182 
PROFESSOR O. REYNOLDS ON THE THEORY OF LUBRICATION 
H continues to recede as the load increases. But when HC becomes greater than 
IIP 2 , the pressure between P 2 and C would become negative if the condition did not 
break down by discontinuity in the oil, which is sure to occur when the pressure falls 
below that of zero, and then the condition becomes the same as that with a limited 
supply of oil. 
This is important, as it shows that with extreme loads the oil bath comes to be 
practically the same as that of a limited supply of oil, and hence that the extreme 
load which the brass would carry would be the same in both cases—as Mr. Tower has 
shown it to be. 
In all Mr. Tower’s experiments with the oil bath it appears that the conditions 
were such that IT was in retreat as the load increased from C towards 0, and that, 
except in the extreme cases, P 3 had not come up to C. 
Figs. 2, 3, 4 (Plate 8), show the exact curves of pressure as calculated by the exact 
method to be given, for circumstances corresponding very closely with one of Mr. 
Tower’s experiments, in which he actually measured the pressure of oil at three 
points in the film. These measured pressures are shown by the crosses. 
The result of the calculations for this experiment is to show, what could not indeed 
be measured, that in Mr. Tower’s experiment the difference in the radii of the brass 
and journal at 70°, and a load of 100 lbs. per square inch, 
4 a — -00077 
GH= -000375 
(The angle) OJH=48° 
18. The Wear and Heating of Bearings. 
Before the journal starts the effect of the load will have brought the brass into 
contact with the journal at O. At starting the surfaces will be in contact, and the 
initial friction will be between solid surfaces, causing some abrasion. 
After motion commences the surfaces gradually separate as the velocity increases, 
more particularly in the case of the oil bath, in which case at starting the friction will 
be much the same as with a limited supply of oil. 
As the speed increases according to the load, GH approaches, according to the 
supply of oil, to a, and varies but slightly with any further increase of speed; so that 
the resistance becomes more nearly proportional to the speed and less affected by the 
load. 
When the condition of steady lubrication has been .attained, if the surfaces are 
completely separated by oil there should be no wear. But if there is wear, as it 
appears from one cause or another there generally is, it would take place most rapidly 
where the surfaces are nearest : that is, at GH on the off side of O. 
Thus while the motion is in one direction the tendency to wear the surfaces to a fit 
would be confined to the off side of O. 
