546 Farm Mechanics. 



at the center of the belt, and never cross it or have more 

 than two thicknesses of lacing on the side next to the 

 pulley. Fasten the lacing by running the ends through 

 small holes punched in line with the lace holes where they 

 will be in the right place to serve as lacing holes when 

 the belt needs to be shortened. 



691. Calculating the Length of Belts. To ascertain ap- 

 proximate length of a belt to connect two pulleys measure 

 exact distance between the centers of the two pulley shafts. 

 Then add the circumferences of the two pulleys together, 

 dividing the sum by two; add this sum to twice the dis- 

 tance between the centers of the two shafts and the total 

 is the length of belt required. 



FARM PUMPS. 



There are several forms of devices used in lifting water 

 on the farm, chiefly for the use of the stock and as a water 

 supply for the house ; these are known as suction and force 

 pumps and hydraulic rams. 



692. Suction Pump. The common suction pump consists 

 of a cylinder and piston connected below with a suction 

 pipe, and above with a discharge pipe. At the upper end 

 of the suction pipe, usually in the lower end of the cylin- 

 der, below the piston, there is the suction valve which opens 

 upward by the force of the water but closes with the down 

 stroke of the piston, preventing the return of water to the 

 well. In the piston is a second valve, also opening upward 

 which permits the piston to be forced downward through 

 the water in the cylinder, held th.ere by the suction valve, 

 but which closes the moment the piston begins to rise and 

 thus lifts whatever water is above the valve, at the same 

 time tending to produce a vacuum below the piston into 

 which the pressure of the air on the water of the well 

 lifts the water through the suction pipe and past the suc- 

 tion valve already described, 



