A V-ring is providedbetween flinger ring and labyrinth to separate oil andgrease.1Floating bearing1 FestlagerL l97: Two-bearing screen with circle throwLocating bearing139 FAG


98 Two-bearing screen with straight-line motionBasically, a two-bearing screen with straight-linemotion consists of two contra-rotating, synchronouscircular throw systems.Operating dataScreen box weight G = 33 kN; imbalance weight G 1 =7.5 kN; amplitude r = 0.008 m; speed n = 900 min –1 ;number of bearings z = 4 ; acceleration due to gravityg = 9.81 m/s 2 .Bearing dimensioningThe bearing loads of a linear motion screen vary twicebetween the maximum value F rmax and the minimumvalue F rmin during one revolution of the eccentricshafts.For calculation of these loads, the distance R betweenthe centres of gravity of imbalance weight and the pertinentbearing axes is required. Weights G and G 1 , amplitudeof linear vibration r and distance R have thefollowing relationship:G · r = G 1 · (R – r)In this example R = 0.043 mWhen the centrifugal forces act perpendicular to thedirection of vibration, the maximum radial load F rmaxis calculated as follows:F rmax = 1/z · G 1 / g · R · (π · n/30) 2 == 1/4 · 7.5 / 9.81 · 0.043 · (3.14 · 900/30) 2 = 73 kNThe radial load is at its minimum (F rmin ) when thedirections of centrifugal forces and vibration coincide.The radial load is thenF rmin = 1/4 · G 1 /g · (R - r) · (π · n/30) 2 == 1/4 · 7.5/9.81 · 0.035 · (3.14 · 900/30) 2 = 59.4 kNSince the radial load varies between the maximum andminimum according to a sinusoidal pattern, theequivalent dynamic load P with the supplementaryfactor f z = 1.2 is thus:P = 1.2 · (0.68 · F rmax + 0.32 · F rmin ) == 1.2 · (0.68 · 73 + 0.32 · 59.4) = 82.4 kNWith the index of dynamic stressing f L = 2.53 (L h =11,000 h) selected for vibrating screens and the speedfactor f n = 0.372 (n = 900 min –1 ) the required dynamicload ratingC = f L /f n · P = 2.53/0.372 · 82.4 = 560.4 kNThe spherical roller bearing FAG 22320E.T41A with adynamic load rating of 655 kN is chosen.Machining tolerancesThe locating bearings of the two eccentric shafts are atthe gear end, the floating bearings at the drive end. Theinner rings (point load ) are have loose fits, i. e. theshaft is machined to g6 or f6. The outer rings are circumferentiallyloaded and tightly fitted in the housingbore (P6).Lubrication, sealingOil lubrication. For lubricating the spherical rollerbearings at the locating end, the oil thrown off by thegear suffices. A flinger ring is provided for this purposeat the opposite end. Baffle plates (A) at the housingfaces maintain an oil level reaching about the centrepoint of the lowest rollers. The oil level is such that thelower gear and the flinger ring are partly submerged.The oil level can be checked with a sight glass.A flinger ring and a V-ring in the labyrinth providesealing at the drive shaft passage.FAG 140


1 2AAB1 Locating bearing2 Floating bearingA Baffle platesB Sight glass98: Bearing mounting of a two-bearing screen with straight-line motion141 FAG


99 Four-bearing screenThe vibration radius of a four-bearing screen is a functionof the shaft eccentricity. It is not variable; thereforethese screens are also called rigid screens.Operating dataScreen box weight G = 60 kN; eccentric radius r =0.005 m; speed n = 850 min-1; number of inner bearingsz = 2; acceleration due to gravity g = 9.81 m/s 2 .Bearing dimensioningInner bearingsFor the two inner bearings of a four-bearing screen,which are subjected to vibration, the equivalent dynamicload P is the same as for the two-bearing screenwith circular throwP = 1.2 · F r = 1.2/z · G/g · r · (π · n/30) 2 == 1.2/2 · 60/9.81 · 0.005 · (3.14 · 850/30) 2 = 145.4 kNThe required dynamic load ratingC = f L /f n · P = 2.93/0.378 · 145.4 = 1,127 kNSpherical roller bearings FAG 22328E.T41A (dynamicload rating C = 1,220 kN) are chosen.Outer bearingsThe stationary outer bearings are only lightly loadedsince the centrifugal forces of the screen box are balancedby counterweights. Generally spherical rollerbearings of series 223 are also used. The bearing size isdictated by the shaft diameter so that the load carryingcapacity is high and fatigue life calculation unnecessary.Since these bearings are not subjected to vibration, thestandard design with normal clearance is satisfactory.In the example shown spherical roller bearings FAG22320EK (dynamic load rating C = 655 kN) arechosen.Machining tolerancesInner bearingsThe inner bearings (a locating-floating bearing arrangement) feature point load on the inner rings: The shaftis machined to g6 or f6. The bearings are fitted tightlyinto the housing (P6).Outer bearingsThe outer bearings – also a locating-floating bearingarrangement – are mounted on the shaft with withdrawalsleeves. The shaft is machined to h8, the housingbore to H7.Lubrication, sealingGrease lubrication with a lithium soap base grease ofpenetration class 2 with anti-corrosion and extremepressure additives. Grease supply between the rollerrows through lubricating holes in the outer rings.Sealing is provided by grease-packed, relubricatablelabyrinths.Locating bearingFloating bearingCounterweight99: Four-bearing screenFAG 142


100 Vibrator motorThe vibrations of vibrating equipment are generatedby one or several activators. An electric motor with animbalance rotor is an example of such an activator. It isreferred to as a "vibrator motor". Vibrator motors areprimarily mounted in machinery for making prefabricatedconcrete parts, in vibrating screens and vibratingchutes.Operating dataInput power N = 0.7 kW, speed n = 3,000 min –1 .The bearings are loaded by the rotor weight and thecentrifugal forces resulting from the imbalances: maximumradial load on one bearing F r = 6.5 kN.Bearing selection, dimensioningDue to the high centrifugal forces, the load carryingcapacity of the deep groove ball bearings usually usedfor medium-sized electric motors is not sufficient forthis application. Vibrator motors are, therefore, supportedon cylindrical roller bearings. The arrangementshown incorporates two cylindrical roller bearingsFAG NJ2306E.TVP2.C4; the dynamic load rating ofthe bearings is 73.5 kN.The adverse dynamic bearing stressing by the centrifugalforces is taken into account by a supplementaryfactor f z = 1.2. Considering this supplementary factor,the equivalent dynamic loadP = 1.2 · F r = 7.8 kN.With the speed factor f n = 0.26 (n = 3,000 min –1 ), theindex of dynamic stressingf L = C/P · f n = 73.5/7.8 · 0.26 = 2.45This f L value corresponds to a nominal rating life of10,000 h. Thus the bearings are correctly dimensioned.Machining tolerancesShaft to k5; housing to N6.The bearing outer rings carry circumferential load andare, therefore, tight fits. Since the inner rings are subjectedto oscillating loads, it is advisable to fit themtightly onto the shaft as well. With non-separable bearingsthis requirement would make bearing mountingand dismounting extremely complicated. Therefore,separable cylindrical roller bearings of design NJ areused.Bearing clearanceThe initial radial clearance of the bearings is reducedby tight fits. Further radial clearance reduction resultsfrom the different thermal expansion of inner andouter rings in operation. Therefore, bearings of radialclearance group C4 (i. e. radial clearance larger thanC3) are mounted.To prevent detrimental axial preloading, the innerrings are assembled so that an axial clearance of0.2...0.3 mm exists between the roller sets of the twobearings and the lips (floating bearing arrangement ).Lubrication, sealingBoth bearings are lubricated with grease. Lithium soapbase greases of penetration class 2 with EP additiveshave proved successful. Relubrication after approximately500 hours.Since the vibrator motor is closed at both ends, gaptypeseals with grooves are satisfactory.100: Imbalance rotor bearings of a vibrator motor143 FAG


101–103 Large capacity convertersConverters perform swinging motions and are occcasionallyrotated up to 360˚. Bearing selection is, therefore,based on static load carrying capacity. Importantcriteria in bearing selection are, besides a high staticload rating, the compensation of major misalignmentsand length variations. Misalignment invariably resultsfrom the large distance between the bearings and fromtrunnion ring distortion and deflection. The considerablelength variations are due to the large differences inconverter temperature as the converter is heated upand cools down.Bearing selectionExample 101 – showing the conventional design – featuresone spherical roller bearing each as locating bearingand as floating bearing. The housing of the floatingbearing is fitted with a sleeve. This simplifies axial displacementof the spherical roller bearing. To minimizethe frictional resistance, the bore of the sleeve isground and coated with dry lubricant (molybdenumdisulphide).For thrust load calculation a coefficient of friction ofµ = 0.1...0.15 is used.Example 102 shows two spherical roller bearingsmounted in the housings as locating bearings. Axial displacementis permitted by two collaterally arrangedlinear bearings (rollers) which provide support for oneof the two housings. With this design the amount offriction to be overcome during axial displacement islimited to the rolling contact friction occurring in thelinear bearings (coefficient of friction µ ≈ 0.05).Bearing dimensioningFor converters, the index of static stressing f s = C 0 /P 0should be more than 2; see calculation example.C 0 = static load rating of the bearingP 0 = equivalent static loadTwo spherical roller bearings FAG 230/900K.MB(static load rating C 0 = 26,000 kN, thrust factorY 0 = 3.1) are mounted.Locating bearingP 0 = F rF + Y 0 · (F a + 0.05 · F rL )= 5,800 + 3.1 · (800 + 265) = 9,100 kNIndex of static stressing f s = 26,000 / 9,100 = 2.85Floating bearingP 0 = F rL + Y 0 · 0.05 · F rL= 5,300 + 3.1 · 265 = 6,120 kNIndex of static stressing f s = 26,000 / 6,120 = 4.24Both bearings are thus safely dimensioned. Five cylindricalrollers (80 x 120 mm) each are required for thetwo linear bearings. The hardness of the guide rails(raceways) is 59...65 HRC.Machining tolerancesBearings with a cylindrical bore: trunnion to m6.Bearings with a tapered bore and hydraulic sleeve:trunnion to h7. The trunnions are machined with acylindricity tolerance IT5/2 (DIN ISO 1101).The support bores in the housing have H7 tolerance.Tighter fits should not be used in order to preventbearing ovality which might otherwise result from thesplit housing.Lubrication, sealingConverter bearings are lubricated with grease. Lithiumsoap base greases of penetration class 2 with EP andanti-corrosion additives (e. g. FAG rolling bearinggrease Arcanol L186V) are a good choice. Efficientsealing is achieved by graphited packing rings.Operating dataCalculation example: two spherical roller bearings andtwo linear bearings (example 102).Locating bearing: Radial load F rF = 5,800 kN;Floating bearing: Radial load F rL = 5,300 kN;Thrust load from drive F a = 800 kN and from axialdisplacement 0.05 · F rL = 265 kN;trunnion diameter at bearing seat 900 mm.Split rolling bearingsSteel mills often demand that the bearing at the converterdrive end are replaceable without dismountingthe drive unit. This requirement is satisfied by splitspherical roller bearings (example 103).For cost reasons, split bearings are usually used as replacementbearings.FAG 144


Locating bearingFloating bearing101: Converter bearings(two spherical roller bearings)Locating bearingFloating bearing102: Converter bearings(two spherical roller bearings,two linear bearings)103: Locating bearing end with splitspherical roller bearing145 FAG


104Roll bearings of afour-high cold rolling stand for aluminiumOperating dataBack-up rolls: roll diameter 1,525 mmroll body length 2,500 mmWork rolls: roll diameter 600 mmroll body length 2,500 mmMaximum rolling load 26,000 kNMaximum rolling speed 1,260 m/minSelection of the back-up roll bearings (fig. 104a)Radial bearingsThe high radial loads are best accommodated, in a limitedmounting space and at high speeds, by cylindricalroller bearings. One four-row cylindrical roller bearingFAG 527048 (dimensions 900 x 1,220 x 840 mm) ismounted at each roll end. The bearings feature pintypecages and reach a dynamic load rating of C =31,500 kN.The increased radial clearance C4 is required as the innerrings are fitted tightly and heat up more in operationthan the outer rings.Machining tolerances:Roll neck +0.350 / +0.440 mm, chock to H7.Thrust bearingsSince thrust loads in strip rolling stands are low, thrustbearings are used that are small compared to the radialbearings. The back-up roll is supported at both ends bya double-row tapered roller bearing FAG 531295A (dimensions400 x 650 x 240 mm) with a dynamic loadrating C of 3,450 kN.Machining tolerances: Shaft to f6.The cups are not supported radially; axially, they areadjusted by means of helical springs.104a: Back-up roll mounting of a four-high cold rolling stand for aluminium (identical bearing arrangements at drive end and operating end)FAG 146


