Tilting Pad Thrust Plate Bearing Design Equation and Calculator

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Tilting Pad Thrust Plate Bearing Design Equation and Calculator

Machine Design Applications
Bearing Engineering and Design

Tilting Pad Thrust Plate Bearing Design Equation and Calculator:

Each bearing section is wedge shaped, as shown at the right below, 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,

Tilting Pad Thrust Plate Bearing

Basic Element of thrust bearing

Preview: Tapered Land Thrust Plate Bearing Design Calculator

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

Table p

External diameter formula:

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

Where:

W = applied load, pounds
K_g = fraction of circumference occupied by pads; usually, 0.8
p = unit load, see Table p

Radial pad width , given in inches

a = (1/2) ( D₂ - D₁ )

Pitch line circumference , given in inches

B = π (D₁ + D₂ ) / 2

Number of bearing pads, estimated

i = ( B K_g ) / a = nearest even number

i as the nearest even number to that calculated.

Length of bearing pad given in inches

b = ( B K_g ) / i

Operating number

O = ( 1.45 x 10^-7 Z₂ U ) / ( 5 p b z)

Where, Z₂ = viscosity of oil at outlet temperature (inlet temperature assumed temperatur rise through the bearing).

Minimum film thickness given in mils inches - h_min = α b

α = dimensionless film thickness is found from Film Thickness Factor Chart

In general, this value should be 0.001 inch for small bearings and 0.002 inch for larger and high-speed bearings.

Coefficient of friction, f found from Coefficient of Friction Chart

Friction power loss (HP), derived from table using film thickness h

P_f = ( f W U ) / 33,000

Actual oil flow, given in gpm

Q = 0.0591 α i a b U

Δt = ( 0.0217 f p ) / ( α c )

Where:

c = specific heat of oil in Btu/gal/°F

Notation:

a = radial width of pad, inches
b = circumferential length of pad at pitch line, inches
b₂ = 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 = oil-supply 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 = oil-groove width
∆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

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