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Heavy wheel attached to a rotating shaft to smooth out delivery of power from a motor to a machine. The inertia of the flywheel opposes and moderates fluctuations in the speed of the engine and stores the excess energy for intermittent use. In automobile engines, the flywheel smooths out the pulses of energy provided by the combustion in the cylinders and provides energy for the compression stroke of the pistons. In power presses the actual punching, shearing, and forming are done in only a fraction of the operating cycle. During the longer, nonactive period, the speed of the flywheel is built up slowly by a comparatively low-powered motor. When the press is operating, most of the required energy is provided by the flywheel.
This entry comes from Encyclopædia Britannica Concise. For the full entry on flywheel, visit Britannica.com.