A capstan is a machine that is used on sailing ships to pull ropes and cables (also called hawsers). It has a vertical axle, and is very much like the windlass, which has a horizontal axle.
Grip on power pull capstan and it's opposite brakeforce on bollard posts; both work thru Capstan Equation
Man powered capstan is a 2nd Class Lever concentrating man force inwards to smaller radius for more power from levers.
Motor powered capstan spins motor shaft from inside post/not outside levers so is a 3rd Class Lever delivering force wider radius than motor shaft force input.
A model showing what a capstan looks like. The man to left is 'tailing' rope with enough friction to grip turning capstan. Each man's lever is concentrating his larger force radius into the smaller capstan post radius for more power. Levers were removable. Output force used for anchor and sail etc.
Ship side old school man powered capstan power pull (missing levers). Bollard posts for brakeforce hold.
Harbor side man powered capstan with levers removed. Given plenty of turning room to crank levers. Also space in wall to serve pulling rope out to ship drawing towards pier.
Navy sailors tailing motor driven capstan still used on US Nimitz 2005. Once again capstan for power pull, and contrasting bollard post for anti-pull of brakeforce.
Images for kids
Modern tourists turn a capstan. Sailors would coordinate the rhythm of their movements by singing a particular type of sea shanty as they walked around the capstan. The tensioned portion of the rope would hoist a foresail and could also be used to lift a heavy spar into position on the mast or to transfer cargo to or from a dock or lighter.
Below the capstan shown above is the anchor windlass
Diagram of Ruston Proctor Steam Capstan 1883
In Spanish: Cabrestante para niños