Spraying for the Alfalfa Weevil. +1 
One-cylinder pumps operated by hand are usually rated on the 
basis of 30 strokes per minute, and those driven by power at 50 
strokes per minute. Duplex and triplex pumps are driven at a 
speed of 40 to 50 revolutions per minute, giving, respectively, 80 to 
100 strokes per minute for the former cad 120 to 150 for the latter. 
If it is necessary to estimate the size of pump needed for a given 
kind of work the process is reversed; for example, it has just been 
shown that a 10-nozzle outfit applying 100 gallons per acre and 
traveling 200 feet per minute uses about 9 gallons per minute. To 
maintain this flow a power pump at 50 strokes per minute must de- 
liver 9-50, or 0.18 gallon per stroke. If it is a double-acting pump, 
Ira, 7.—An excellent outfit adapted for aifalfa-weevil spraying by the Colorado Ex- 
periment Station in cooperation with the authors. 
each stroke fills and empties the cylinder twice, and the contents of 
the cylinder must be 0.09 of a gallon or 20.79 cubic inches. The 
area of a 3-inch plunger is 1.5 by 1.5 by 3.1416, or 7.0686 square inches, 
and the length of stroke required to give a capacity of 20.79 cubic 
inches is therefore 20.79~7.0686, or 2.9 inches. A 24-inch cylinder 
would need to have a stroke of about 41 inches. 
A triplex pump operated at 50 revolutions (150 strokes) per min- 
ute would need only one-third the capacity of a single-cylinder pump, 
0.06 gallon. Calculation shows that this can be Ue with a 23- 
inch cylinder >and 24-inch stroke. 
Table I gives the flow per stroke, in fractions of a gallon, of the 
common sizes of double-acting pumps. 
