BELT POWER TRANSMISSION. LXXXVII. 
devices having proved satisfactory, the author has dwelt on the 
construction of the machine at some length. The method of 
reducing the friction of the hydraulic leathers by rotary move- 
ment in a plane normal to the stroke though obvious, is thought 
to be novel, The practical effect being to reduce the internal 
static friction due to the leathers from 26% to less than one per 
cent. Thus at 100 lbs. pressure on a plunger 1-12” diameter the 
friction was 28 Ibs. 
Agreeing with a formula 7 = re where 
F = Total Friction 
P = Total pounds pressure on ram. 
C = a coefficient 0:3 
D = diameter of plunger 
whereas on rotary movement the friction was represented by 
slightly under one pound. 
It will be noted that the friction of this plunger does not agree 
with the coefficient of John Hicks,! estimated at from 0-03 to 0-09 
for leathers under similar circumstances. 
A large number of transmission tests were made at each par- 
ticular tension, and for convenience of comparison the whole were 
reduced from ‘varying speeds to 1000’ per minute by direct pro- 
portion. 
Table shewing the comparative transmission of horse power at 
1000’ per minute. Cast iron pulleys are of contact 180°. 
Double leather belt, 6” wide, cemented only, oak tanned, grain 
side to pulley, dry, and not dressed. Endless. 
ae. gemrap hens bined Horse power. Nearest coeff. 
275 5-2 0°45 
400 76 ” 
490 8-7 ” 
650 12:1 
1 The Engineer, June 1, 1866. 
