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●Bearing Load Calculation
4. Bearing Load Calculation
To compute bearing loads, the forces which act on the shaft being supported by the bearing must be determined. Loads which act on the shaft and its related parts include dead load of the rotator, load produced when the machine performs work, and load produced by transmission of dynamic force. These can theoretically be mathematically calculated, but calculation is difficult in many cases.

Ks ＝ Kt・tanα（Spur gear） ……（4.3a） tanα ＝ Kt・cosβ （Helical gear）……（4.3b）
Kr ＝ √ t ＋Ks ………………………（4.4）
K
2

2

Ka ＝ Kt・tanβ（Helical gear） ……（4.5） where, Kt ：Tangential gear load (tangential force), N {kgf}
Ks ：Radial gear load (separating force), N {kgf}
Kr ：Right angle shaft load (resultant force of tangential force and separating force), N {kgf}
Ka：Parallel load on shaft, N {kgf}
H ：Transmission force , kW
-1
n ：Rotational speed, min
Dp：Gear pitch circle diameter, mm α：Gear pressure angle, deg β：Gear helix angle, deg

A method of calculating loads that act upon shafts that convey dynamic force, which is the primary application of bearings, is provided herein.

4.1 Load acting on shafts
4.1.1 Load factor
There are many instances where the actual operational shaft load is much greater than the theoretically calculated load, due to machine vibration and/or shock.
This actual shaft load can be found by using formula
(4.1).

Because the actual gear load also contains vibrations and shock loads as well, the theoretical load obtained by the above formula should also be adjusted by the gear factor fz as shown in Table 4.2.

K ＝ fw・Kc ……………………………（4.1） where, K ：Actual shaft load N｛kgf｝ fw ：Load factor (Table 4.1)
Kc：Theoretically calculated value N｛kgf｝
Table 4.1 Load factor fw
Amount
of shock

fw

Application

Very little or no shock

Light shock

Railway vehicles, automobiles, rolling mills, metal working machines,
1.2∼1.5 paper making machines, printing
machines,