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### Flat Ring Thrust Bearing Moment Resistance Calculator

Flat Ring Thrust Bearing Frictional Moment Resistance Calculator

Step thrust bearings or pivots may be used to resist the end thrust of shafts. Let L = total load in the direction of the shaft axis and f = coefficient of sliding friction.

Figure 1, Flat Ring Bearing

For a ring-shaped flat step bearing such as that shown in figure 1 (or a collar bearing), the moment of thrust friction

Eq. 1

$M=1/3fL\frac{\left({D}^{3}-{d}^{3}\right)}{\left({D}^{2}-{d}^{2}\right)}$

The value of the coefficient of sliding friction is 0.08 to 0.15 when the speed of rotation is very slow. At higher velocities when a collar or step bearing is used, f = 0.04 to 0.06. If the design provides for the formation of a load carrying oil film, as in the case of the Kingsbury thrust bearing, the coefficient of friction has values f = 0.001 to 0.0025.

Where oil is supplied from an external pump with such pressure as to separate the surfaces and provide an oil film of thickness h (Figure 1) the frictional moment is

For a flat circular step bearing,

Eq. 2

d = 0

$M=1/3fLD$

Eq. 3

$M=\frac{Zn\left({D}^{4}-{d}^{4}\right)}{\left(67x{10}^{7}\right)h}$

Eq. 4

$M=\frac{\pi \mu \omega \left({D}^{4}-{d}^{4}\right)}{32h}$

where D and d are in inches, µ the absolute viscosity, ω the angular velocity, h is the film thickness, in, Z is viscosity of lubricant in centipoises, and n is rotation speed, r/min. With this kind of lubrication the frictional moment depends upon the speed of rotation of the shaft and actually approaches zero for zero shaft speeds. The thrust load will be carried on a film of oil regardless of shaft rotation for as long as the pump continues to supply the required volume and pressure

Source:

Marks Standard Handbook for Mechanical Engineers

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