Winch

A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the tension of a rope or wire rope (also called 'cable' or 'wire cable'). In its simplest form, it consists of a spool (or drum) attached to a hand crank. Winches are the basis of such machines as tow trucks, steam shovels and elevators. More complex designs have gear assemblies and can be powered by electric, hydraulic, pneumatic or internal combustion drives. It might include a solenoid brake and/or a mechanical brake or ratchet and pawl which prevents it unwinding unless the pawl is retracted. A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the tension of a rope or wire rope (also called 'cable' or 'wire cable'). In its simplest form, it consists of a spool (or drum) attached to a hand crank. Winches are the basis of such machines as tow trucks, steam shovels and elevators. More complex designs have gear assemblies and can be powered by electric, hydraulic, pneumatic or internal combustion drives. It might include a solenoid brake and/or a mechanical brake or ratchet and pawl which prevents it unwinding unless the pawl is retracted. The earliest literary reference to a winch can be found in the account of Herodotus of Halicarnassus on the Persian Wars (Histories 7.36), where he describes how wooden winches were used to tighten the cables for a pontoon bridge across the Hellespont in 480 BC. Winches may have been employed even earlier in Assyria. By the 4th century BC, winch and pulley hoists were regarded by Aristotle as common for architectural use (Mech. 18; 853b10-13). The yacht Reliance, American defender of the 1903 America's Cup, was the first racing boat to be fitted with modern winches below decks, in an era when her competitors relied on pulley systems (block and tackle). The rope may be stored on the winch. When trimming a line on a sailboat, the crew member turns the winch handle with one hand, while tailing (pulling on the loose tail end) with the other to maintain tension on the turns. Some winches have a 'stripper' or cleat to maintain tension. These are known as 'self-tailing' winches. Winches are frequently used as elements of backstage mechanics to move scenery in large theatrical productions. They are often embedded in the stage floor and used to move large set pieces on and off. Off-road vehicles often carry a winch which may be electrically or hydraulically powered, and is wound with a wire cable. If the vehicle loses traction, the winch is used to pull it back to firmer ground.