542 hersey: laws of lubrication 



These examples suffice to show the order of accuracy of the 

 different methods and also to indicate the variety of problems 

 to which the formulae are applicable. At best, however, these 

 methods are of limited application, although in special cases 

 they render good service. 



TECHNICAL PHYSICS.— T/ie laws of lubrication of hori- 

 zontal journal hearings. M. D. Hersey, Bureau of Stand- 

 ards. Communicated by E. Buckingham. 



I. relation of laws of lubrication to bearing design 



1. The two laws of lubrication needed in designing. In the 

 design of horizontal journal bearings, after all questions of 

 strength and rigidity have been disposed of, there usually re- 

 mains a question as to length and diameter, which must be settled 

 by reference to the laws of lubrication. Evidently too short a 

 bearing is in danger of abrasion, while too long a bearing entails 

 needless dissipation of power. 



Let the '"coefficient of friction," /, be defined by the equation 



/ = - (1) 



in which F is the frictional resisting force and L the load on the 

 bearing perpendicular to its axis. Let the ''bearing pressure," 

 p, be defined by the equation 



in which I is the length of the bearing and D the diameter of the 

 journal. Let po denote the "carrying power" or greatest per- 

 missible bearing pressure. Then the shortest permissible length 

 of a bearing, ^o, may be calculated from the equation 



'/o = ^.- (3) 



D Po 



while the power dissipated in this bearing at a speed of n revo- 

 lutions per imit time will be 



P = T .Dn .L .f (4) 



