210 
PROFESSOR O. REYNOLDS ON THE THEORY OF LUBRICATION 
The effect of the temperature on a is owing to the different coefficients of expansion 
of brass and iron. Thus :— 
Or—« 0 =(B'—S') (T—T 0 )R, 
where B' and S' are the respective coefficients of expansion of the bearing and journal. 
These for brass and iron are:— 
B'^0000111 
S'= '0000061, 
therefore putting T — T 0 =Tm (the mean rise of temperature due to friction) 
Ox=a 0 ^l+ ’000005“-Tm^ 
=<x 0 (1+ETto) ..(lid) 
Putting 
E for , 000005~ 
«o 
If, as seems general, a 0 is about ’0005 inch, then with a 4-inch journal 
E=-02 about .. (Ill) 
which is sufficiently large to be important. 
32. The Effect of Speed on the Temperature , 
Putting— 
T 0 the temperature of the surroundings and bath. 
T t the mean temperature of the oil as it is carried out of the film. 
T m the mean rise in temperature of the film due to friction. 
Q the volume of the oil carried through per second. 
D the density. 
S the specific heat, 
H the heat generated. 
the heat lost by conduction, 
cr a coefficient of conduction. 
taking 
heat. 
the inch, lb. and degree Fahr. as units, and 12 J as mechanical equivalent of 
Q= 
5*1 
2 
2Rff/TJ 
H 1 =2BdC , T w 
T _T - 
u 'o— 
H-H 0 
BSQ ‘ 
