750 SUCCESSFUL FARMING 



do not work very successfully are used. It is best to average all the 

 speeds of machines and operate a line shaft at a medium speed. 



The Size of Pulleys. — From the following formulas and conditions 

 one may figure the speed or diameter of any given pulley. 



With the speed of the driver, the speed of the driven and the diam- 

 eter of the driver given, the diameter of the driven may be found. 



Example No. 1. 



Diameter of the driver X speed of the driver -p.- , e , . 



— — -£ = Diameter of driven. 



Speed of the driven 



Example No. 2. 



Given the 



Speed of the driven X diameter of the driven t-.- , . , . 



— - — — ; — — — = Diameter ot driver. 



Speed of the driver 



Example No. 3. 

 Given the 



Diameter of the driven X speed of the driven _ o npp j n e j.l p i • 

 Diameter of the driver 



Example No. 4. 

 ( liven the 



Diameter of the driver X speed of the driver <-, , e ,, , • 



— — - — J— - = Speed ot the driven. 



Diameter of the driven 



Kind of Pulleys. — Pulleys on the market at the present time are 

 manufactured from cast iron, steel, wood and paper. Of these, iron is 

 the most commonly used. It is more compact than wood and is cheaper 

 than steel, although wood can stand much higher speed than the average 

 iron pulley of similar size and design. Wooden pulleys have the advantage 

 of holding to a belt better than steel or iron, especially if a belt begins to 

 slip upon the iron pulley, thus wearing its face very smooth. For light 

 work the split pulley, or the pulley which can be divided into two parts, 

 is the most convenient upon the market, especially if machines are changed 

 from time to time for different purposes. 



Straight and Crown Faces. — Iron pulleys are usually made crowning 

 or slightly oval across the face. Where belts do not require shifting, this 

 form holds belts to place in good shape. If the load is not heavy the 

 crown pulley does not weaken the belt to a great extent, but with heavy 

 loads the main strain comes upon the center of the belt and this causes a 

 stretching and often develops splits. 



Covering Steel Pulleys. — If steel pulleys are used and their surface 

 becomes slick to the point where belts slip badly, they may be covered 

 with a leather face. This can be accomplished in the following manner: 



Clean the surface of the pulley with gasoline and apply a coat of 

 varnish upon which a layer of soft paper is placed. Upon this paper a 

 second coat of varnish is applied. A piece of leather belting is cut to fit 

 the diameter of the wheel and while the varnish is still moist the section 



