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Step Thrust Plate Bearing Design Equation and Calculator
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Step Thrust Plate Bearing
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Thrust Bearing Typical Loads


Surface

Loads
Lbs/in^{2} 
Max Loads
Lbs/in^{2} 
Parallel surface

< 75

< 150

Step Surface

200

500

Tapered Land Surface

200

500

Tilting Pad Surface

200

500

Reproduced with permission from Wilcock and Booser, Bearing Design and Applications, McGrawHill Book Co., Copyright © 1957.
General Design Parameters: Recommended optimum proportions, a = b, b2 = 1.2b1, and e = 0.7h.
External diameter formula:
D_{2} = ( ( 4 W ) / ( ( π K_{g} p ) + D_{1}^{2} )^{1/2}
Where:
W = applied load, pounds
K_{g} = fraction of circumference occupied by pads; usually, 0.8
p = bearing unit load, psi
Radial pad width, given in inches
a = (1/2) ( D_{2} + D_{1} )
Number of bearing pads, i. Assume that the oil groove width, s = 0.062 inch is minimum
i = B / ( a + s ) = nearest even number
i as the nearest even number to that calculated.
Length of bearing pad given in inches
b = B / i  s
Pitch line velocity, given in fpm
U = ( B N ) / 12
where, N  rpm
Film thickness, given in inches
h = [ ( 2.09 x 10^{9} i a ^{3} U Z ) / W ]^{0.5}
Depth of step, given in inches
e = 0.7 h
Friction power loss, given in HP
P_{f} = ( 7.35 x 10^{13} i a^{2} U^{2} Z ) / h
Pad step length, distance is on the pitch line, from the leading edge of the pad to the step. Given in inches.
b_{2} = ( 1.2 b ) / 2.2
Hydrodynamic oil flow, given in gpm
Q = 6.65 x 10^{4} i a h U
Temperature rise, given in degrees F
Δt = ( 42.4 P_{f} ) / ( c Q )
Should temperature rise to be excessive, this is an indication that the flow is insufficient
Notation:
a = radial width of pad, inches
b = circumferential length of pad at pitch line, inches
b_{2} = pad step length
B = circumference of pitch circle, inches
c = specific heat of oil, Btu/gal/°F
D = diameter, inches
e = depth of step, inch
f = coefficient of friction
g = depth of 45° chamfer, inches
h = film thickness, inch
i = number of pads
J = power loss coefficient
K = film thickness factor
K_{g} = fraction of circumference occupied by the pads; usually, 0.8
l = length of chamfer, inches
M = horsepower per square inch
N = revolutions per minute
O = operating number
p = bearing unit load, psi
p_{s} = oilsupply pressure, psi
P_{f} = friction horsepower
Q = total flow, gpm
Q_{c} = required flow per chamfer, gpm
Q^{o}_{c} = uncorrected required flow per chamfer, gpm
Q_{F} = film flow, gpm
s = oilgroove width
∆t = temperature rise, °F
U = velocity, feet per minute
V = effective widthtolength ratio for one pad
W = applied load, pounds
Y_{g} = oilflow factor
Y_{l} = leakage factor
Y_{S} = shape factor
Z = viscosity, centipoises
α = dimensionless filmthickness factor
δ = taper
ξ = kinetic energy correction factor
References:
 Machinery's Handbook, 29th Edition
 Understanding Journal Bearings, Malcolm E. Leader, P.E. Applied Machinery Dynamics Co.
 Theory and Practice of Lubrication for Engineers by Dudley D. Fuller, Wiley and Sons, 1984, ISBN 0 471047031
 Bearing Design and Application by Donald F. Wilcock and E. Richard Booser, McGraw Hill, 1957, 195, LC number 569641
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