Selection of the work roll bearings (figs. 104b, c)Radial bearingsEach roll end is supported on two double-row cylindricalroller bearings FAG 532381.K22 (dimensions350 x 500 x 190 mm). The bearings feature reducedtolerances so that all roller rows are evenly loaded,machined brass cages and an increased radial clearanceC3.Machining tolerancesRoll neck to p6; chock bore to H6.Thrust bearingsLocating bearing end (operating end): two angular contactball bearings FAG 7064MP.UA in X arrangement.Any two bearings of universal design UA can bematched in X or O arrangement, yielding a bearing pairwith a narrow axial clearance. The angular contact ballbearings accommodate the thrust loads from the rolls.Floating bearing end (drive end): a deep groove ballbearing FAG 61972M.C3 merely provides axial guidancefor the chock.Machining tolerances: Sleeve to k6; outer rings not radiallysupported.LubricationAll bearings supporting the back-up rolls and workrolls are oil-mist lubricated. A high-viscosity oil with EPadditives is used as the cylindrical roller bearings – especiallyat the back-up rolls – are heavily loaded andhave to accommodate operating temperatures of up to70 ˚C.104b: Work roll bearings, operating end104c: Work roll bearings, drive end147 FAG


Work rolls for the finishing section of a105 four-high hot wide strip millWork roll bearings are often exposed to large amountsof water or roll coolant. In addition, considerableamounts of dirt have to be accommodated in hot rollingmills. Therefore, the bearings must be efficientlysealed. As a rule, they are lubricated with grease, whichimproves sealing efficiency. Operators of modern rollingmills endeavour to reduce grease consumption anddamage to the environment caused by escaping greasewateremulsion.Operating dataRoll body diameter 736 mm; roll body length2,235 mm; rolling speed 3.5...15 m/s.Bearing selection, dimensioningFour-row tapered roller bearings have proved to be agood choice for work rolls. They accommodate notonly high radial loads but also thrust loads, and theyrequire only little mounting space. The bearings have asliding fit on the roll neck, allowing rapid roll changes.In the example shown, sealed four-row tapered rollerbearings FAG 563681A (dimensions 482.6 x 615.95x 330.2 mm) are used.The service life of work roll bearings is mainly dictatedby the loads, rolling speed, lubrication and cleanliness.Open bearings, as a rule, do not reach their nominalrating life due to adverse lubricating and cleanlinessconditions. On the other hand, the modified life calculationfor sealed bearings usually yields a 23 factors > 1,i. e. the attainable life exceeds the nominal rating life.In spite of the lower load rating, the value is generallyhigher than that reached by an open bearing of thesame size.Lubrication, sealingThe bearings are filled with relatively small amounts ofhigh-quality rolling bearing grease. On each side theyfeature a double-lip rubbing seal. The inner lip preventsgrease escape from the bearing; the outer lip protectsthe bearing from moisture that might have penetratedinto the chock. No relubrication is required duringrolling operation and roll change. The amount ofgrease provided during assembly usually suffices for theduration of one chock regrinding cycle, i. e. for1,000...1,200 hours of operation. The chocks are fittedwith the conventional external seals (collar seals).These are filled with a moderately priced, environmentallycompatible sealing grease.105: Work roll mounting for the finishing section of a four-high hot wide strip millFAG 148


Roll mountings of a two-high ingot slab stand106 or ingot billet standOperating dataRoll diameter 1,168 mm (46"); roll body length3,100 mm (122"); rolling speed 2.5...5 m/s; yearlyoutput of 1 million tons. The mill operates as a reversingstand, i.e. the rolled material moves back andforth, and the sense of rotation of the rolls alternatesfrom pass to pass.The bearing rings are loosely fitted on the roll neckand in the chocks for easy mounting and dismounting.The cones creep on the roll neck in circumferential direction.To reduce wear and heat generation, the fittingsurfaces are usually supplied with grease through a helicalgroove in the bearing bore.Roll bearingsThe work rolls in this example are also supported onmulti-row tapered roller bearings. These bearings requirerelatively little mounting space and accommodatehigh radial and thrust loads. The rolls are supportedat each end on a four-row tapered roller bearingFAG 514433A (dimensions 730.25 x 1,035.05x 755.65 mm).LubricationThe tapered roller bearings are lubricated with greasewhich is continually supplied through grooves in thefaces of cone and spacer ring.Excess grease escapes through the bores in the centralcup and in the spacers.106: Roll mounting of a two-high ingot slab stand or ingot billet stand149 FAG


107 Combined reduction and cogging wheel gear of a billet millOperating dataThe billet mill is designed for a monthly output of55,000 tons. The mill comprises a roughing and a finishingsection, each with two vertical and two horizontalstands in alternate arrangement. The drive of thevertical stands is on top; with this arrangement thefoundations are not as deep as for a bottom drive; onthe other hand, the top drive involves a greater overallheight.Rated horsepower 1,100/2,200 kW;motor speed 350/750 min –1 .Compared to two angular contact ball bearings, a fourpoint bearing offers the advantage of smaller widthand, compared to a deep groove ball bearing, the advantageof smaller axial clearance and higher thrust carryingcapacity. The use of four point bearings is, however,limited to applications where the thrust load isnot constantly reversing. The bevel gear shafts featurethe smallest possible axial clearance to ensure perfectmeshing of the spiral-toothed gears. This is achievedby one duplex pair of angular contact ball bearingseach on the pinion shaft and on the bevel shaft. Theyalso accommodate the thrust load whereas the radialload is taken up by cylindrical roller bearings.Machining tolerancesBearing selection, dimensioningRadial loads and thrust loads are accommodated separately:the radial loads by cylindrical roller bearings, thethrust loads by angular contact ball bearings and fourpoint bearings. Cylindrical roller bearings offer thebest radial load carrying capacity in a limited mountingspace, thus keeping the distance between the gearshafts to a minimum. One decisive factor in the selectionof the bearing size is the diameter of the individualgear shafts determined in the strength calculation.The two largest cylindrical roller bearings of the gearare situated on the cogging wheel side and have thefollowing dimensions: 750 x 1,000 x 250 mm. Axiallocation of the four gear shafts is provided by one fourpoint bearing each which are double direction angularcontact ball bearings.Cylindrical roller bearings: Shaft to p6; housing toH6/H7.Four point bearings and angular contact ball bearings:Shaft to f6; housing to D10.The outer rings of the four point bearings and angularcontact ball bearings are fitted into the housing withclearance to relieve them of radial loads; thus, they accommodateonly thrust loads.LubricationCirculating oil lubrication. The bearings and gearsshare the same lubrication system. The oil is directlysupplied to the bearings via an oil filter which preventscontamination of the bearings by particles abradedfrom the gears.FAG 150


107: Combined reduction and cogging wheel gear of a billet mill151 FAG


108 Work rolls of a section millThe roll stand frames expand under the influence ofhigh rolling loads, which can have a negative effect onthe quality of the rolled material. This is usually preventedby means of elaborate roll adjustment mechanisms.Another way to compensate for the negativeeffect of the material's elasticity is to hydraulically preloadthe chocks which support the rolls and their bearingmountings against each other via the roll stands(see schematic drawing).9 of the 13 in-line stands of a section mill are fittedwith such hydraulically preloaded chocks. Five of thenine preloaded stands can also operate as universalstands. For this purpose they are equipped with twovertically arranged roll sets.Roll neck mountingsThe horizontal rolls are supported by multi-row cylindricalroller bearings and tapered roller bearings. Thecylindrical roller bearings at the drive end compensatefor the length variations caused by heat expansion.Compensation of length variations through the chockaxially floating in the stand at the drive end is not possiblewith preloaded chocks.The horizontal rolls in the roughing stands, which areloaded with 3,150 kN, are supported in four-row cylindricalroller bearings and four-row tapered rollerbearings of 355.6 x 257.2 x 323.8 mm (fig. a). Thebearings have a loose fit on the roll neck (e7), whichsimplifies mounting.No loose fit can be provided in those stands where sectionsteels are finish-rolled as the required quality canonly be achieved with accurately guided rolls. For thisreason cylindrical roller bearings and tapered rollerbearings with a tapered bore were selected and pressfittedonto the tapered roll neck. The hydraulic methodused simplifies mounting and dismounting. Due tothe lower rolling load (2,550 kN), the horizontal rollsin this case are supported by double-row cylindricalroller bearings and tapered roller bearings of 220.1x 336.6 x 244.5 mm (fig. b).The vertical rolls are each supported by a tapered rollerbearing pair (dimensions 165.1 x 336.6 x 194.2 mm)in O arrangement (fig. a). The bearings sit directly onthe rolls. As the rolling stock enters, the vertical rollsand their bearings are accelerated to operating speedvery quickly. The tapered roller bearings are preloadedto ensure that the rolling elements always maintain contactwith the raceways at these speeds. This is achievedby matching the tolerances of the bearings and bearingseats in such a way that the bearings after mountinghave the right preload without any fitting work.1 Hydraulic piston2 Upper chock3 Piston ram4 Lower chock5 FrameFAG 152


108a: Bearing mounting of horizontal rolls in the preloaded roughing standsand bearing mounting of the vertical rolls108b: Bearing mounting of horizontal rolls for stands in which section steel is finish-rolled153 FAG


Two-high rolls of a dressing stand109 for copper and brass bandsOn this dressing stand copper and brass bands withwidths between 500 and 1,050 mm are rolled. Themaximum initial thickness is 4 mm, and the minimumfinal thickness is 0.2 mm."Counterbending" is one special feature of this stand.The rolling forces cause an elastic deflection of therolls. This deflection is hydraulically compensated forby counterbending forces. The counterbending forcesare applied to the roll necks on both sides and outsidethe roll neck mounting via spherical roller bearings.This counterbending ensures a uniform band thicknessover the entire band width.Operating dataTwo-high roll diameter 690/650 mm; roll body length1,150 mm; maximum rolling speed 230 m/min; maximumrolling force 8,000 kN; maximum counterbendingforce 1,300 kN per roll neck.Counterbending bearingsThe counterbending forces are applied via sphericalroller bearings FAG 24068B.MB.Machining tolerances: roll neck to e7, housing to H6.Accommodation of radial loadsOne four-row cylindrical roller bearing FAG 547961(dimensions 445 x 600 x 435 mm) is mounted at eachend. The cylindrical roller bearings are fitted with pintypecages consisting of two side washers to which thepins passing through the rollers are fastened. Groovesin the inner ring faces facilitate dismounting.Machining tolerances:roll neck +0.160 / +0.200 mm, chock H6.Accommodation of thrust loadsAt the operating end the axial forces are accommodatedby two O arranged angular contact ball bearingsFAG 507227.N10BA (dimensions 400 x 600x 90 mm).At the drive end the chock is located on the roll neckby a deep groove ball bearing FAG 6080M.C3.Machining tolerances: roll neck to f6, outer ringradially relieved.LubricationThe cylindrical roller bearings, like the other bearings,are lubricated with a lithium soap base grease with EPadditives. They can easily be lubricated through lubricatingholes and lubricating grooves in the outer ringsand spacers.FAG 154


Drive endOperating endCounterbending bearingRoll bearings109: Two-high rolls of a dressing stand155 FAG


110 Straightening rolls of a rail straightenerRails for railway track systems or for craneways are hotrolled in rolling mills. After rolling the rails cool downon cooling beds but not uniformly, resulting in warping.Afterwards they have to be straightened in railstraighteners between horizontal and vertical rolls.The straightening plant consists of two machines oneinstalled behind the other. In the first machine the railsrun through horizontally arranged rolls, in the secondmachine through vertically arranged rolls. Thus therails are straightened in both planes after having passedthrough the two machines.Each machine features nine straightening rolls, four ofwhich are being driven. The straightening rolls withdiameters of 600...1,200 mm form an overhung arrangementin order to allow easy replacement.Demands on the bearing assemblyThe mounting space for the bearings is dictated by thedistance of the straightening rolls. In this mountingspace bearings are accommodated which have such ahigh load carrying capacity as to allow for reasonablerunning times.The bearing assembly for the straightening rolls musthave maximum rigidity since this determines the accuracyof the rolled stock.The roll position must be adjustable to the position ofthe rolled stock. For this reason the bearing assemblyhad to be designed such as to allow for a change of theposition of the straightening rolls by ±50 mm in theaxial direction.Horizontal straightening rollsThe maximum rolling force at the horizontal rolls is4,200 kN. Depending on the type of rolled stock,thrust loads of up to 2,000 kN have to be accommodated.Speeds range from two to 60 min –1 .Double-row cylindrical roller bearings have been providedto accommodate the radial forces and because oftheir high load carrying capacity. The higher loadedcylindrical roller bearing, which is situated directlybeside the roll, was especially developed for supportingthe straightening rolls (dimensions 530 x 780 x 285/475 mm). The less loaded cylindrical roller bearing hasthe dimensions 300 x 460 x 180 mm.The cylindrical roller bearings are fitted with boredrollers which are evenly spaced by pins and cage sidewashers.As this design allows the distance between the rollersto be indefinitely small, the largest possible number ofrollers can be fitted and, adapted to the mountingspace, the highest possible load carrying capacity canbe obtained for the bearing.The thrust loads are accommodated by two sphericalroller thrust bearings FAG 29448E.MB (dimensions240 x 440 x 122 mm). They are spring-adjusted.When positioning the straightening rolls, the bearingsmust be able to compensate for axial displacements byup to ±50 mm. This is made possible by providing anextended inner ring for the cylindrical roller bearinglocated beside the straightening roll. The inner ringwidth is such that the lips of the two seals always slidesafely on the inner ring even with maximum axial displacement.The second cylindrical roller bearing is seated, togetherwith the two spherical roller thrust bearings, in asleeve which is axially displaceable within the hollowcylinder. The position of the straightening rolls relativeto the rolled stock is adjusted by means of a ball screw.Vertical straightening rollsThe vertical straightening roll bearing arrangement isin principle identical to that of the horizontal straighteningrolls. Due to the lower straightening loads, however,smaller bearings can be mounted.Radial bearings: one axially displaceable double-rowcylindrical roller bearing (dimensions 340 x 520x 200/305 mm) and one single-row cylindrical rollerbearing FAG NU2244M.C3 (dimensions 220 x 400x 108 mm).Thrust bearings: two spherical roller thrust bearingsFAG 29432E (dimensions 160 x 320 x 95 mm).FAG 156


