the piston exerts the maximum of turning power. In Fig. 20 each crank is at 45° with the horizontal, and both pistons are able to do work. The power of one piston is constantly increasing while that of the other is decreasing. If single -action cylinders are used, at least three of these are needed to produce a perpetual turning movement, independently of a fly-wheel.
THE FUNCTION OF THE FLY-WHEEL.
A fly-wheel acts