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For the tool used to raise paddle gear on canal locks, see Windlass ("lock key")
Differential windlass

A windlass is an apparatus for moving heavy weights. Typically, a windlass consists of a horizontal cylinder (barrel), which is rotated by the turn of a crank or belt. A winch is affixed to one or both ends, and a cable or rope is wound around the winch, pulling a weight attached to the opposite end.

Windlasses are sometimes used on boats to raise the anchor as an alternative to a vertical capstan (see anchor windlass).

Windlasses can also be used to raise water from a well. The oldest description of a well windlass, a rotating wooden rod installed across the mouth of a well, is found in Isidore of Seville's (c. 560–636) Origenes (XX, 15, 1-3).[1] In the Late Middle Ages European crossbows employed a windlass as a cocking mechanism. In the Dark Ages the windlass was also used to raise stones during the construction of cathedrals.

Differential windlass

In a differential windlass, also called a Chinese windlass,[2][3][4] there are two coaxial drums of different diameters r and r'. The rope is wound onto one drum while it unwinds from the other, with a movable pulley hanging in the bight between the drums. Since each turn of the crank raises the pulley and attached weight by only <math>2\pi(r - r')</math>, very large mechanical advantages can be obtained.

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  1. Oleson, John Peter (1984), Greek and Roman Mechanical Water-lifting Devices. The History of a Technology, Dordrecht: D. Reidel, pp. 56f., ISBN 90-277-1693-5 
  2. Template:OED
  3. Morris, Christopher, ed. (1992), Academic Press Dictionary of Science and Technology, Gulf Professional Publishing, p. 416, ISBN 9780122004001 
  4. Knight, Edward H. (1884), The Practical Dictionary of Mechanics, Cassell, Petter, Galpin & Co  "Chinese-windlass, a differential windlass in which the cord winds off one part of the barrel and on to the other."

nl:Windas cs:Rumpál