Lubrication, sealingIn spite of the high loads and the low speeds it wouldbe possible to lubricate the cylindrical roller bearingswith grease. However, the spherical roller thrust bearingsmust be oil-lubricated. Therefore, all bearings aresupplied with oil by means of a central lubricatingsystem. The oil flow rate per straightening roll unit isabout 10 l/min.At the spherical roller thrust bearing end the unit isclosed by a cover. At the shaft opening in the directionof the straightening roll two laterally reversed, greaselubricatedseal rings prevent oil escape and penetrationof contaminants into the bearings.110: Horizontal straightening rolls157 FAG


111 Disk ploughIn a disk plough the usual stationary blades are replacedby revolving disks fitted to the plough frame.The working width of the plough is determined by thenumber of disks.Bearing selectionDuring ploughing both radial and axial loads are imposedon the bearings. Bearing loads depend on soilconditions and cannot, therefore, be exactly determined.For safety reasons roller bearings with the maximumpossible load carrying capacity are used. Onetapered roller bearing FAG 30210A (T3DB050 *) andone FAG 30306A (T2FB030 *) are installed in Oarrangement and adjusted, via the cone of the smallerbearing, with zero clearance. This cone must, therefore,be able to slide on the journal.Machining toleranceson the journal:– j6 for the smaller bearing,– k6 for the larger bearing;in the housing: N7.Lubrication, sealingGrease lubrication (FAG rolling bearing grease ArcanolL186V). The bearings are adequately protected fromdirt and atmospheric influences by means spring steelseals and an additional labyrinth seal.*) Designation to DIN ISO 355FAG 158


111: Disk plough159 FAG


112 Plane sifterSifters are used in flour mills to segregate the differentconstituents (e.g. groats, grits, flour). The plane sifterdescribed in this example consists of four sections,each comprising 12 sieves fastened to a frame. Aneccentric shaft induces circular vibrations in the framesieveassembly.Operating dataStarting power 1.1 kW, operating power 0.22 kW;speed 220...230 min –1 ; total weight of balancingmasses 5.5 kN; distance between centre of gravity ofbalancing masses and axis of rotation 250 mm; totalweight of frame and sieves plus material to be sifted20...25 kN.Bearing selectionThe drive shaft with the balancing masses is suspendedfrom the top bearing. The supporting bearing must beself-aligning in order to avoid preloading. The bearingsmounted are a self-aligning ball bearing FAG 1213(65 x 120 x 23 mm) and a thrust ball bearing FAG53214 (70 x 105 x 28,8 mm). The spherical housingwasher FAG U214 compensates for misalignmentduring mounting.The thrust bearing has to accommodate the weight ofthe drive shaft and balancing masses. The eccentricshaft of the sifter frame is supported by a spherical rollerbearing FAG 22320E.T41A. This bearing accommodatesthe high centrifugal forces resulting from thecircular throw of the sifter frame and sieves. Sleeve B isa loose fit on the eccentric shaft; thus the sphericalroller bearing is axially displaceable together with thesleeve and cannot be submitted to detrimental axialpreloading.Machining tolerances– Self-aligning ball bearing.Hollow shaft to k6, pulley bore to J6.– Spherical roller bearing.Sleeve to k6, frame housing bore to K6.LubricationThe ball bearings at the top mounting run in an oilbath. The spherical roller bearing at the bottommounting is lubricated by circulating oil. A thread cutin the eccentric shaft feeds the oil upward throughsleeve B. From the top the oil passes through thespherical roller bearing and back into the oil bath.Layout of a plane sifterFAG 160


Pulley12112: Plane sifter161 FAG


Printing pressesPrinting quality is created in the heart of a printingpress, the printing group with its main cylinders. Platecylinders, blanket cylinders and impression cylindersare, therefore, guided in rolling bearings which are particularlylow in friction and which have a high degreeof running accuracy and radial rigidity.FAG has designed a number of highly efficient locating/floatingbearing arrangements for the main cylinderbearings ranging from solutions with cylindrical rollerbearings, tapered roller bearing pairs and spherical rollerbearings to triple-ring eccentric bearing units.113 Impression cylinders of a newspaper rotary printing pressDepending on the specific application, a variety of solutionscan be adopted for supporting impression cylindersin a newspaper rotary printing press. Often thefloating bearing at the operating end is a cylindricalroller bearing and the locating bearing arrangement atthe drive end consists of a spherical roller bearing or atapered roller bearing pair. The floating bearing accommodatesonly radial loads whereas the locating bearingtakes up both radial and thrust loads. Differing springrates (elastic deformation of rolling elements and raceways)and loads acting on the bearings can result in adiffering vibration behaviour at each end of the cylinders(negative effect on printing quality).Operating dataThe forces acting on impression cylinders in rotaryprinting presses are safely accommodated by FAG rollingbearings. In newspaper rotary printing presses apaper web, which may be up to 1,400 mm wide, is fedinto the machine via automatic wheel stands at a speedof 9.81 m/s. At a maximum speed of the impressioncylinders of 35,000 revolutions per hour and doubleproduction, the rotary printing press produces 7,000copies per hour with a volume of up to 80 pages.The circumference and width of the impression cylindersare adapted to the required newspaper sizes (e.g.cylinder diameter 325 mm, speed 583.3 min –1 , mass1,100 kg, operating temperature 50...60 °C, averagetime in operation 7,000 hours per year).Bearing selectionTo rule out differences in vibration behaviour FAG hasseparated the accommodation of the radial and axialloads from the impression cylinders.At each end the radial loads are accommodated by adouble-row cylindrical roller bearing FAGNN3024ASK.M.SP. A deep groove ball bearing pair2 x FAG 16024.C3 provides axial guidance for the impressioncylinder. The outer rings are radially relievedso that the ball bearings exclusively accommodate axialguiding forces in both directions. By providing identicalbearing arrangements on both sides of the impressioncylinder identical spring rates are obtained.The separation of radial and thrust loads means thatthe radially supporting bearings are symmetricallyloaded. This produces a uniform vibration behaviouron both sides of the impression cylinder.Bearing clearance and adjustmentThe low-friction precision bearings are accommodatedon both sides by eccentric bushes which serve to controlthe "impression on" and "impression off" movementsof the different impression cylinders independentlyof each other. This requires a high guiding accuracyand a minimal radial clearance. Heat developmentwithin the bearing is low, which helps achieve the requiredoptimal guiding accuracy. The bearing clearanceof 0...10 µm is adjusted via the tapered bearingseat. The temperature-related length compensationtakes place in the cylindrical roller bearings betweenthe rollers and the outer ring raceway so that the outerring can be fitted tightly in spite of the point load.FAG 162


The deep groove ball bearings are fitted in X arrangementwith zero clearance (Technical SpecificationN13CA). The C3 radial clearance ensures a contactangle which is favourable for accommodating the axialguiding forces.Machining tolerancesCylindrical roller bearingsInner ring: Circumferential load; interference fit ontapered shaft 1:12.Outer ring: Point load; housing bore to K6.Deep groove ball bearingsShaft to j6 (k6),outer ring radially relieved in the housing.Lubrication, sealingThe bearings are automatically supplied with lubricant.Through a circumferential groove and lubricatingholes in the outer ring the lubricant is fed directlyinto the bearings. At the operator end the supply linesare usually connected to a central grease lubricationsystem. V-ring seals prevent both grease escape and dirtingresss. The bearings at the drive end are suppliedwith oil from the transmission oil lubrication systemvia feed ducts. The oil first flows through the cylindricalroller bearing and then through the deep grooveball bearing pair. At the cylinder end a pressurerelievedshaft seal retains the oil in the lubricatingsystem.113: Impression cylinder of a KBA Commander newspaper rotary printing press163 FAG


114 Blanket cylinder of a sheet-fed offset pressTo date it was common practice to integrate cylindricalroller bearings, needle roller bearings or other designsin a sliding bearing supported sleeve and to accuratelyfit this complete unit into an opening in the sidewallof the machine frame; this required an elaborate technologyand was costly. Both the considerable cost andthe risk of the sleeve getting jammed during the "impressionon" and "impression off" movements of theblanket cylinder are eliminated by using a new tripleringeccentric bearing unit. It offers the benefit of absolutezero clearance which is not possible with theconventional unit as the sleeve always requires someclearance. Another significant advantage is the adjustablepreload which allows its radial rigidity to be considerablyincreased compared to bearings with clearance.Lubrication, sealingThe eccentric units can be lubricated both with greaseand with oil. Thanks to the favourable ambient conditions,the lubricant is only very slightly stressed so thatlong grease relubrication intervals and thus a longservice life are possible. A non-rubbing gap-type sealprevents grease escape.With oil lubrication, the oil flows to the bearing rollersthrough feed ducts. Via collecting grooves and returnholes the oil returns to the oil circuit.Bearing arrangementThe FAG triple-ring eccentric bearing units (floatingbearings) are available both with a cylindrical and witha tapered bore. The ready-to-mount unit is based onan NN cylindrical roller bearing design which is usedas a low-friction precision bearing in machine tools, anda double-row needle roller bearing which guides theeccentric ring. Axial guidance of the cylinder is providedby angular contact ball bearings (FAG 7207B) in Xarrangement, or by a thrust ball bearing.Operating dataRoll weight; press-on force; nominal speedBearing dimensioningAn index of dynamic stressing f L of 4...4.5 would beideal. This corresponds to a nominal life L h of 50,000 –80,000 hours. Under the given conditions the bearingsare adequately dimensioned so that an adjusted ratinglife calculation is not required.Machining tolerancesThe inner rings are subjected to circumferential load. Atight fit is obtained by machining the cylinder journalto k4 (k5). With a tapered bearing seat, an interferencefit is also obtained by axial displacement.The outer ring is mounted with a K5 or K6 fit or reducedtolerances (with a slight interference).114: Triple ring bearing for a blanket cylinderFAG 164


115 Centrifugal pumpOperating dataInput power 44 kW; delivery rate 24,000 l/min;delivery head 9 m; speed n = 1,450 min –1 ; axial thrust7.7 kN.Bearing selection, dimensioningThe impeller is overhung. The coupling end of the impellershaft is fitted with a duplex pair of contact ballbearings FAG 7314B.TVP.UA mounted in X arrangement.The suffix UA identifies bearings which can beuniversally mounted in tandem, O and X arrangement.When mounted in O or X arrangement, if the shaft ismachined to j5 and the housing to J6, the bearingshave a slight axial clearance. The bearing pair acts asthe locating bearing and accommodates the thrustF a = 7.7 kN. The radial load F r is approx. 5.9 kN.Since F a /F r = 1.3 > e = 1.14, the equivalent dynamicload P of the bearing pairP = 0.57 · F r + 0.93 · F a = 10.5 kNThus the index of dynamic stressingf L = C/P · f n = 186/10.5 · 0.284 = 5.03The nominal life amounts to approximately 60,000hours. The speed factor for ball bearings f n = 0.284(n = 1,450 min –1 ) and the dynamic load rating of thebearing pairC = 1.625 · C individual bearing = 1.625 · 114 = 186 kN.The impeller end of the shaft is fitted with a cylindricalroller bearing FAG NU314E.TVP2 acting as thefloating bearing. This bearing supports a radial load ofapproximately 11 kN. Thus, the index of dynamicstressingf L = C/P · f n = 204/11 · 0.322 = 5.97corresponding to a nominal rating life of more than100,000 hours.With the speed factor for roller bearings f n = 0.322(n = 1,450 min –1 ), the dynamic load rating of the bearingC = 204 kN.The recommended f L values for centrifugal pumps are3 to 4.5. The bearings are, therefore, adequately dimensionedwith regard to fatigue life. The service life isshorter if formation of condensation water in the bearingsor penetration of contaminants is expected.Lubrication, sealingOil bath lubrication. The oil level should be no higherthan the centre point of the lowest rolling element. Thebearings are sealed by shaft seals. At the impeller end ofthe shaft a labyrinth provides extra sealing protection.Locating bearingFloating bearing115: Centrifugal pump165 FAG


