Transactions

620 TRANSACTIONS OF THE A.S.M.E. OCTOBER, 1941flow of oil Q, the assumption has been made that Equation [9]is true at constant values of ZNQ/p. Since transformationsfrom one value of the coefficient of friction to another were madeonly for small changes in bearing dimensions, it is felt that errorsdue to this assumption are small.In order to determine the relationship of / and ZNQ/p forthe bearings of various size, curves at constant pressures of 150psi and 600 psi were drawn as shown in Figs. 7 and 8.Hersey4 has shown by means of dimensional analysis thatof / versus ZNQ/p curves, drawn at constant values of p, givestraight lines on log-log paper with Id as the parameter. Thecurves are drawn parallel to each other in order to simplify themathematical derivation of the power-loss formula. Some slightshifting of the actual test curves was necessary to make themparallel.A unit load of 150 psi was selected as the value on which tobase the loss formula, since in turbine and gear work the bearingpressures vary from 50 to 200 psi, and the loss variation with loadwithin this range is not very great. Fig. 9 illustrates the variationat 5000 rpm for loads from 50 to 600 psi for a 6 X 6-in.bearing.andthus removing the requirement for geometrical similarity sofar as the clearance-diameter and length-diameter ratios areconcerned. The tests herein reported also indicate that in additionwhen l/d is constant.This relationship is illustrated in Figs. 7 and 8, in which a family4 “The Theory of Lubrication,” by M . D. Hersey, John W iley &Sons, Inc., New York, N. Y., 1938, pp. 86, 87, and 88.F ig . 11 B e a r i n g L o s s V e r s u s S p e e d f o r O v e r s h o t L u b r i c a t i o n ;1 2 0 -D e g B e a r i n g s(p = 150 psi; Z ~ 13 centipoises.)F ig . 9K i l o w a t t - L o s s V e r s u s P r e s s u r e C u r v e s(Z — 13 centipoises; 6 X 6-in. bearing.)F io . 12 K i l o w a t t L o s s V e r s u s L e n g t h(Z 13 centipoises; V = 150 psi; speed, 5000 rpm.)