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(also, counterbalance, counterpoise), a weight used for the complete or partial balancing of forces and moments in machines or their parts. The installation of counterweights on rotating parts, such as crankshafts, can eliminate the harmful effects of centrifugal forces originating from off-center masses.
In metalcutting machine tools, hoists, deep-well plunger pumps, and similar machines with vertically or obliquely moving parts, counterweights reduce the drive power. In hoisting cranes, counterweights provide stability; the arm and weight of the crane’s counterweight are selected to balance the moment of the weight of the mechanisms and metal frame together with half of the moment of a rated load. Counterweights are usually made in the form of a set of pig-iron or concrete bars or slabs.