116 Axial piston machineCylinder block A accommodates a number of pistonsB symmetrically arranged about the rotational axis.Piston rods C transmit the rotation of drive shaft D tothe cylinder block. They also produce the reciprocatingmotion of the pistons, provided that the rotationalaxis of cylinder block and drive shaft are at an angle toeach other.Fluid intake and discharge are controlled via two kidney-shapedopenings E in pump housing F. Bore G establishesconnection from each cylinder to openings E.During one rotation of the cylinder block, each boresweeps once over the intake (suction) and discharge(pressure) openings. The discharge opening is subjectedto high pressure. Consequently, the pistons are actedupon by a force. This force is carried by the pistonrods to the drive shaft and from there to the drive shaftbearings.D C B A GFEBearing selectionAt relatively high speeds, bearings H and J have toaccommodate the reactions from the calculated resultantload. The bearing mounting should be simple andcompact.These requirements are met by deep groove ball bearingsand angular contact ball bearings. Bearing locationH features a deep groove ball bearing FAG 6208,bearing location J two universal angular contact ballbearings FAG 7209B.TVP.UA in tandem arrangement.Suffix UA indicates that the bearings can be universallymounted in tandem, O or X arrangement.HJIn axial piston machines only some of the pistons arepressurized (normally half of all pistons). The individualforces of the loaded pistons are combined to give aresultant load which acts eccentrically on the swashplate and/or drive flange.Operating dataRated pressure p = 100 bar = 10 N/mm 2 ; max. speedn max = 3,000 min –1 , operating speed n nom =1,800 min –1 ; piston diameter d K = 20 mm, pistonpitch circle = 59 mm, angle of inclination = 25°,number of pistons z = 7; distance between load lineand rotational axis e = 19.3 mm.eBearing dimensioningAssuming that half of the pistons are loaded, pistonloadF K = z/2 · p · d K2 . π/4 = 3.5 · 10 · 400 · 3.14/4 == 11,000 N = 11 kNFor determination of the bearing loads the piston loadF K is resolved into tangential component F Kt andthrust load component F Ka :F Kt = F K · sin = 11 · 0.4226 = 4.65 kNF Ka = F K · cos = 11 · 0.906 = 9.97 kNThe two components of the piston load produce radialloads normal to each other at the bearing locations.The following bearing loads can be calculated bymeans of the load diagram:Bearing location JF Jx = F Ka · e/l = 9.97 · 19.3/90 = 2.14 kNF Jy = F Kt · (l + t)/l = 4.65 · (90 + 10)/90 = 5.17 kNF rJ = √ F Jx2 + F Jy2 = √ 4.58 + 26.73 = 5.59 kNFAG 166


In addition to this radial load F rJ , bearing location Jaccommodates the thrust load component of the pistonload:F aJ = F Ka = 9.97 kNThus, the equivalent dynamic load with F a /F r =9.97/5.59 > e = 1.14 and X = 0.35 and Y = 0.57.P = 0.35 · F rJ + 0.57 · F aJ == 0.35 · 5.59 + 0.57 · 9.97 = 7.64 kNWith the dynamic load rating C = 72 kN and the speedfactor f n = 0.265 (n = 1,800 min –1 ) the index of dynamicstressingf L = C/P · f n = 72/7.64 · 0.265 = 2.5Here the load rating C of the bearing pair is taken asdouble the load rating of a single bearing.Bearing location HF Hx = F Ka · e/l = 9.97 · 19.3/90 = 2.14 kNF Hy = F Kt · t/l = 4.65 · 10/90 = 0.52 kNF rH = √ F Hx2 + F Hy2 = √ 4.58 + 0.27 = 2.2 kNThe equivalent dynamic load for the deep groove ballbearing equals the radial load:P = F rH = 2.2 kNWith the dynamic load rating C = 29 kN and the speedfactor f n = 0.265 (n = 1,800 min –1 ) the index of dynamicstressingf L = C/P · f n = 29/2.2 · 0.265 = 3.49The index f L for axial piston machines selected isbetween 1 and 2.5; thus the bearing mounting is adequatelydimensioned. Loads occurring with gearwheeldrive or V-belt drive are not taken into account in thisexample.Machining tolerancesSeat Deep groove Angular contactball bearing ball bearingShaft j5 k5Housing H6 J6116: Drive flange of an axial piston machine167 FAG


117 Axial piston machineOperating dataRated pressure p = 150 bar; maximum speedn max = 3,000 min –1 , operating speed n nom =1,500 min –1 ; piston diameter d K = 25 mm, pistonpitch circle = 73.5 mm; angle of inclination = 25°;number of pistons z = 7; distance between load lineand rotational axis e = 24 mm.To minimize shaft tilting due to the radial clearance ofthe deep groove ball bearing, Belleville spring washerskeep the bearing under light axial preload, thus ensuringzero clearance. A comparison of the f L values determinedfor the two pumps shows that the pump describedin example 117 is designed for only a shortoperating life (rating fatigue life 850 h). This life spanis, however, sufficient for many applications (e.g.dump trucks).Bearing selection, dimensioningThe bearing loads are determined as in example 116.Bearing location H: Deep groove ball bearingFAG 6311Index of dynamic stressing f L = 2.98Bearing location J: Angular contact ball bearingFAG 7311.TVPIndex of dynamic stressing f L = 1.19In examples 116 and 117 the axial load is accommodatedby angular contact ball bearings mounted nearthe drive flange end. Counter guidance is provided by adeep groove ball bearing.Lubrication, sealingThe bearings are lubricated by leakage oil from thepump. A shaft seal is satisfactory.Machining tolerancesSeat Deep groove Angular contactball bearing ball bearingShaft h6 j5Housing J6 J6117: Drive flange of an axial piston machineFAG 168


118 ExhausterThe exhauster is of the double-flow type; rotor weight22 kN; speed 1,200 min –1 ; exhaust gas temperatureapprox. 180 °C.Bearing selection, dimensioningThe use of plummer blocks for mounting the rotorshaft is simple and economical. The shaft diameter isdictated by strength considerations, and determinesplummer block and bearing size.The shaft is mounted on spherical roller bearings FAG22226E.C3 fitted in housings FAG LOE226BF andFAG LOE226AL. Due to the exhaust gas temperatureof +180 °C and the relatively high exhauster speed, thebearings feature an increased radial clearance C3. Thisprevents the bearings from running under preloadwhen there are major temperature differences betweeninner and outer ring. In addition, cooling discs are requiredto limit the bearing temperature. The plummerblock at the drive end is designed as the locating bearingwith a shaft opening (design BF), and that at theopposite end as the floating bearing with end cap (designAL).With the specified operating data the calculated indexof dynamic stressing f L ≈ 10; an f L value of 4...5 (correspondingto 55,000...100,000 h) would be adequate.Thus, the bearings are very safely dimensioned with regardto fatigue life. However, premature wear can becaused by slippage, ending the actual service life of thebearings before the calculated fatigue life has beenreached.The plummer blocks are made of grey cast iron. Thehousing bodies are split to simplify mounting.Machining tolerancesShaft to m6; housing to G6.Lubrication, sealingThe LOE housings feature an oil bath. A ring oilersupplies the bearings with oil. The design of the lateralhousing covers (oil collecting pockets and returnducts) allows excess oil to return to the sump.A grease chamber is provided as an additional sealingbetween cover and labyrinth ring; the chamber is replenishedwith grease at regular intervals.118: Rotor mounting of an exhauster169 FAG


119 Hot gas fanGas temperature 150 °C; thrust 3 kN; operating speed3,000 min –1 .Bearing selectionThe impeller of small and medium-sized fans is generallyoverhung. A particularly simple and economicalarrangement is achieved by providing a one-piecehousing incorporating two bearing mountings. Theoverhung impeller arrangement produces, however, atilting moment from the impeller weight and unbalancedforces acting at the impeller. The radial loads resultingfrom this moment can be minimized by providinga large distance between the bearing locationsin relation to the distance between the impeller andthe first bearing location. This requirement is satisfiedby plummer block housings of series FAG VR(E)(grease lubrication) or FAG VOS (oil lubrication) whichwere especially developed for fan applications. Sincethe operating speed is relatively high, bearings with ahigh speed suitability are used, e.g. cylindrical rollerbearings for accommodating the radial loads and angularcontact ball bearings for combined (i.e. radial andthrust) loads. The shaft diameter, dictated by strengthconsiderations, is 85 mm.The mounting consists of a plummer block housing(series VOS) for oil lubrication FAG VOB317. At theimpeller end a cylindrical roller bearing FAGNU317E.M1.C3 acts as the floating bearing, at thedrive end two universal angular contact ball bearingsFAG 7317B.MP.UA are mounted in O arrangement.Suffix UA identifies bearings which can be universallymounted in tandem, O or X arrangement; the X and Oarrangements feature a small axial clearance. The axialclearance combined with oil lubrication prevents overheatingof the bearings and thus preloading.Machining tolerancesCylindrical roller bearing: Shaft to m5; housing to K6.Angular contact ballbearings: Shaft to k6; housing to J6.Lubrication, sealingOil lubrication. The oil sump in the housing containsapproximately 4 l of oil. Flinger rings feed the oil to thebearings. The sleeves mounted on the shaft featureflinger grooves. Oil collecting grooves and replenishablegrease chambers are provided in the housing covers.Floating bearingLocating bearing119: Rotor bearings of a hot gas ventilatorFAG 170


120 Fresh air blowerWeight of impeller 0.5 kN, weight of shaft 0.2 kN,thrust 0.3 kN; speed 3,000 min –1 .Bearing selectionSince a simple and economical mounting is required, aplummer block FAG SNV120.G944AA with a selfaligningball bearing FAG 2311K.TV.C3 is arranged ateither side of the impeller. Self-aligning bearings arenecessary because of the difficulty in aligning two separatelymounted housings so accurately that the boresare exactly aligned.The housing is suitable for grease replenishment (suffixG944AA). A grease nipple is provided at the housingcap and a grease escape bore at the opposite side of thehousing base.As long as the impeller is satisfactorily balanced the innerrings of the bearings are circumferentially loaded.They are mounted on the shaft with adapter sleevesFAG H2311. However, when the imbalance forces exceedthe weight of impeller and shaft the circumferentialload is transmitted to the outer ring.Calculation of the rating fatigue life shows that thebearings are more than adequately dimensioned.The SNV housings are made of grey-cast iron. Thehousing bodies are split to simplify mounting.Machining tolerancesShaft to h9, cylindricity tolerance IT6/2 (DIN ISO1101); housing to H7.Lubrication, sealingThe bearings are lubricated with FAG rolling bearinggrease Arcanol L71V.The housing is sealed on each side by an FSV felt seal.120: Rotor mounting of a fresh air blower171 FAG


121 Optical telescopeOperating dataThe telescope is approximately 7 m high, 8 m long andweighs about 10 t, corresponding to 100 kN. The mirrordiameter is 1 m. Due to the extremely low speed ofrotation of the yoke axle (1 revolution in 24 hours), avery low and uniform bearing friction is required.Moreover, the yoke must be guided rigidly and withabsolute zero clearance. Deflection of the yoke axleunder the effect of the overhanging load must also betaken into account.Lubrication, sealingGrease lubrication (FAG rolling bearing grease ArcanolL186V). The cylindrical roller bearing is fitted with agap-type seal with grease grooves, the angular contactball bearing is sealed by a labyrinth.Bearing selectionThe locating bearing at the upper end of the yoke supportis a high-precision double-row angular contactball bearing with split outer ring. Its dimensions are600 x 730 x 98 mm. The gap width between the twoouter rings is such that, when adjusting the bearingaxially, a preload of 35 kN is obtained. The lower endof the yoke axle is supported by a cylindrical rollerbearing FAG NU1044K.M1.P51 acting as the floatingbearing.Floating bearingLocating bearingYoke mass2,500 kgTelescope mass2,500 kgBearing assemblyDespite the large diameter of the yoke axle, the deflectionstill existing would result in increased friction inthe preloaded angular contact ball bearing unless suitablecountermeasures were taken. The problem wassolved by mounting the cylindrical roller bearing intwo outer shroud rings whose inside diameters are eccentricto the outside diameter. These shroud rings arerotated in opposite directions during mounting (D)until the shaft deflection at the angular contact ballbearing location is equalized. The crowned inner ringraceway of the cylindrical roller bearing allows forslight misalignments and shaft deflections.Machining tolerancesBearing Seat Diameter Form tolerance Axial run-out tolerance oftolerance (DIN ISO 1101) abutment shoulderAngular contact ball bearingCylindrical roller bearingShaft j5 IT2/2 IT2Housing J6 IT3/2 IT2Shaft, tapered taper 1 : 12 IT2/2 IT2Housing K6 IT3/2 IT2FAG 172


