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20" X 20"

20
400. The H.P. is 40.

The following rules will be found more professionally accurate from an engineering standpoint, though the term "horse-power" is not now generally employed.

/To find the Nominal Horse-power/.--For /non-condensing/ engines: Multiply the square of the diameter of the cylinder in inches by 7 and divide the product by 80. For /condensing/ engines: Multiply the square of the diameter of the cylinder in inches by 7 and divide the product by 200.

/To find the Actual Horse-power/ of an engine, multiply the area of the cylinder in square inches by the average effective pressure in pounds per square inch, less 3 lb. per square inch as the frictional allowance, and also by the speed of the piston in feet per minute, dividing the product by 33,000, and the quotient will be the actual horse-power.


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