Sprag-Type Freewheel-Clutches

IntroductionMounting InstructionsSpeed LimitsGMN Sprag-Type-Clutches Series 8000Basic and Specific InformationThe sprag-type freewheel clutches ofseries 8000 are based on a newlydeveloped sprag with a nominal heightof 8.33 mm ( 21 /64 in). For shaft sizes of38 to 150 mm or corresponding inchsizes this series offers alternative optionsor additional solutions for our famousseries FE 400. Similar to FE 400 the new8000 series provides very high torquecapacity in relation to the requiredmounting space due to the largequantity of sprags. The newly designedclamping curve offers smooth andreliable torque pick up, which guaranteesoptimum performance for any freewheelclutch application such as indexing,overrunning or backstopping.The diameter range mentioned abovedoes not show the limits for the usage ofthis series. For special requirements ofour customers we will be pleased todevelop and offer new types below orabove the existing standard programme.We offer clutches of the 8000 series infour different widths: 13, 16, 19, 25 mm.The partnumber shows this dimension.The standard does not incorporate allwidths for any diameter right now, butmissing combinations will be realisedupon requirement. The two or three lastdigits of the part number show theclosest full shaft diameter of the metricconversion of the basically inch size ofthe metric conversion of the basicallyinch size of the shaft. e.g. FE 8072 for72.21 mm = 2 27 /32 in. Special clutchescould be designed for exact pure metricshafts or housings (just one of them at atime).The race ways the series 8000 insertclutches should run on must behardened and ground. When surfacehardening is used, the minimumhardening depth (Eht) at full torque mustbe 1.3 mm. Lower torque requirementsallow lower depths.The tolerances for the mating parts ofseries 8000 have not to be assofisticated as with series 400 due to thelarger size of the sprags and the differentshape of the clamping curve.Mounting fits:(only series 8000)Shaft: d L = h6Housing: D L = H6Hardness: HRC = 60 +4HardeningDepth: Eht ≥ 1.3 mmSurface Finish: R Z ≤ 2.5 µmExcentricity: e ≤ 0.09 mm(coaxiality of inner and outer race way)Axial limitation for the insert clutch will benecessary and can be arranged by ashoulder, a washer or snapring (roundedge towards the clutch). For ease ofmounting we recommend chamferedshafts and housings.When torque is transmitted the spragsare in a fixed position between innerandouter race. Under these conditons –theoretically – there is no speed limit. Inbackstopping and overrunningapplications the influence of centrifugalforces has to be considered.Tests showed that with oil lubricationseries 8000 sprags surf on ahydrodynamic lubricating film underconstant conditions (v = const.) withrotating shaft. The clutch itself turns veryslowly under these conditions and socentrifugal forces do not becomeeffective. The same situation could beexpected with grease lubrication at aslightly higher speed level.Due to the idling behaviour of our spragsof series 8000 there would be no needfor sprags lifting off by centrifugal forceor for dual cages or cages fix by clips orsprings.The rotating speed of the clutch itselfdepends on size, viscosity andtemperature. With a hydrodynamiclubricating film only minimal wear couldbe expected.Please note that in indexing applicationsdue to alternating conditions ahydrodynamic lubricating film cannot becreated. Please contact our technicalstaff for some advise if this kind ofapplications should arise.22