Page 26 - needle bearings

Calculation of Bearing Loads
NTN

3.1.2 Loads acting on chain and belt shafts where
In the case of power transmission by a chain and a K ɿActual load acting on shaft N(kgf)
belt, the load acting tangentially on the sprocket or the Kc ɿTheoretically calculated value N (kgf)
pulley can be determined by formula (3.7). fw ɿLoad factor (Table 3.4)

6
6
19.1ʷ10 ɾHP 1.95ʷ10 ɾHP Table 3.4 Load factor fw
ʢ
ʣ
Ktʹʕʕʕʕʕʕʕʕʕ ʕʕʕʕʕʕʕʕʕ ʜʜʜʜʜʜ(3.7)
Dpɾn Dpɾn
Extent of shock fw Application
where, Electrical machines, machine tools,
Nearly no shock 1.0ʙ1.2
Kt ɿTangential load acting on sprocket or pulley N (kgf) measuring instruments
Railway vehicles, automobiles,
HPɿTransmission power kW rolling mills, metal working machines,
paper making machines, rubber mixing
Dp ɿPitch circle diameter of sprocket or pulley mm Light shock 1.2ʙ1.5 machines, printing machines, aircraft,
textile machines, electrical units,
office equipment
In the case of belt driving, initial tension is applied to
the belt so the pulley and the belt are both always Heavy shock 1.5ʙ3.0 Crushers, agricultural machines,
construction machines, cranes
pressed down with a proper load.
F1Slackening side
3.2 Load distribution to bearings
Dp Any loads acting on shafts are distributed to the
Kr bearings considering static tension to be supported with
the bearings.
For example, the loads acting on the bearings in the
F2 Tension side
gear shaft illustrated in Fig. 3.7 can be expressed in
Fig. 3.6 Loads acting on chain/ belt formulas (3.10) and (3.11).

b c Dp
Considering this initial tension, radial load acting on the FrAʹKr!ʕʕʵKr@ʕʕʵKaʕʕʜʜʜʜʜʜʜʜ(3.10)
pulley is expressed in formula (3.8). l l 2l
In the case of chain driving, the radial load acting
thereon can be expressed using the same formula, if
a aʴbʴc Dp
vibration and shock are taken into consideration. FrBʹKr!ʕʕʴKr@ʕʕʕʕʕʕʴKaʕʕ ʜʜʜʜʜ(3.11)
l l 2l
Krʹf bɾKt ʜʜʜʜʜʜʜʜʜʜʜʜʜʜʜʜʜ(3.8)
where,
where, FrA ɿRadial load acting on bearing-A N (kgf)
FrB ɿRadial load acting on bearing-B N (kgf)
KrɿRadial load acting on sprocket or pulley N (kgf)
Kr1ɿRadial load acting on gear-! N (kgf)
f bɿChain/belt factor (Table 3.3) Ka ɿAxial load acting on gear-! N (kgf)
Kr2ɿAxial load acting on gear-!! N (kgf)
Table 3.3 Chain/belt factor f b Dp ɿPitch circle diameter of gear-! mm
Type of chain / belt f b l ɿBearing to bearing distance mm
Chain (single row type) 1.2ʙ1.5
Vee-belt 1.5ʙ2.0
Timing belt 1.1ʙ1.3
Gear-!!
Flat belt (with tension pulley) 2.5ʙ3.0 l
Gear-!
Flat belt 3.0ʙ4.0
Ka
Kr! Kr@
Dp
FrA FrB
3.1.3 Load factor
In an actual machine, the shaft load is mostly greater Bearing-A Bearing-B
than the theoretically calculated load due to vibration,
shock, etc. The load acting on the shafts of a machine a b c
can be determined by formula (3.9).
Kʹ fWɾKC ʜʜʜʜʜʜʜʜʜʜʜʜʜʜʜʜʜ(3.9) Fig. 3.7 Gear shaft

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