Floating bearingLocating bearingBending momentShroud rings121: Optical telescope173 FAG


122–124 RadiotelescopeFor radioastronomy highly sensitive radiotelescopes areused for picking up radio waves from the universe.The radiotelescope antenna is a huge reflector in theform of a paraboloid. The reflector is slewable aboutan axis parallel to the earth surface, the elevation axis.The whole telescope slews about the vertical axis, theazimuth axis.Operating dataTotal mass of the radiotelescope 3,000 tons (loadapproximately 30,000 kN); reflector diameter 100 m,reflector mass 1,600 tons (load approximately16,000 kN); speed of track rollers n max = 8 min –1 ,n min = 0.01 min –1 ; track diameter 64 m.A ReflectorB Azimuth axisC Elevation axisD King pin bearingE Travelling gear (track rollers)F Data wheelFAG 174


122 Elevation axisThe reflector is supported on two spherical roller bearingsFAG 241/850BK30.P62 (static load rating C 0 =49,000 kN). Each of the two bearings has to accommodatea radial load of 8,000 kN. Added to this arethe loads resulting from the effects of wind and snowon the reflector. Maximum loads in the horizontal directionmay be 5,500 kN, in the vertical direction3,000 kN. Bearing centre distance is 50 m. The bearingsfeature tolerance class P6 and radial clearance C2(smaller than normal clearance CN). The bearings aremounted onto the journals with tapered sleeves bymeans of the hydraulic method. During mounting theradial clearance is eliminated by driving in the sleeves.Machining tolerancesJournal to h7 / housing to H6Lubrication, sealingThe spherical roller bearings are lubricated with FAGrolling bearing grease Arcanol L135V.The bearings are sealed by a rubbing seal.122: Elevation axis175 FAG


123 Azimuth axis (track roller and king pin bearings)The radiotelescope with its complete superstructure issupported on a circular track of 64 m diameter. Theroller track assembly, comprising four groups of eightrollers each, transmits the weight of approximately30,000 kN.Every second roller of a roller group is driven. Eachroller is supported on two spherical roller bearingsFAG 23060K.MB.C2. The bearings are mounted onthe journal with withdrawal sleeves FAG AH3060H.In the most adverse case one bearing has to accommodateapproximately 800 kN. With the static load ratingC 0 = 3,550 kN the bearings are safely dimensioned.The outer rings of the bearings are mounted into thehousings with axial clearance so that a floating bearingarrangement is obtained. Since low friction is requiredthe rollers to not incorporate wheel flanges. Thus it isnecessary to radially guide the superstructure on a kingpin bearing. The FAG cylindrical roller bearing providedfor this purpose has the dimensions 1,580 x2,000 x 250 mm. The cylindrical roller outside diametersare slightly crowned in order to avoid edge stressing.By mounting the bearing with a tapered sleeve theradial clearance can be eliminated, thus providing accurateradial guidance.Machining tolerancesTrack rollers: Housing to H7King pin: Journal to h7/ housing to M7Lubrication, sealingThe spherical roller bearings in the track rollers arelubricated with FAG rolling bearing grease ArcanolL135V. The cylindrical roller bearing for the king pinfeatures circulating oil lubrication.Sealing by multiple labyrinths.123a: Roller track assembly123b: King pin bearingFAG 176


124 Data wheelThe data wheel is supported on a clearance-free FAGfour-point bearing with the dimensions 1,300 x 1,500x 80 mm.Radial runout < 10 µm,Axial runout < 25 µm.Lubrication, sealingThe four-point bearing is fully immersed in oil.Sealing by a multiple labyrinth.Machining tolerancesThe four-point bearing is fitted according to the actualbearing dimensions.124: Data wheel177 FAG


GlossaryAdditivesAdditives are oil-soluble substances added to mineraloils or mineral oil products. By chemical or physicalaction, they change or improve lubricant properties(oxidation stability, EP properties, foaming, viscositytemperaturebehaviour, setting point, flow properties,etc.). Additives are also an important factor in calculatingthe attainable life (cp. also Factor K).Adjusted bearing arrangement/ AdjustmentAn adjusted bearing arrangement consists of two symmetricallyarranged angular contact bearings or thrustbearings. During mounting, one bearing ring (for an Oarrangement, the inner ring; for an X arrangement, theouter ring) is displaced on its seat until the bearing arrangementhas the appropriate axial clearance or the requiredpreload. This means that the adjusted bearingarrangement is particularly suitable for those caseswhere a close axial guidance is required, for example,for pinion bearing arrangements with spiral toothedbevel gears.Adjusted bearing arrangement(O arrangement)Adjusted bearing arrangement(X arrangement)Adjusted rating life calculationThe nominal life L or L h deviates more or less from thereally attainable life of rolling bearings.Therefore, the adjusted rating life calculation takesinto account, in addition to the load, the failure probability(factor a 1 ) and other significant operating conditions(factor a 23 in the FAG procedure for calculatingthe attainable life).Cp. also Modified life in accordance with DIN ISO 281.AlignmentSelf-aligning bearings are used to compensate for misalignmentand tilting.Angular contact bearingsThe term "angular contact bearing" is collectively usedfor single-row bearings whose contact lines are inclinedto the radial plane. So, angular contact bearings are angularcontact ball bearings, tapered roller bearings andspherical roller thrust bearings. Axially loaded deepgroove ball bearings also act in the same way as angularcontact bearings.Arcanol (FAG rolling bearing greases)FAG rolling bearing greases Arcanol are field-provenlubricating greases. Their scopes of application were determinedby FAG by means of the latest test methodsunder a large variety of operating conditions and withrolling bearings of all types. The eight Arcanol greaseslisted in the table on page 179 cover almost all demandson the lubrication of rolling bearings.Attainable life L na , L hnaThe FAG calculation method for determining the attainablelife (L na , L hna ) is based on DIN ISO 281 (cp.Modified life). It takes into account the influences ofthe operating conditions on the rolling bearing life andindicates the preconditions for reaching endurancestrength.L na =a 1 · a 23 · L [10 6 revolutions]andL hna =a 1 · a 23 · L h [h]a 1 factor a 1 for failure probability(DIN ISO 281);for a normal (10%) failure probability a 1 = 1.a 23 factor a 23 (life adjustment factor)L nominal rating life [10 6 revolutions]L h nominal rating life [h]If the quantities influencing the bearing life (e. g. load,speed, temperature, cleanliness, type and condition oflubricant) are variable, the attainable life (L hna1 ,L hna2 , ...) under constant conditions has to be determinedfor every operating time q [%]. The attainablelife is calculated for the total operating time using theformulaL hna =100q 1 +q 2 +q 3L hna1 L hna2 L hna3FAG 178


GlossaryArcanol rolling bearing greases · Chemo-physical data · Directions for useArcanol Thickener Base oil Consistency Temperature Colour Main characteristicsBase oil viscosity NLGI- range Typical applicationsat 40°C Classmm 2 /s DIN 51818 °C RALL12V Polyurea ISO VG 2 –30...+160 2002 Special grease for high temperaturesMineral oil 100 vermillionCouplings, electric machines(motors, generators)L71V Lithium soap ISO VG 3 –30...+140 4008 Standard grease for bearings with O.D.s > 62 mmMineral oil 100 signal violetLarge electric motors,wheel bearings for motor vehicles,ventilatorsL74V Special soap ISO VG 2 –40...+120 6018 Special grease for high speeds and low temperaturesSynthetic 22 yellow-greenoilMachine tools,spindle bearings,instrumentsL78V Lithium soap ISO VG 2 –30...+130 1018 Standard grease for bearings with O.D.s ≤ 62 mmMineral oil 100 zinc yellowSmall electric motors,agricultural and construction machinery,household appliancesL79V Synthetic 390 2 –30...+270 1024 Special grease for extremely high temperatures andSynthetic yellow ochre chemically aggressive environmentsoilTrack rollers in bakery machines,piston pins in compressors,kiln trucks, chemical plants(please observe safety data sheet)L135V Lithium soap 85 2 –40...+150 2000 Special grease for high loads,wit EP additivesyellow orange high speeds, high temperaturesMineral oilRolling mills, construction machinery,motor vehicles, rail vehicles,spinning and grinding spindlesL186V Lithium soap ISO VG 2 –20...+140 7005 Special grease for extremely high loads,with EP additives 460 mouse-grey medium speeds, medium temperaturesMineral oilHeavily stressed mining machinery,construction machinery,machines with oscillating movementsL223V Lithium soap ISO VG 2 –10...+140 5005 Special grease for extremely high loads, low speedswith EP additives 1000 signal blueMineral oilHeavily stressed mining machinery,construction machinery,particularly for impact loads and large bearings179 FAG


GlossaryAxial clearanceThe axial clearance of a bearing is the total possible axialdisplacement of one bearing ring measured withoutload. There is a difference between the axial clearanceof the unmounted bearing and the axial operating clearanceexisting when the bearing is mounted and runningat operating temperature.load. This ring is circumferentially loaded. Bearingswith circumferential load must be mounted with atight fit to avoid sliding (cp. Point load, Oscillatingload ).Circumferentialload on innerringImbalanceBase oilis the oil contained in a lubricating grease. The amountof oil varies with the type of thickener and the greaseapplication. The penetration number and the frictionalbehaviour of the grease vary with the amount of baseoil and its viscosity.Basic a 23II valueWeightRotating inner ringConstant load directionCircumferentialload on outerringStationary inner ringDirection of load rotatingwith outer ringImbalanceThe basic a 23II value is the basis for determining factora 23 , used in attainable life calculation.Bearing lifeThe life of dynamically stressed rolling bearings, as definedby DIN ISO 281, is the operating time until failuredue to material fatigue (fatigue life).By means of the classical calculation method, a comparisoncalculation, the nominal rating life L or L h , isdetermined; by means of the refined FAG calculationprocess, the attainable life L na or L hna is determined (seealso factor a 23 ).CageThe cage of a rolling bearing prevents the rolling elementsfrom rubbing against each other. It keeps themevenly spaced and guides them through unloaded sectionsof the bearing circumference.The cage of a needle roller bearing also has to guidethe needle rollers parallel to the axis. In the case of separablebearings the cage retains the rolling element set,thus facilitating bearing mounting. Rolling bearingcages are classified into the categories pressed cages andmachined/moulded cages.Circumferential loadIf the ring under consideration rotates in relation tothe radial load, the entire circumference of the ring is,during each revolution, subjected to the maximumWeightRotating outer ringConstant load directionCleanliness factor sThe cleanliness factor s quantifies the effect of contaminationon the attainable life. The product of s and thebasic a 23II factor is the factor a 23 .Contamination factor V is required to determine s.s = 1 always applies to normal cleanliness (V = 1).With improved cleanliness (V = 0.5) and utmostcleanliness (V = 0.3) a cleanliness factor s > 1 is obtainedfrom the right diagram (a) on page 181, basedon the stress index f s* and depending on the viscosityratio .s = 1 applies to < 0.4.With V = 2 (moderately contaminated lubricant) toV = 3 (heavily contaminated lubricant), s < 1 is obtainedfrom diagram (b).Combined loadStationary outer ringDirection of load rotatingwith inner ringThis applies when a bearing is loaded both radially andaxially, and the resulting load acts, therefore, at theload angle .Depending on the type of load, the equivalent dynamicload P or the equivalent static load P 0 is determinedwith the radial component F r and the thrust componentF a of the combined load.FAG 180


