ON SPHERE AND ROLLER MECHANISM FOR TEANSMITTING POWER. 495 



directly from a motor by means of a pulley (p), the other (h) being driven 

 by friction at their point of contact. The latter disc is connected directly 

 to a dynamometer brake (c), the resistance of which is shown by means 

 of a lever (e) and a rod (/). At the same time the normal pressure at 

 the point of contact (d) is measured by means of a combination of levers 

 (l and k). These levers act thus. A weight (w) being hung upon the 

 end of the lever (l), which has its fulcrum at the top of the support (I), 

 acts by means of a link (h) upon a second lever (A;), which has its fulcrum 

 at the lower end. The lever (k) carries the bearings of the shaft of the 

 disc (6), and thus the weight (w) is an exact measure of the horizontal 

 forces between the discs, the leverage being such as to make this latter 

 just twenty-one times as great as the weight in question. 

 The resistance overcome by the belt was threefold : — 



(a) The brake friction. 



(b) The bearing „ 



(c) The rolling „ 



The first only of these could be accurately determined, the sum of the 

 others berng estimated in the following way. Up to a certain point 

 the belt was powerful enough to overcome all the friction and to make 

 the wheels skid over each other, but beyond that the sum of the resist- 

 ances was suflBcient to make the belt slip, which it did at a fairly constant 

 point. Thus for a definite increase of pressure the increase of (b) and 

 (c) could be determined by the diminished reading of (a). jSy this means 

 the forces transmitted to the driven wheel were approximately estimated. 



Three sets of experiments were made : — 



(i.) Cast-iron discs with flat faces, i^in. wide. 



(ii.) Cast-iron discs with flat faces, y'y in. wide. 



(iii) Chilled cast-iron discs with spherical faces ground true. 



The results of these experiments are given in the following Table III. 



TABLE III. — Eesults of Experiments with Special Apparatus for Testing 

 THE Forces Transmitted by Rolling Contact. 



