Needle Roller Bearings - Ntn-snr.com

Calculation of Bearing Loads
NTN
3.1.2 Loads acting on chain and belt shafts
In the case of power transmission by a chain and a
belt, the load acting tangentially on the sprocket or the
pulley can be determined by formula (3.7).
19.110 6 HP 1.9510 6 HP
Kt
(3.7)
Dpn
Dpn
where,
Kt Tangential load acting on sprocket or pulley N (kgf)
HPTransmission power kW
Dp Pitch circle diameter of sprocket or pulley mm
In the case of belt driving, initial tension is applied to
the belt so the pulley and the belt are both always
pressed down with a proper load.
where
K Actual load acting on shaft N(kgf)
Kc Theoretically calculated value N (kgf)
fw Load factor (Table 3.4)
Table 3.4 Load factor fw
Extent of shock
Nearly no shock 1.01.2
Light shock
Heavy shock
fw
1.21.5
1.53.0
Application
Electrical machines, machine tools,
measuring instruments
Railway vehicles, automobiles,
rolling mills, metal working machines,
paper making machines, rubber mixing
machines, printing machines, aircraft,
textile machines, electrical units,
office equipment
Crushers, agricultural machines,
construction machines, cranes
Dp
F1
F2
Slackening side
Kr
Tension side
Fig. 3.6 Loads acting on chain/ belt
3.2 Load distribution to bearings
Any loads acting on shafts are distributed to the
bearings considering static tension to be supported with
the bearings.
For example, the loads acting on the bearings in the
gear shaft illustrated in Fig. 3.7 can be expressed in
formulas (3.10) and (3.11).
Considering this initial tension, radial load acting on the
pulley is expressed in formula (3.8).
In the case of chain driving, the radial load acting
thereon can be expressed using the same formula, if
vibration and shock are taken into consideration.
Krf bKt (3.8)
where,
KrRadial load acting on sprocket or pulley N (kgf)
f bChain/belt factor (Table 3.3)
Table 3.3 Chain/belt factor f b
Type of chain / belt
Chain (single row type)
Vee-belt
Timing belt
Flat belt (with tension pulley)
Flat belt
f b
1.21.5
1.52.0
1.11.3
2.53.0
3.04.0
b c Dp
FrAKr!Kr@Ka(3.10)
l l 2l
a abc Dp
FrBKr!Kr@Ka
l l 2l
(3.11)
where,
FrA Radial load acting on bearing-A N (kgf)
FrB Radial load acting on bearing-B N (kgf)
Kr1 Radial load acting on gear-! N (kgf)
Ka Axial load acting on gear-! N (kgf)
Kr2 Axial load acting on gear-! N (kgf)
Dp Pitch circle diameter of gear-! mm
l Bearing to bearing distance mm
l
Gear-!
Gear- !
Kr!
Ka
Kr@
Dp
3.1.3 Load factor
In an actual machine, the shaft load is mostly greater
than the theoretically calculated load due to vibration,
shock, etc. The load acting on the shafts of a machine
can be determined by formula (3.9).
K fWKC
(3.9)
FrA
Bearing-A
FrB
Bearing-B
a
b
Fig. 3.7 Gear shaft
c
A-22