Machinery's Handbook, 31st Edition
2428 Thrust Bearings 12) Minimum film thickness, h. Using the value of K just determined and the selected taper values δ 1 and δ 2 , h is found from Fig. 9. In general, h should be 0.001 inch for small bearings and 0.002 inch for larger and high-speed bearings. 13) Friction power loss, P f . Using the film thickness h , the coefficient J can be obtained from Fig. 10. The friction loss in horsepower is then calculated from the formula . P iabJU Z 87910 f 13 2 = − 14) Required oil flow, Q. May be estimated in gallons per minute for a given temperature rise Δ t from the formula . Q c t P 424 f ∆ = where c = specific heat of the oil in Btu/gal/ ° F Note: A Δ t of 50 ° F is an acceptable maximum. 15) Shape factor, Y s . Needed to compute the actual oil flow and calculated from 1 Y D D ab 8 S 2 2 = − 16) Oil flow factor, Y G . Found from Fig. 11 using Y s and D 1 / D 2 . 17) Actual oil film flow, Q F . The amount of oil in gallons per minute that the bearing film will pass is calculated from the formula . Q D D i D NY Y 8910 F G S 2 1 4 2 2 3 2 δ = − − 2 18) If the flow is insufficient, the tapers can be increased or chamfers calculated to pro vide adequate flow, as in Steps 12–15 of the flat plate thrust bearing design procedure. Example: Design a tapered land thrust bearing for 70,000 pounds at 3600 rpm. The shaft diameter is 6.5 inches. The oil inlet temperature is 110 ° F at 20 psi.
Figures on Curves Are Radial Width of Lands, a , in inches
3
2
1
0.75
0
0
1
2 3 Length of Land, b , inches 4
5
6
Fig. 8. Leakage Factor, Y L , versus Pad Dimensions a and b —Tapered Land Thrust Bearings.* * See footnote on page 2418.
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online