FARM MOTORS 



325 



Fig. 207. Spur gear- 

 ing. The pinion or 

 small gear to the 

 right is "shrouded." 



feet, but are more expensive. Gears with parallel shafts 

 are called spur gears; those with shafts at 

 an angle are bevel gears. 



Gears transmit power positively, as 

 there is no slippage. A small gear wheel 

 in mesh with a large one is often spoken of 

 as a pinion. 



Friction Gearing. Friction gearing 

 transmits power by the friction of two surfaces in contact. 

 The face of the driven pulley is usually of cast-iron, and that 

 of the driver is of paper or rawhide. Fric- 

 tion gearing is often used where the slip- 

 page is desirable to prevent breakage or to 

 start heavy loads. 



Shafting. Power may be transmitted 

 from one point to another by means of 

 a round shaft, to which pulleys, sprock- 

 ets, or sheaves may be attached. This 

 Fig. 208. Bevei shafting is usually supported 

 by hangers carrying bearings. 

 Collars or rings are attached to the shaft to 

 keep it in place. The supporting hangers 

 should be near the pulleys, or at such short 

 intervals as to prevent excessive vibration of 

 the shafting while running. Usually the hang- 

 ers are placed from six to eight feet apart. 

 The power which the shafting will transmit 

 depends upon the material and the revolutions 

 per minute, and varies directly with the third 

 power of its diameter. 



A common formula for the horsepower of the shafting is : 



D 3 R 



Fig. 209. Worm 

 gearing. 



H. P. 



50 



