- 498 E. P. TAYLOR. 
perature, etc., and also how frictional resistance at the 
rubbing surfaces varied with the same factors. 
The object of the present paper is to summarise the 
results of a series of experiments carried out on several 
internal combustion engines to determine the distribution 
of frictional losses in such engines under specified conditions; 
and further to describe certain useful modifications of 
methods and apparatus arrived at in the course of the 
investigation. 
2. The Retardation Method.—To determine the distri- 
bution of friction in an engine the most convenient way, 
and, at the same time, one by which most accurate results 
can be obtained, is that known as the retardation method 
of determining engine friction. 
This method was employed in the separation of friction 
losses in three engines at the P. N. Russell School of 
Engineering. The method is so generally known that only 
a brief description is necessary. When an engine is run 
up to speed, energy is stored up in the revolving masses. 
On removing the source of power the speed will gradually 
diminish owing to dissipation of the energy by a retarding 
torque set up by friction in the different sections of the 
machine. 
The magnitude of this retarding torque can be deter- 
mined when the negative acceleration and moment of 
inertia of the revolving masses are known. 
Expressed algebraically 
T; = Lo 2a 
where T; = friction torque in Ibs. ft. 4 
I = moment of inertia in ibs. ft. units. 
© = retardation in radians per sec. per sec. 
n = retardation in revolutions per sec. per sec. 
