Machinery's Handbook, 31st Edition
Thrust Bearings
2419
Q c = required flow per chamfer, gpm Q o c = uncorrected required flow per chamfer, gpm Q F = film flow, gpm s = oil-groove width Δ t = temperature rise, ° F U = velocity, feet per minute V = effective width-to-length ratio for one pad W = applied load, pounds
Y G = oil-flow factor Y L = leakage factor Y S = shape factor Z = viscosity, centipoises α = dimensionless film-thickness factor Δ = taper ξ = kinetic energy correction factor Note: In the following, subscript 1 denotes inside diameter and subscript 2 denotes out side diameter. Subscript i denotes inlet and subscript o denotes outlet. Flat Plate Thrust Bearing Design.— The following steps define the performance of a flat plate thrust bearing, one section of which is shown in Fig. 2. Although each bearing section is wedge shaped, as shown below right, for the purposes of design calculation, it is considered to be a rectangle with a length b equal to the circumferential length along the pitch line of the section being considered, and a width a equal to the difference in the external and internal radii. General Parameters: a) From Table 1, the maximum unit load is between 75 and 100 pounds per square inch; and b) the outside diameter is usually between 1.5 and 2.5 times the inside diameter.
b
a
b
h
D 2
D 1
D 1 + D 2 2
U
Fig. 2. Basic Elements of Flat Plate Thrust Bearing. * 1) Inside diameter, D 1 . Determined by shaft size and clearance. 2) Outside diameter, D 2 . Calculated by the formula D K p W D 4 g 2 1 2 2 1 π = + c m where W = applied load, pounds K g = fraction of circumference occupied by pads; usually 0.8 p = bearing unit load, psi * See footnote on page 2418.
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