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 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 [Mark Smith. The Annapolis Book of Seamanship. 1999 Simon & Schuster] .

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). [J. J. Coulton, “Lifting in Early Greek Architecture,” The Journal of Hellenic Studies, Vol. 94. (1974), pp. 1-19 (12)]

The largest electric drive winch in the world is placed on the "Balder", a construction ship.Fact|date=February 2007 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.

ee also

* Steam donkey
* [http://knol.google.com/k/mads-gorm-larsen/boat-winch/fpvu60g9z3k1/2# Article about boat winches ]

References