governor

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governor

machine component

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governor, in technology, device that automatically maintains the rotary speed of an engine or other prime mover within reasonably close limits regardless of the load. A typical governor regulates an engine’s speed by varying the rate at which fuel is furnished to it.

Nearly all governors depend for their action on centrifugal force and consist of a pair of masses rotating about a spindle driven by the prime mover and kept from flying outward by a controlling force, usually applied by springs. With an increase in speed, the controlling force is overcome and the masses move outward; the movement of the masses is transmitted to valves supplying the prime mover with its working fluid or fuel. The revolving masses are balls attached to a vertical spindle by link arms, and the controlling force consists of the weight of the balls. If the load on the engine decreases, the speed will increase, the balls M will move out, and the member C will slide up the vertical spindle and reduce the steam admitted to the engine, thus reducing the speed. An increase in the load will have the opposite effect. Modern governors are used to regulate the flow of gasoline to internal-combustion engines and the flow of steam, water, or gas to various types of turbines. Compare flywheel.

flywheel

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flywheel

machine component

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flywheel, heavy wheel attached to a rotating shaft so as 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. To oppose speed fluctuations effectively, a flywheel is given a high rotational inertia; i.e., most of its weight is well out from the axis. A wheel with a heavy rim connected to the central hub by spokes or a web (wheel A in the Figure) has a high rotational inertia. Many flywheels used on reciprocating engines to smooth out the flow of power are made in this way. The energy stored in a flywheel, however, depends on both the weight distribution and the rotary speed; if the speed is doubled, the kinetic energy is quadrupled. A rim-type flywheel will burst at a much lower rotary speed than a disk-type wheel of the same weight and diameter. For minimum weight and high energy-storing capacity, a flywheel may be made of high-strength steel and designed as a tapered disk, thick at the centre and thin at the rim (see Figure B).

In automobile engines the flywheel serves to smooth out the pulses of energy provided by the combustion in the cylinders and to provide energy for the compression stroke of the pistons. The larger the rotational inertia of the flywheel, the smaller the changes in speed resulting from the intermittent power supply and demand.

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.