198 



Prof. 0. Reynolds. 



[Feb. 11, 



same fit. It would be extremely interesting to find bow far under 

 continuous running prolonged wear tends to preserve tbis fit. 

 Mr. Tower's experiments afford only sligbt indication of tbis. It 

 does appear, bowever, tbat tbe brass expanded witb an increase of 

 temperature, and tbat its radius increases as tbe load increases in a 

 very definite manner. 



Anotber circumstance brougbt out by tbis theory, and remarked 

 on botb by Lord Rayleigh and tbe autbor at Montreal, but not before 

 suspected is, tbat tbe point of nearest approach of tbe journal to tbe 

 brass is not by any means in tbe line of load, and what is still 

 more contrary to common supposition, it is on tbe off* side of this 

 line. 



Tbis point H moves as tbe ratio of load to velocity increases ; 

 when tbis ratio is zero, tbe point H coincides witb 0, then as tbe 

 load increases it moves away to the left, till it reaches a maximum 



distance Jw— o , being nearly — ^. The load is still small, smaller 



Li 



than anything in Mr. Tower's experiments, even with the highest 

 velocities. For further increase of load, H returns towards 0, or 

 \ir— 0o increases witb the largest loads and smallest velocities to 

 which the theory has been applied ; this angle is about 40°. With 

 a fairly loaded journal well lubricated it would thus seem that the 

 point of nearest approach of brass to journal, i.e., tbe centre of wear, 

 would be about the middle of the oif side of the brass. 



This circumstance, the reason of which is rendered perfectly clear by 

 the conditions of equilibrium, at once explains a singular phenomenon, 

 incidentally pointed out by Mr. Tower, viz., that the journal having 

 been run in one direction for some time, and carrying its load without 

 heating, on being reversed began to heat again, and this after 

 many repetitions always heating on reversal, although eventually 

 this tendency nearly disappeared. Mr. Tower's suggested explanation 

 appears to the author as too hypothetical to be satisfactory, even in 

 default of any other ; and particularly as this is an effect which would 

 necessarily follow in accordance with the theory, so long as there is 

 wear. For the centre of wear, being on the off side of the line of loads, 

 this wear will tend to preserve or diminish the radius of the brass 

 on the of side, and enlarge it on the on side, a change which will, if 

 anything, improve tbe condition for producing oil pressure while 

 running in this direction, but which will damage the condition on 

 which the production of pressure in the film depends when the journal 

 is reversed and the late off side becomes the new on side. That with 

 a well-worn surface there should be sufficient wear to produce this 



* On and off sides are used by Mr. Tower to express respectively the sides of 

 approach and recession, as B and A, fig. 1, p. 194, the arrow indicating the direction 

 of motion. 



