Definitions

winch

winch

[winch]
winch, mechanical device for hauling or lifting consisting essentially of a movable drum around which a cable is wound so that rotation of the drum produces a drawing force at the end of the cable. A windlass is essentially the same device as a winch, except that a winch may be power-driven whereas a windlass is usually hand-powered and somewhat less sophisticated. Winches are normally equipped with a ratchet wheel and a pawl to prevent slippage of the load, and brakes that allow a load to be lowered or released at a controlled rate. A hoist is another closely related device, mounted so as to be movable (as in a traveling crane). Winches and hoists are widely used in cargo handling, e.g., in ships, factories, and warehouses, and also function as the power unit in derricks, power cranes, and power shovels. A car puller is a winch with a vertical drum axis, used to position railroad cars in freight yards. Certain military and construction vehicles designed for off-road use are equipped with engine-powered winches that can be used for lifting and hauling or to extricate the vehicle should it become stuck in areas where traction is poor.

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 and attached hand crank. In larger forms, winches stand at the heart of machines as diverse as tow trucks, steam shovels and elevators. The spool can also be called the winch drum. More elaborate designs have gear assemblies and can be powered by electric, hydraulic, pneumatic or internal combustion drives. Some may include a solenoid brake and/or a mechanical brake or ratchet and pawl device that prevents it from unwinding unless the pawl is retracted.

Applications

Besides industrial applications (e.g. in cranes), winches are used for towing cars, boats, or gliders. There are several winches on almost every boat or ship where they are used to pull anchor or mooring lines, halyards, and sheets.

The rope is usually stored on the winch, but a similar machine that does not store the rope is called a capstan. 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. Winches are often embedded in the stage floor and used to move large set pieces on and off.

History

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 B.C. 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 largest electric drive winch in the world is placed on the Balder, a construction ship. It is used as a Mooring Line Deployment Winch with a diameter of 10.5 meter and an SWL (Safe Working Load) of 275 MT.

See also

References

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