1886.] 



On the Theory of Lubrication. 



201 



plete, and preclude the application of the theory without further 

 integrations. 



The theory has, therefore, been tested by experiments throughout 

 the extreme range of circumstances to which the particular integra- 

 tions undertaken are applicable, and the results, which in many cases 

 check one another, are consistent throughout. 



The agreement of the experimental results with the particular 

 equations obtained on the assumption that the brass as well as 

 the journal are truly circular, must be attributed to the same 

 causes as the great regularity presented by the experimental results 

 themselves. 



Fundamental amongst these causes is, as Mr. Tower has pointed 

 out, the perfect supply of lubricant obtained with the oil-bath. But 

 nearly as important must have been the truth with which the brasses 

 were first fitted to the journal, the smallness of the subsequent wear 

 and the variety of the conditions as to magnitude of load, speed, and 

 direction of motion. 



That a brass in continuous use should preserve a circular section 

 with a constant radius requires either that there should be no wear at 

 all, or that the wear at any point P should be proportional to 

 sin (90°-POH). 



Experience shows that there is wear in ordinary practice, and even 

 in Mr. Tower's experiments, there seems to have been some wear. In 

 these experiments, however, there is every reason to suppose that the 

 wear would have been approximately proportional to c sin (0 O — 0) = 

 c sin (90° — POH), because this represents the approach of the brass 

 to the journal within the mean distance a, for all points except those 

 at which it is negative, at these there would be either no wear at all or 

 a slight positive wear. So long, then, as the journal ran in one direc- 

 tion only, the wea~ would tend to preserve the radius and true circular 

 form of that portion of the arc from A to F (fig. 1, note *), altering 

 the radius at F, and enlarging it from F to B. On reversal, however, 

 A and F change sides, and hence alternate motion in both directions 

 would preserve the radius constant all over the brass. 



The experience emphasised by Mr. Tower, that the journal, after 

 running for some time in one direction, would not run at first in the 

 other, strongly bears out this conclusion. Hence it follows that had 

 the journal been continuously run in one direction, the condition of 

 lubrication, as shown by the distribution of oil pressure round the 

 journal, would have been modified, the pressure falling between and 

 B on the on side of the journal, a conclusion which is borne out by the 

 fact that in the experiments with brass No. 2, which was run for some 

 time continuously in one direction, the pressure measured on the on 

 side is somewhat below that calculated on the assumption of circular 

 form, although the agreement is close for the other four points. 