GlossaryDiagram for determining the cleanliness factor sa Diagram for improved to utmost cleanlinessb Diagram for moderately contaminated lubricant and heavily contaminated lubricantκ=4κ=3.5κ=3κ=2.5κ=2κ=1.5κ=1κ=0.9κ=0.8κ=0.7V = 1V = 0.5 V = 0.3κ=0.6κ=0.5a:b:2.5 3 4 5 6 7 8 9 10 12 14 16 20 1 2 3 5 10 15 20 30Stress index f s*Cleanliness factor s1V = 1 0.70.5V = 20.30.2V = 3A cleanliness factor s > 1 is attainable for fullcomplementbearings only if wear in roller/roller0.1contact is eliminated by a high-viscosity lubricantand utmost cleanliness (oil cleanliness according0.05to ISO 4406 at least 11/7).0.03Cleanliness factor sConsistencyMeasure of the resistance of a lubricating grease tobeing deformed.Consistency classification to NLGI, cp. Penetration.Contact angle The contact angle is the angle formed by the contactlines of the rolling elements and the radial plane of thebearing. 0 refers to the nominal contact angle, i.e. thecontact angle of the load-free bearing.Under axial loads the contact angle of deep groove ballbearings, angular contact ball bearings etc. increases.Under a combined load it changes from one rolling elementto the next. These changing contact angles aretaken into account when calculating the pressure distributionwithin the bearing.Ball bearings and roller bearings with symmetrical rollingelements have identical contact angles at their innerrings and outer rings. In roller bearings with asymmetricalrollers the contact angles at inner ring and outerring are not identical. The equilibrium of forces inthese bearings is maintained by a force componentwhich is directed towards the lip.Contact lineαThe rolling elements transmit loads from one bearingring to the other in the direction of the contact lines.181 FAG


GlossaryContamination factor VThe contamination factor V indicates the degree ofcleanliness in the lubricating gap of rolling bearingsbased on the oil cleanliness classes defined in ISO4406.When determining the factor a 23 and the attainablelife, V is used, together with the stress index f s* and theviscosity ratio , to determine the cleanliness factor s.V depends on the bearing cross section (D – d)/2, thetype of contact between the mating surfaces and especiallythe cleanliness level of the oil.If hard particles from a defined size on are cycled inthe most heavily stressed contact area of a rolling bearing,the resulting indentations in the contact surfaceslead to premature material fatigue. The smaller thecontact area, the more damaging the effect of a particleabove a certain size when being cycled. Small bearingswith point contact are especially vulnerable.According to today's knowledge the following cleanlinessscale is useful (the most important values are inboldface):V = 0.3 utmost cleanlinessV = 0.5 improved cleanlinessV = 1 normal cleanlinessV = 2 moderately contaminated lubricantV = 3 heavily contaminated lubricantPreconditions for utmost cleanliness (V = 0.3):– bearings are greased and protected by seals or shieldsagainst dust by the manufacturer– grease lubrication by the user who fits the bearingsinto clean housings under top cleanliness conditions,lubricates them with clean grease and takescare that dirt cannot enter the bearing during operation– flushing the oil circulation system prior to the firstoperation of the cleanly fitted bearings and takingcare that the oil cleanliness class is ensured duringthe entire operating timeGuide values for VPoint contactLine contactrequired guide values for required oil guide valuesoil cleanliness filtration ratio cleanliness class for filtration ratio(D-d)/2 V class according to according to according toaccording to ISO 4406 ISO 4572 ISO 4406 ISO 4572mm0.3 11/8 3 ≥ 200 12/9 3 ≥ 2000.5 12/9 3 ≥ 200 13/10 3 ≥ 75≤ 12.5 1 14/11 6 ≥ 75 15/12 6 ≥ 752 15/12 6 ≥ 75 16/13 12 ≥ 753 16/13 12 ≥ 75 17/14 25 ≥ 750.3 12/9 3 ≥ 200 13/10 3 ≥ 750.5 13/10 3 ≥ 75 14/11 6 ≥ 75> 12.5...20 1 15/12 6 ≥ 75 16/13 12 ≥ 752 16/13 12 ≥ 75 17/14 25 ≥ 753 18/14 25 ≥ 75 19/15 25 ≥ 750.3 13/10 3 ≥ 75 14/11 6 ≥ 750.5 14/11 6 ≥ 75 15/12 6 ≥ 75> 20...35 1 16/13 12 ≥ 75 17/14 12 ≥ 752 17/14 25 ≥ 75 18/15 25 ≥ 753 19/15 25 ≥ 75 20/16 25 ≥ 750.3 14/11 6 ≥ 75 14/11 6 ≥ 750.5 15/12 6 ≥ 75 15/12 12 ≥ 75> 35 1 17/14 12 ≥ 75 18/14 25 ≥ 752 18/15 25 ≥ 75 19/16 25 ≥ 753 20/16 25 ≥ 75 21/17 25 ≥ 75The oil cleanliness class can be determined by means of oil samples by filter manufacturers and institutes. It is a measure of the probability oflife-reducing particles being cycled in a bearing. Suitable sampling should be observed (see e. g. DIN 51570). Today, online measuring instrumentsare available. The cleanliness classes are reached if the entire oil volume flows through the filter within a few minutes.To ensure a high degree of cleanliness flushing is required prior to bearing operation.For example, a filtration ratio 3 ≥ 200 (ISO 4572) means that in the so-called multi-pass test only one of 200 particles ≥ 3 µm passes the filter.Filters with coarser filtration ratios than 25 ≥ 75 should not be used due to the ill effect on the other components within the circulationsystem.FAG 182


GlossaryPreconditions for normal cleanliness (V = 1):– good sealing adapted to the environment– cleanliness during mounting– oil cleanliness according to V = 1– observing the recommended oil change intervalsPossible causes of heavy lubricant contamination(V = 3):– the cast housing was inadequatly cleaned– abraded particles from components which are subjectto wear enter the circulating oil system of themachine– foreign matter penetrates into the bearing due tounsatisfactory sealing– water which entered the bearing, also condensationwater, caused standstill corrosion or deterioration ofthe lubricant propertiesThe necessary oil cleanliness class according to ISO4406 is an objectively measurable level of the contaminationof a lubricant.In accordance with the particle-counting mehod, thenumber of all particles > 5 µm and all particles > 15 µmare allocated to a certain ISO oil cleanliness classs.For example, an oil cleanliness class 15/12 accordingto ISO 4406 means that between 16,000 and 32,000particles > 5 µm and between 2,000 and 4,000 particles> 15 µm are present per 100 ml of a fluid.A defined filtration ratio x should exist in order toreach the oil cleanliness required.The filtration ratio is the ratio of all particles > x µmbefore passing the filter to the particles > x µm whichhave passed the filter. For example, a filtration ratio 3 ≥ 200 means that in the so-called multi-pass test(ISO 4572) only one of 200 particles ≥ 3 µm passesthe filter.Counter guidanceAngular contact bearings and single-direction thrustbearings accommodate axial forces only in one direction.A second, symmetrically arranged bearing mustbe used for "counter guidance", i.e. to accommodatethe axial forces in the other direction.Curvature ratioIn all bearing types with a curved raceway profile theradius of the raceway is slightly larger than that of therolling elements. This curvature difference in the axialplane is defined by the curvature ratio . The curvatureratio is the curvature difference between the rollingelement radius and the slightly larger grooveradius.curvature ratio =groove radius – rolling element radiusrolling element radiusDynamic load rating CThe dynamic load rating C (see FAG catalogues) is afactor for the load carrying capacity of a rolling bearingunder dynamic load. It is defined, in accordancewith DIN ISO 281, as the load a rolling bearing cantheoretically accommodate for a nominal life L of 10 6revolutions (fatigue life).Dynamic stressing/dynamic loadRolling bearings are dynamically stressed when onering rotates relative to the other under load. The term"dynamic" does not refer, therefore, to the effect of theload but rather to the operating condition of the bearing.The magnitude and direction of the load can remainconstant.When calculating the bearings, a dynamic stress is assumedwhen the speed n amounts to at least 10 min –1(see Static stressing ).Endurance strengthTests by FAG and field experience have proved that,under the following conditions, rolling bearings can befail-safe:– utmost cleanliness in the lubricating gap(contamination factor V = 0.3)– complete separation of the components in rollingcontact by the lubricating film (viscosity ratio ≥ 4)– load according to stress index f s* ≥ 8183 FAG


GlossaryEP additivesWear-reducing additives in lubricating greases and lubricatingoils, also referred to as extreme pressure lubricants.Equivalent dynamic load PFor dynamically loaded rolling bearings operatingunder a combined load, the calculation is based on theequivalent dynamic load. This is a radial load for radialbearings and an axial and centrical load for axial bearings,having the same effect on fatigue as the combinedload. The equivalent dynamic load P is calculated bymeans of the following equation:P = X · F r + Y · F a[kN]F r radial load [kN]F a axial load [kN]X radial factor (see FAG catalogues)Y thrust factor (see FAG catalogues)Equivalent static load P 0Statically stressed rolling bearings which operate undera combined load are calculated with the equivalent staticload. It is a radial load for radial bearings and anaxial and centric load for thrust bearings, having thesame effect with regard to permanent deformation asthe combined load.The equivalent static load P 0 is calculated with theformula:P = X 0 · F r + Y 0 · F a[kN]F r radial load [kN]F a axial load [kN]X 0 radial factor (see FAG catalogues)Y 0 thrust factor (see FAG catalogues)Factor a 1Generally (nominal rating life L 10 ), 10 % failure probabilityis taken. The factor a 1 is also used for failureprobabilities between 10 % and 1 % for the calculationof the attainable life, see following table.Failureprobability % 10 5 4 3 2 1Fatiguelife L 10 L 5 L 4 L 3 L 2 L 1Factor a 1 1 0.62 0.53 0.44 0.33 0.21Factor a 23 (life adjustment factor)The a 23 factor is used to calculate the attainable life.FAG use a 23 instead of the mutually dependent adjustmentfactors for material (a 2 ) and operating conditions(a 3 ) indicated in DIN ISO 281.a 23 = a 2 · a 3The a 23 factor takes into account effects of:– amount of load (stress index f s* ),– lubricating film thickness (viscosity ratio ),– lubricant additives (value K),– contaminants in the lubricating gap (cleanlinessfactor s),– bearing type (value K).The diagram on page 185 is the basis for the determinationof the a 23 factor using the basic a 23II value. Thea 23 factor is obtained from the equation a 23II · s (s beingthe cleanliness factor).The viscosity ratio = / 1 and the value K are requiredfor locating the basic value. The most important zone(II) in the diagram applies to normal cleanliness(s = 1).The viscosity ratio is a measure of the lubricating filmdevelopment in the bearing. operating viscosity of the lubricant, depending on thenominal viscosity (at 40 °C) and the operating temperaturet (fig. 1). In the case of lubricating greases, is the operating viscosity of the base oil. 1 rated viscosity, depending on mean bearing diameterd m and operating speed n (fig. 2).The diagram (fig. 3) for determining the basic a 23IIfactor is subdivided into zones I, II and III.Most applications in rolling bearing engineering arecovered by zone II. It applies to normal cleanliness(contamination factor V = 1). In zone II, a 23 can be determinedas a function of by means of value K.With K = 0 to 6, a 23II is found on one of the curves inzone II of the diagram.With K > 6, a 23 must be expected to be in zone III. Insuch a case conditions should be improved so thatzone II can be reached.FAG 184


Glossary1: Average viscosity-temperature behaviour of mineraloils; diagram for determining the operating viscosity3: Basic a 23II factor for determining the factor a 23Operating temperature t [°C]12011010090807060504030202: Rated viscosity 1Rated viscosity ν 1mm 2s1 0005002001005020105101546322210068Viscosity [mm 2 /s]at 40 °C32022015068046015001000104 6 8 10 20 30 40 60 100 200 300Operating viscosity ν [mm 2 /s]50 000100 0001 0002 0005 00010 00020 000500n [min -1 ]200100310 20 50 100 200 500 1 000Mean bearing diameter d m = D+d2 [mm]50201052ZonesIIIIII201052a 23II10,50,2Transition to endurance strengthPrecondition: Utmost cleanliness in the lubricating gapand loads which are not too high, suitable lubricantNormal degree of cleanliness in the lubricating gap(with effective additives tested in rolling bearings,a 23 factors > 1 are possible even with < 0.4)Unfavourable lubricating conditionsContaminated lubricantUnsuitable lubricantsK=0K=1K=2K=3K=4K=5K=6II0,10,05 0,1 0,2 0,5 1 2 5 10νκ = ν1Limits of adjusted rating life calculationAs in the case of the former life calculation, only material fatigueis taken into consideration as a cause of failure for the adjusted lifecalculation. The calculated attainable life can only correspond tothe actual service life of the bearing when the lubricant service lifeor the life limited by wear is not shorter than the fatigue life.IIIIFatigue lifeThe fatigue life of a rolling bearing is the operatingtime from the beginning of its service until failure dueto material fatigue. The fatigue life is the upper limitof service life.The classical calculation method, a comparison calculation,is used to determine the nominal life L or L h ; bymeans of the refined FAG calculation process theattainable life L na or L hna is determined (see also a 23factor).FitsThe tolerances for the bore and for the outside diameterof rolling bearings are standardized in DIN 620(cp. Tolerance class). The seating characteristics requiredfor reliable bearing operation, which are dependenton the operating conditions of the application,are obtained by the correct selection of shaft and housingmachining tolerances.For this reason, the seating characteristics of the ringsare indicated by the shaft and housing tolerance symbols.Three factors should be borne in mind in the selectionof fits:185 FAG


