108 FARM MECHANICS 



will work in a well as small as eight inches in diameter, 

 and to a depth of 140 feet. It might be made to work 

 at a greater depth, but it seems hardly practical to 

 do so for the reason that, after allowing for friction in 

 the pipes, 100 pounds of air pressure is necessary to 

 lift water 150 feet. An air tank of considerable size is 

 needed to provide storage for sufficient air to operate 

 the system without attention for several days. Care- 

 ful engineering figures are necessary to account for 

 the different depths of farm wells, and the various 

 amounts of water and power required. For instance : 

 The air tank already contains 1,000 gallons of air at 

 atmospheric pressure then : Forcing 1,000 gallons of 

 atmospheric air into a 1,000-gallon tank will give a 

 working pressure of 15 pounds per square inch ; 2,000 

 gallons, 30 pounds ; 3,000 gallons, 45 pounds, and so on. 

 Therefore, a pressure of 100 pounds in a 1,000-gallon 

 tank (42 inches by 14 feet) would require 6,600 gallons 

 of free atmosphere, in addition to the original 1,000 

 gallons, and the tank would then contain 1,000 gallons 

 of compressed air under a working pressure of 100 

 pounds per square inch. A one cylinder compressor 

 6 inches by 6 inches, operating at a speed of 200 R.P.M. 

 would fill this tank to a working pressure of 100 

 pounds in about 50 minutes. One gallon of air will 

 deliver one gallon of water at the faucet. But the 

 air must have the same pressure as the water, and there 

 must be no friction. Thus, one gallon of air under a 

 working pressure of forty-five pounds, will, theoretic- 

 ally, deliver one gallon of water to a height of 100 feet. 

 But it takes three gallons of free air to make one gal- 

 lon of compressed air at forty-five pounds pressure. 

 If the lift is 100 feet, then 1,000 gallons of air under a 



