hersey: laws of lubrication 551 



and decreases with increase in load, leads at once to the con- 

 clusion that carrying power increases when speed increases. 



tin 

 16. Relation of friction to . The results of about 200 inde- 



P 



pendent determinations of the coefficient of friction of sperm, 

 lard, and machine oils at 10 or more drops per minute may be 

 represented by the equation: . 



/= 0.002+ 6800^ (29) 



P 



for values of 10^ between 1 and 40. The average deviation 



of the observed points from this straight line is about 15 per 

 cent. There is no systematic tendency for the points corre- 

 sponding to the respective oils to cluster together. Equation 

 (29), then, is a particular form of the general equation (11a) 

 for approximately complete lubrication. It would be applicable 

 to any completely lubricated bearing loaded in the ordinary 

 manner, which is geometrically similar to the experimental bear- 

 ing in every respect, including the effect of wear. Equation (29) 

 is cited primarily as an experimental verification of the conclusion 

 that in any given bearing with a given oil supply, the coefficient 



of friction depends only on the single variable . 



A shorter series of experiments with cyhnder oil over the inter- 



ulTI 



val from 10^ = 30 to 250 led, with the same degree of approxi- 



P 

 mation, to the equation 



/= 0.015+ 6800^ (30) 



P 



The difference in the constant terms of the two equations is 

 doubtless due to the fact that, with this very heavy oil, the bear- 

 ing did not completely fill itself. If this surmise is correct, we 

 have an illustration of the effect of S in equation (11). 



