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Step Thrust Plate Bearing Design Equation and Calculator

Step Thrust Plate Bearing Design Equation and Calculator:

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Flat Thrust Plate Bearing Design Formulas and Calculator

Step Thrust Plate Bearing

 Thrust Bearing Typical Loads Surface Loads Lbs/in2 Max Loads Lbs/in2 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, McGraw-Hill Book Co., Copyright © 1957.

General Design Parameters: Recommended optimum proportions, a = b, b2 = 1.2b1, and e = 0.7h.

External diameter formula:

D2 = ( ( 4 W ) / ( ( π Kg p ) + D12 )1/2

Where:

Kg = fraction of circumference occupied by pads; usually, 0.8
p = bearing unit load, psi

a = (1/2) ( D2 + D1 )

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

Pf = ( 7.35 x 10-13 i a2 U2 Z ) / h

Pad step length, distance is on the pitch line, from the leading edge of the pad to the step. Given in inches.

b2 = ( 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 Pf ) / ( c Q )

Should temperature rise to be excessive, this is an indication that the flow is insufficient

Notation:

b = circumferential length of pad at pitch line, inches
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
J = power loss coefficient
K = film thickness factor
Kg = 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
ps = oil-supply pressure, psi
Pf = friction horsepower
Q = total flow, gpm
Qc = required flow per chamfer, gpm
Qoc = uncorrected required flow per chamfer, gpm
QF = film flow, gpm
s = oil-groove width
∆t = temperature rise, °F
U = velocity, feet per minute
V = effective width-to-length ratio for one pad
Yg = oil-flow factor
Yl = leakage factor
YS = shape factor
Z = viscosity, centipoises
α = dimensionless film-thickness 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- 471-04703-1
• Bearing Design and Application by Donald F. Wilcock and E. Richard Booser, McGraw Hill, 1957, 195, LC number 56-9641