A steam engine has a steam pressure of 251b. per square inch, the bore of the cylinder being 1 in., the length of the stroke 13/4 in., and the speed 350 revolutions per minute. The maximum effective pressure may be 22 lb. per square inch. The area of the piston is 1 x 1 x .7854 = •7854sq.in., and the length of the stroke is 1 3/4/12= 7/48ft.

Then, if the engine is double-acting, and the steam supply is kept up throughout the stroke, the maximum indicated power will be (22x 7/48 x.7854 x 350 x 2) /33,000=1/20 horse power (say). The maximum brake-power will be less than this - say 1/30 horse-power.