hersey: laws of lubrication 549 



or for the actual permanent running temperature t getting 



t = r-\-h{tx-r) (1 + VH- kn') (24) 



in which the constant k is given by the relation 



^-^'•|i'--0' (25) 



t J/l l\ c 



11. An approximate expression for the coefficient of friction. 

 From (23) and (21), writing / for /„ approximately 



/=-^'---'^7 ^ .) (26) 



c p [l-^Vl + hrJ ^ ^ 



The coefficient of friction therefore increases less rapidly than 

 the speed, this falling off being more pronounced the larger the 

 value of the heating constant k. 



12. An approximate expression for carrying power. Similarly 

 substituting from (23) into (14) 



Carrying power therefore increases less rapidly than speed, ap- 

 proaching asymptotically the limiting value 



. X 2 



(Po)ma^ = Wp'^^^^ C28) 



IV. EXPERIMENTS 



13. Purpose. The writer made a series of experiments on 

 friction and carrying power at the Massachusetts Institute of 

 Technology in 1909. Their purpose was to determine the 

 influence of viscosity, oil-supply, and other factors on friction, 

 and to test experimentally the notion that carrying power may 

 increase with speed. 



14- Apparatus. The journal was of hardened steel running 

 in a brass bearing 3 inches long by 1 inch in diameter, the radial 

 clearance having been 0.002 inch when the bearing was new. 

 Film thickness variations were studied electrically by measuring 