Glossary1. Safe retention and uniform support of the bearingrings2. Simplicity of mounting and dismounting3. Axial freedom of the floating bearingThe simplest and safest means of ring retention in thecircumferential direction is achieved by a tight fit.A tight fit will support the rings evenly, a factor whichis indispensable for the full utilization of the load carryingcapacity. Bearing rings accommodating a circumferentialload or an oscillating load are always fittedtightly. Bearing rings accommodating a point load maybe fitted loosely.The higher the load the tighter should be the interferencefit provided, particularly for shock loading. Thetemperature gradient between bearing ring and matingcomponent should also be taken into account. Bearingtype and size also play a role in the selection of the correctfit.Floating bearingIn a locating/floating bearing arrangement the floatingbearing compensates for axial thermal expansion.Cylindrical roller bearings of NU and N designs, aswell as needle roller bearings, are ideal floating bearings.Differences in length are compensated for in thefloating bearing itself. The bearing rings can be giventight fits.Non-separable bearings, such as deep groove ball bearingsand spherical roller bearings, can also be used asfloating bearings. In such a case one of the two bearingrings is given a loose fit, with no axial mating surfaceso that it can shift freely on its seat.Floating bearing arrangementA floating bearing arrangement is an economical solutionwhere no close axial shaft guidance is required.The design is similar to that of an adjusted bearingarrangement. In a floating bearing arrangement, however,the shaft can shift relative to the housing by theaxial clearance s. The value s is determined dependingon the required guiding accuracy in such a way thatdetrimental axial preloading of the bearings is preventedeven under unfavourable thermal conditions.In floating bearing arrangements with NJ cylindricalroller bearings, length variations are compensated forin the bearings. Inner and outer rings can be fittedtightly.Non-separable radial bearings such as deep groove ballbearings, self-aligning ball bearings and spherical rollerbearings can also be used. One ring of each bearing –generally the outer ring – is given a loose fit.Grease, grease lubricationcp. Lubricating greaseGrease service lifeThe grease service life is the period from start-up untilthe failure of a bearing as a result of lubrication breakdown.The grease service life is determined by the– amount of grease– grease type (thickener, base oil, additives)– bearing type and size– type and amount of loading– speed index– bearing temperatureIndex of dynamic stressing f LThe value recommended for dimensioning can be expressed,instead of in hours, as the index of dynamicstressing f L . It is calculated from the dynamic load ratingC, the equivalent dynamic load P and the speedfactor f n .f L = C · f nPsThe f L value to be obtained for a correctly dimensionedbearing arrangement is an empirical value obtainedfrom field-proven identical or similar bearingmountings.The values indicated in various FAG publications takeinto account not only an adequate fatigue life but alsoother requirements such as low weight for light-weightconstructions, adaptation to given mating parts,higher-than-usual peak loads, etc. The f L values conformwith the latest standards resulting from technicalprogress. For comparison with a field-proven bearingmounting the calculation of stressing must, of course,be based on the same former method.Based on the calculated f L value, the nominal rating lifeL h in hours can be determined.FAG 186


GlossaryL h = 500 · f Lp[h]p = 3 for ball bearingsp = 10 for roller bearings and needle roller bearings3Index of static stressing f sThe index of static stressing f s for statically loaded bearingsis calculated to ensure that a bearing with an adequateload carrying capacity has been selected. It is calculatedfrom the static load rating C 0 and the equivalentstatic load P 0 .f s = C 0P 0The index f s is a safety factor against permanent deformationsof the contact areas between raceway and themost heavily loaded rolling element. A high f s value isrequired for bearings which must run smoothly andparticularly quietly. Smaller values suffice where amoderate degree of running quietness is required. Thefollowing values are generally recommended:f s = 1.5...2.5 for a high degreef s = 1...1.5 for a normal degreef s = 0.7...1 for a moderate degreeValue K 1a ball bearingsb tapered roller bearings, cylindrical roller bearingsc spherical roller bearings, spherical roller thrust bearings 3) , cylindrical roller thrust1), 3)bearings1), 2)d full complement cylindrical roller bearings4d3c2K 1 b1a00 2 4 6 8 10 12f s*1)Attainable only with lubricant filtering corresponding to V < 1, otherwiseK 1 ≥ 6 must be assumed.2)To be observed for the determination of : the friction is at least twice the valuein caged bearings. This results in higher bearing temperature.3)Minimum load must be observed.Value K 27654K 3 221κ=4κ=2κ=0.4**κ=0.700 2 4 6 8 10 12f s*K 2 equals for 0 for lubricants with additives with a corresponding suitability proof.** With 0.4 wear dominates unless eliminated by suitable additives.κ=1κ=0.35**κ=0.3**κ=0.25**κ=0.2**K valueThe K value is an auxiliary quantity needed to determinethe basic a 23II factor when calculating the attainablelife of a bearing.K = K 1 + K 2K 1 depends on the bearing type and the stress index f s* ,see diagram.K 2 depends on the stress index f s* and the viscosity ratio. The values in the diagram (below) apply to lubricantswithout additives and lubricants with additiveswhose effects in rolling bearings was not tested.With K = 0 to 6, the basic a 23II value is found on one ofthe curves in zone II of diagram 3 on page 185 (cp.factor a 23 ).Kinematically permissible speedThe kinematically permissible speed is indicated in theFAG catalogues also for bearings for which – accordingto DIN 732 – no thermal reference speed is defined.Decisive criteria for the kinematically permissiblespeed are e.g. the strength limit of the bearing componentsor the permissible sliding velocity of rubbingseals. The kinematically permissible speed can bereached, for example, with– specially designed lubrication– bearing clearance adapted to the operatingconditions– accurate machining of the bearing seats– special regard to heat dissipationLifeCp. also Bearing life.187 FAG


GlossaryLoad angleThe load angle is the angle between the resultantapplied load F and the radial plane of the bearing. It isthe resultant of the radial component F r and the axialcomponent F a :tan = F a /F rFβF rLubricating greaseLubricating greases are consistent mixtures of thickenersand base oils. The following grease types are distinguished:– metal soap base greases consisting of metal soaps asthickeners and lubricating oils,– non-soap greases comprising inorganic gellingagents or organic thickeners and lubricating oils– synthetic greases consisting of organic or inorganicthickeners and synthetic oils.Load ratingF aThe load rating of a bearing reflects its load carryingcapacity. Every rolling bearing has a dynamic load rating(DIN ISO 281) and a static load rating (DIN ISO76). The values are indicated in the FAG rolling bearingcatalogues.Locating bearingIn a locating/floating bearing arrangement, the bearingwhich guides the shaft axially in both directions is referredto as locating bearing. All bearing types whichaccommodate thrust in either direction in addition toradial loads are suitable. Angular contact ball bearingpairs (universal design) and tapered roller bearing pairsin X or O arrangement may also be used as locatingbearings.Locating/floating bearing arrangementWith this bearing arrangement the locating bearingguides the shaft axially in both directions; the floatingbearing compensates for the heat expansion differentialbetween shaft and housing. Shafts supported withmore than two bearings are provided with only onelocating bearing; all the other bearings must be floatingbearings.Lubricating oilRolling bearings can be lubricated either with mineraloils or synthetic oils. Today, mineral oils are most frequentlyused.Lubrication intervalThe lubrication interval corresponds to the minimumgrease service life of standard greases (see FAG publicationWL 81 115). This value is assumed if the greaseservice life for the grease used is not known.Machined/moulded cagesMachined cages of metal and textile laminated phenolicresin are produced in a cutting process. They aremade from tubes of steel, light metal or textile laminatedphenolic resin, or cast brass rings. Cages of polyamide66 (polyamide cages) are manufactured by injectionmoulding. Like pressed cages, they are suitable forlarge-series bearings.Machined cages of metal and textile laminated phenolicresin are mainly eligible for bearings of which onlysmall series are produced. Large, heavily loaded bearingsfeature machined cages for strength reasons.Machined cages are also used where lip guidance of thecage is required. Lip-guided cages for high-speed bearingsare often made of light materials, such as lightmetal or textile laminated phenolic resin to minimizethe inertia forces.Mineral oilsCrude oils and/or their liquid derivates.Cp. also Synthetic lubricants.FAG 188


GlossaryModified lifeThe standard Norm DIN ISO 281 introduced, in additionto the nominal rating life L 10 , the modified lifeL na to take into account, apart from the load, theinfluence of the failure probability (factor a 1 ), of thematerial (factor a 2 ) and of the operating conditions(factor a 3 ).DIN ISO 281 indicates no figures for the factor a 23(a 23 = a 2 · a 3 ). With the FAG calculation process for theattainable life (L na , L hna ), however, operating conditionscan be expressed in terms of figures by the factora 23 .O arrangementIn an O arrangement (adjusted bearing mounting) twoangular contact bearings are mounted symmetrically insuch a way that the pressure cone apex of the left-handbearing points to the left and the pressure cone apex ofthe right-hand bearing points to the right.With the O arrangement one of the bearing innerrings is adjusted. A bearing arrangement with a largespread is obtained which can accommodate a considerabletilting moment even with a short bearing distance.A suitable fit must be selected to ensure displaceabilityof the inner ring.NLGI classCp. Penetration.Nominal rating lifeThe standardized calculation method for dynamicallystressed rolling bearings is based on material fatigue (formationof pitting) as the cause of failure. The life formulais:[10 6 revolutions]PL 10 is the nominal rating life in millions of revolutionswhich is reached or exceeded by at least 90 % of a largegroup of identical bearings.In the formula,C dynamic load rating [kN]P equivalent dynamic load [kN]p life exponentp = 3 for ball bearingsp = 10/3 for roller bearings and needle roller bearings.Where the bearing speed is constant, the life can be expressedin hours.L 10 = L = (C) pL h10 = L h = L · 106 [h]n · 60n speed [min –1 ]L h can also be determined by means of the index of dynamicstressing f L .The nominal rating life L or L h applies to bearingsmade of conventional rolling bearing steel and the usualoperating conditions (good lubrication, no extremetemperatures, normal cleanliness).The nominal rating life deviates more or less from thereally attainable life of rolling bearings. Influences suchas lubricating film thickness, cleanliness in the lubricatinggap, lubricant additives and bearing type aretaken into account in the adjusted rating life calculationby the factor a 23 .Oil/oil lubricationsee Lubricating oil.Operating clearanceThere is a distinction made between the radial or axialclearance of the bearing prior to mounting and the radialor axial clearance of the mounted bearing at operatingtemperature (operating clearance). Due to tightfits and temperature differences between inner andouter ring the operating clearance is usually smallerthan the clearance of the unmounted bearing.Operating viscosity Kinematic viscosity of an oil at operating temperature.The operating viscosity can be determined by meansof a viscosity-temperature diagram if the viscosities attwo temperatures are known. The operating viscosityof mineral oils with average viscosity-temperature behaviourcan be determined by means of diagram 1 (page185).For evaluating the lubricating condition the viscosityratio (operating viscosity /rated viscosity 1 ) is formedwhen calculating the attainable life.Oscillating loadIn selecting the fits for radial bearings and angular contactbearings the load conditions have to be considered.With relative oscillatory motion between the radial189 FAG


Glossaryload and the ring to be fitted, conditions of "oscillatingload" occur. Both bearing rings must be given atight fit to avoid sliding (cp. circumferential load ).PenetrationPenetration is a measure of the consistency of a lubricatinggrease. Worked penetration is the penetration of agrease sample that has been worked, under exactly definedconditions, at 25 °C. Then the depth of penetration– in tenths of a millimetre – of a standard coneinto a grease-filled vessel is measured.Penetration of common rolling bearing greasesNLGI classWorked penetration(Penetration classes) 0.1 mm1 310...3402 265...2953 220...2504 175...205Point loadIn selecting the fits for the bearing rings of radial bearingsand angular contact bearings the load conditionshave to be considered. If the ring to be fitted and theradial load are stationary relative to each other, onepoint on the circumference of the ring is always subjectedto the maximum load. This ring is point-loaded.Since, with point load, the risk of the ring sliding onits seat is minor, a tight fit is not absolutely necessary.With circumferential load or oscillating load, a tight fitis imperative.WeightStationary inner ringConstant load directionPoint loadon innerringImbalanceRotating inner ringDirection of load rotatingwith inner ringPolyamide cageMoulded cages of glass fibre reinforced polyamidePA66-GF25 are made by injection moulding and areused in numerous large-series bearings.Injection moulding has made it possible to realize cagedesigns with an especially high load carrying capacity.The elasticity and low weight of the cages are of advantagewhere shock-type bearing loads, great accelerationsand decelerations as well as tilting of the bearingrings relative to each other have to be accommodated.Polyamide cages feature very good sliding and dry runningproperties.Cages of glass fibre reinforced polyamide 66 can beused at operating temperatures of up to 120 °C forextended periods of time. In oil-lubricated bearings,additives contained in the oil may reduce the cage life.At increased temperatures, aged oil may also have animpact on the cage life so that it is important to observethe oil change intervals.Precision bearings/precision designIn addition to bearings of normal precision (toleranceclass PN), bearings of precision design (precision bearings)are produced for increased demands on workingprecision, speeds or quietness of running.For these applications the tolerance classes P6, P6X,P5, P4 and P2 were standardized. In addition, somebearing types are also produced in the tolerance classesP4S, SP and UP in accordance with an FAG companystandard.Pressed cagePressed cages are usually made of steel, but sometimesof brass, too. They are lighter than machined metalcages. Since a pressed cage barely closes the gapbetween inner ring and outer ring, lubricating greasecan easily penetrate into the bearing. It is stored at thecage.Pressure cone apexWeightStationary outer ringConstant load directionPoint loadon outerringImbalanceRotating outer ringDirection of load rotatingwith outer ringThe pressure cone apex is that point on the bearingaxis where the contact lines of an angular contact bearingintersect. The contact lines are the generatrices ofthe pressure cone.In angular contact bearings the external forces act, notat the bearing centre, but at the pressure cone apex.This fact has to be taken into account when calculatingthe equivalent dynamic load P and the equivalentstatic load P 0 .FAG 190


