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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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