Gov′ernor (engine), a device attached to a steam-engine or other motor for keeping the speed of the machine constant within practical limits. As applied to a steam-engine, the object of the governor is to act on the throttle-valve or on the supply of steam to the cylinder, so that the supply of steam is proportional to the load. The common engine-governors depend on balancing the centrifugal force of a revolving mass either against gravity or against the force of a spring. The governor applied to the steam-engine by Watt consists of two heavy balls attached to two inclined arms, which are jointed to an upright spindle so that the balls can move in a vertical plane, thus forming a double conical pendulum. The spindle is geared so as to revolve with a speed proportional to that of the engine, and as the speed of the spindle increases the balls fly out and rise against gravity. For a definite speed the balls have a definite position. Beyond this speed they rise, and below this speed they fall. By suitable links and levers the supply of steam is increased or decreased for lower or higher speeds. In modern high speed engines (speeds over 150) the governor most commonly used is placed inside the fly-wheel. A heavy mass on a lever attached to a spoke of the fly-wheel is held toward the center by a spring, and as the speed increases the spring is stretched and the mass flies out. By suitable mechanism this movement regulates the supply of steam. The demand upon a governor is that, in engines for ordinary service, the speed must not vary more than 2%; and for electric light service not over 1%.
WATT'S ENGINE-GOVERNOR
A HIGH SPEED ENGINE-GOVERNOR