GlossaryRelubrication intervalPeriod after which the bearings are relubricated. Therelubrication interval should be shorter than the lubricationinterval.Radial bearingsRadial bearings are those primarily designed to accommodateradial loads; they have a nominal contact angle 0 ≤ 45°. The dynamic load rating and the static loadrating of radial bearings refer to pure radial loads (seeThrust bearings).Radial clearanceThe radial clearance of a bearing is the total distanceby which one bearing ring can be displaced in theradial plane, under zero measuring load. There is a differencebetween the radial clearance of the unmountedbearing and the radial operating clearance of themounted bearing running at operating temperature.Rolling elementsThis term is used collectively for balls, cylindrical rollers,barrel rollers, tapered rollers or needle rollers inrolling contact with the raceways.Seals/SealingOn the one hand the sealing should prevent the lubricant(usually lubricating grease or lubricating oil ) fromescaping from the bearing and, on the other hand, preventcontaminants from entering into the bearing. Ithas a considerable influence on the service life of a bearingarrangement (cp. Wear, Contamination factor V ).A distinction is made between non-rubbing seals (e.g.gap-type seals, labyrinth seals, shields) and rubbingseals (e.g. radial shaft seals, V-rings, felt rings, sealingwashers).Radial clearance groupThe radial clearance of a rolling bearing must be adaptedto the conditions at the bearing location (fits, temperaturegradient, speed). Therefore, rolling bearingsare assembled into several radial clearance groups, eachcovering a certain range of radial clearance.The radial clearance group CN (normal) is such thatthe bearing, under normal fitting and operating conditions,maintains an adequate operating clearance. Theother clearance groups are:C2 radial clearance less than normalC3 radial clearance larger than normalC4 radial clearance larger than C3.Rated viscosity 1The rated viscosity is the kinematic viscosity attributedto a defined lubricating condition. It depends on thespeed and can be determined with diagram 2 (page185) by means of the mean bearing diameter and thebearing speed. The viscosity ratio (operating viscosity/rated viscosity 1 ) allows the lubricating condition tobe assessed (see also factor a 23 ).Self-aligning bearingsSelf-aligning bearings are all bearing types capable ofself-alignment during operation to compensate for misalignmentas well as shaft and housing deflection.These bearings have a spherical outer ring raceway.They are self-aligning ball bearings, barrel roller bearings,spherical roller bearings and spherical rollerthrust bearings.Thrust ball bearings with seating rings and S-typebearings are not self-aligning bearings because they cancompensate for misalignment and deflections only duringmounting and not in operation.Separable bearingsThese are rolling bearings whose rings can be mountedseparately. This is of advantage where both bearingrings require a tight fit.Separable bearings include four-point bearings, cylindricalroller bearings, tapered roller bearings, thrustball bearings, cylindrical roller thrust bearings andspherical roller thrust bearings.Non-separable bearings include deep groove ball bearings,single-row angular contact ball bearings, self-191 FAG


Glossaryaligning ball bearings, barrel roller bearings and sphericalroller bearings.Service lifeThis is the life during which the bearing operates reliably.The fatigue life of a bearing is the upper limit of its servicelife. Often this limit is not reached due to wear orlubrication breakdown (cpl. Grease service life).Speed factor f nThe auxiliary quantity f n is used, instead of the speedn [min –1 ], to determine the index of dynamic stressing,f L .f n = p √ 33 1 / 3np = 3for ball bearingsp= 10 for roller bearings and needle roller bearings3Speed index n · d mThe product from the operating speed n [min –1 ] andthe mean bearing diameter d m [mm] is mainly used forselecting suitable lubricants and lubricating methods.d m = D + d[mm]2D bearing outside diameter [mm]d bearing bore [mm]Speed suitabilityGenerally, the maximum attainable speed of rollingbearings is dictated by the permissible operating temperatures.This limiting criterion takes into accountthe thermal reference speed. It is determined on the basisof exactly defined, uniform criteria (reference conditions)in accordance with DIN 732, part 1 (draft).In catalogue WL 41 520 "FAG Rolling Bearings" a referenceis made to a method based on DIN 732, part 2,for determining the thermally permissible operatingspeed on the basis of the thermal reference speed for caseswhere the operating conditions (load, oil viscosity orpermissible temperature) deviate from the referenceconditions.The kinematically permissible speed is indicated also forbearings for which – according to DIN 732 – no thermalreference speed is defined, e. g. for bearings withrubbing seals.SpreadGenerally, the spread of a machine component supportedby two rolling bearings is the distance betweenthe two bearing locations. While the distance betweendeep groove ball bearings etc. is measured between thebearing centres, the spread with single-row angularcontact ball bearings and tapered roller bearings is thedistance between the pressure cone apexes.Static load/static stressingStatic stress refers to bearings carrying a load when stationary(no relative movement between the bearingrings).The term "static", therefore, relates to the operation ofthe bearings but not to the effects of the load. Themagnitude and direction of the load may change.Bearings which perform slow slewing motions or rotateat a low speed (n < 10 min –1 ) are calculated likestatically stressed bearings (cp. Dynamic stressing).Static load rating C 0The static load rating C 0 is that load acting on a stationaryrolling bearing which causes, at the centre ofthe contact area between the most heavily loaded rollingelement and the raceway, a total plastic deformationof about 1/10,000 of the rolling element diameter. Forthe normal curvature ratios this value corresponds to aHertzian contact pressure of about4,000 N/mm 2 for roller bearings,4,600 N/mm 2 for self-aligning ball bearings and4,200 N/mm 2 for all other ball bearings.C 0 values, see FAG rolling bearing catalogues.Stress index f s*In the attainable life calculation the stress index f s*represents the maximum compressive stress occurringin the rolling contact areas.f s* = C 0 /P 0*C 0 static load rating [kN]P 0* equivalent bearing load [kN]P 0* = X 0 · F r + Y 0 · F a [kN]F r dynamic radial force [kN]F a dynamic axial force [kN]X 0 radial factor (see catalogue)thrust factor (see catalogue)Y 0FAG 192


GlossarySynthetic lubricants/synthetic oilsLubricating oils produced by chemical synthesis; theirproperties can be adapted to meet special requirements:very low setting point, good V-T behaviour,small evaporation losses, long life, high oxidationstability.Thermally permissible operating speedFor applications where the loads, the oil viscosity or thepermissible temperature deviate from the referenceconditions for the thermal reference speed the thermallypermissible operating speed can be determined bymeans of diagrams.The method is described in FAG catalogue WL 41 520.Tandem arrangementA tandem arrangement consists of two or more angularcontact bearings which are mounted adjacent to eachother facing in the same direction, i.e. asymmetrically.In this way, the axial force is distributed over all bearings.An even distribution is achieved with universaldesignangular contact bearings.ThickenerThickener and base oil are the constituents of lubricatinggreases. The most commonly used thickeners aremetal soaps (e. g. lithium, calcium) as well as polyurea,PTFE and magnesium aluminium silicate compounds.Thrust bearingsBearings designed to transmit pure or predominantlythrust loading, with a nominal contact angle 0 > 45°,are referred to as thrust bearings.The dynamic load rating and the static load rating ofthrust bearings refer to pure thrust loads (cp. Radialbearings).Tolerance classThermal reference speedThe thermal reference speed is a new index of thespeed suitability of rolling bearings. In the draft ofDIN 732, part 1, it is defined as the speed at which thereference temperature of 70 °C is established. In FAGcatalogue WL 41 520 the standardized reference conditionsare indicated which are similar to the normaloperating conditions of the current rolling bearings(exceptions are, for example, spindle bearings, fourpointbearings, barrel roller bearings, thrust ball bearings).Contrary to the past (limiting speeds), the thermalreference speed values indicated in the FAG catalogueWL 41 520 now apply equally to oil lubricationand grease lubrication.For applications where the operating conditions deviatefrom the reference conditions, the thermally permissibleoperating speed is determined.In cases where the limiting criterion for the attainablespeed is not the permissible bearing temperature but,for example, the strength of the bearing componentsor the sliding velocity of rubbing seals the kinematicallypermissible speed has to be used instead of the thermalreference speed.In addition to the standard tolerance (tolerance classPN) for rolling bearings there are also the toleranceclasses P6, P6X, P5, P4 and P2 for precision bearings.The standard of precision increases with decreasingtolerance number (DIN 620).In addition to the standardized tolerance classes FAGalso produces rolling bearings in tolerance classes P4S,SP (super precision) and UP (ultra precision).Universal designSpecial design of FAG angular contact ball bearings.The position of the ring faces relative to the racewaybottom is so closely toleranced that the bearings can beuniversally mounted without shims in O, X or tandemarrangement.Bearings suffixed UA are matched together in such away that unmounted bearing pairs in O or X arrangementhave a small axial clearance. Under the same conditions,bearings suffixed UO feature zero axial clearance,and bearings suffixed UL a light preload. If thebearings are given tight fits the axial clearance of thebearing pair is reduced or the preload increased.193 FAG


GlossaryViscosityViscosity is the most important physical property of alubricating oil. It determines the load carrying capacityof the oil film under elastohydrodynamic lubricatingconditions. Viscosity decreases with rising temperatureand vice-versa (see V-T behaviour). Therefore it is necessaryto specify the temperature to which any givenviscosity value applies. The nominal viscosity 40 of anoil is its kinematic viscosity at 40 °C.SI units for the kinematic viscosity are m 2 /s andmm 2 /s. The formerly used unit Centistoke (cSt) correspondsto the SI unit mm 2 /s. The dynamic viscosity isthe product of the kinematic viscosity and the densityof a fluid (density of mineral oils: 0.9 g/cm 3 at 15 °C).Viscosity ratio With an X arrangement, the bearing clearance is obtainedby adjusting one outer ring. This ring should besubjected to point load because, being displaceable, itcannot be fitted tightly (Fits). Therefore, an X arrangementis provided where the outer ring is subjected topoint load or where it is easier to adjust the outer ringthan the inner ring. The effective bearing spread in anX arrangement is less than in an O arrangement.The viscosity ratio, being the quotient of the operatingviscosity and the rated viscosity 1 , is a measure of thelubricating film development in a bearing, cp. factora 23 .Viscosity-temperature behaviour (V-T behaviour)The term V-T behaviour refers to the viscosity variationsin lubricating oils with temperature. The V-T behaviouris good if the viscosity varies little with changingtemperatures.WearThe life of rolling bearings can be terminated, apartfrom fatigue, as a result of wear. The clearance of aworn bearing gets too large.One frequent cause of wear are foreign particles whichpenetrate into a bearing due to insufficient sealing andhave an abrasive effect. Wear is also caused by starvedlubrication and when the lubricant is used up.Therefore, wear can be considerably reduced by providinggood lubrication conditions (viscosity ratio > 2 if possible) and a good degree of cleanliness inthe rolling bearing. Where ≤ 0.4 wear will dominatein the bearing if it is not prevented by suitable additives(EP additives).X arrangementIn an X arrangement, two angular contact bearings aremounted symmetrically in such a way that the pressurecone apex of the left-hand bearing points to the rightand that of the right-hand bearing points to the left.FAG 194


Notes195 FAG


NotesFAG 196


The Design of Rolling Bearing MountingsEvery care has been taken to ensure the correctness of the information containedin this publication but no liability can be accepted for any errors or omissions.We reserve the right to make changes in the interest of technical progress.© by FAG 1998. This publication or parts thereof may not be reproduced without our permission.WL 00 200/5 EC/98,5/4/98Printed in Germany by Weppert GmbH & Co. KG, Schweinfurt