FRICTIONAL LOSSES IN INTERNAL COMBUSTION ENGINES. 507 
temperature of the cylinder only was observed as the 
bearings remained at practically the same temperature 
throughout. 
For tests on the engine when fully assembled, the speed 
was attained by driving under gas in the ordinary way. 
After disconnecting the piston, etc., the generator was 
used aS a motor to speed the engine up for the tests, 
though full speed could not quite be reached by this means. 
By auxiliary tests on the generator alone, the friction 
loss in its bearings was determined and deducted from the 
results of the main tests. 
Lastly, exactly similar experiments were made on a 
30-H.P. Crossley Gas Hngine of very much the same type 
as the National,—bore 94", stroke 18” and moment of inertia 
of flywheel, etc., 1070 ft. ib. units. Sight feed drip lubri- 
cation was relied on throughout. 
The engine was arranged to drive a generator by means 
of a leather belt. This generator was used as a motor for 
driving the dismantled engine ina first series of tests made 
immediately after overhauling and reassembling. The 
friction of the main bearings came out extremely high, and 
so another series was made after a month or so of running 
in. In this later series the engine was run up to speed, 
when gas could not be used, by a friction drive from a 
small 3-H.P. electric motor acting directly on to the fly- 
wheel. A hand screw adjusted the friction pressure by 
moving the whole motor on a special sliding base. 
9. Procedure followed in each test.—A somewhat 
detailed description of the work carried out on the National 
Gas engine will serve for the tests on all three engines. 
(a) Twelve runs were made with the engine when fully 
assembled—six of these were at different cylinder 
temperatures to find the effect of temperature on 
the friction of the piston. 
