2IO 



SCIENCE 



[VuL. XIV. No 347 



TRANSMISSION OF POWER. belt is loose. It is in this feature that it differs from all other fric- 



There is a new device for the transmission of power before the tions, and bases its claims for superiority, 



public which is attracting a great deal of attention. It consists in We illustrate one application of this principle to the driving of 



running a loose belt between two pulleys instead of the usual way dynamos directly from the fly-wheels of an engine. A great sav- 





FIG. 



■DYNAMOS DRIVEN BY MEANS OF EVANS FRICTION BELT. 



of encircling the pulleys with a belt. Simple as this arrangement 

 is, it is a very efficient method by which power can be transmitted 

 from one shaft to another. The most remarkable thing about it is 



FIG. 2. — PRINCIPLE OF THE EVANS FRICTION BELT. 



the fact that more power can be transmitted in this way, with less 

 pressure on the bearings, than in th§ old way. This may seem at 

 first sight to be unreasonable, but it can be fully demonstrated 

 that this is a fact. It is said that this is owing to the fact that the 



ing in belting, room, and an appreciable saving in power, are 

 among the advantages of this system, and an unusually steady light 

 is produced. 



The arrangement of this system is shown in Fig. 2, where C is 

 a driving-pulley, which drives pulley D, through the medium of the 

 belt. The friction of pulley C on the belt produces a tangential 

 force in the direction of rotation. In a similar way, there will be a 

 corresponding force acting in the opposite direction on the under 

 side of the belt, due to the resistance of the driven pulley. These 

 two forces constitute a static couple. The belt is free to act un- 

 der its influence, and two things take place. The tendency to rota- 

 tion will cause the pressure to be transmitted in an oblique direc- 

 tion, as shown. These two forces will also produce an upsetting 

 or fulling action, which will thicken the belt, and create pressure 

 enough to drive, after a slight pressure is first put on the belt. 



Practical men will appreciate at once the advantage of having a 

 simple and durable way in which they can start and stop one or 

 more dynamos independently of each other, and this without slow- 

 ing down the engine. This system has been in continual use in 

 stations for some time, and has given universal satisfaction ; and 

 large plants which are being built in the vicinity of Boston are pre- 

 paring to adopt this arrangement. 



The same principle is applied by the inventors to the transmis- 

 sion of power from one cone to another, for the purpose of obtain- 

 ing a variable speed. They have also attached a governor to the 

 driven cone in special cases, where a steady speed is required from 

 a source that is variable, and a very close regulation has been thus 

 obtained. This is especially valuable for driving dynamos where 

 water-power is used. 



The patents which control these principles are owned by the 

 Evans Friction Cone Company of Boston. The results of tests 

 which they have made are very interesting. The method seems to 

 be almost universally applicable to all places where power is used. 



