Flywheel

in machinery, a wheel employed to regulate the rate of motion. It is attached usually to a principal shaft, and turns with it. Within reason, the greater the diameter of a flywheel and the heavier its rim, the greater its influence is. The value depends on inertia. The wheel gets under way slowly and loses motion slowly. In the case of a power saw, for instance, a heavy flywheel, once under way, preserves the motion of the saw from being checked by a temporary obstruction, such as a knot or other difficulty. Then, too, when the saw becomes empty, the flywheel prevents its attaining an excessive rate of speed before another log can be brought into place. It is a reservoir in which extra energy, that is to say, motion, is stored to be drawn upon in time of need.