capstans

Capstans are mechanical devices used to apply pulling power to lines, ropes, or cables on ships and in industry. A capstan is a cylindrical drum mounted on a vertical axis on the deck; rope or hawser is wound around the drum. The drum is rotated by crew using long bars inserted into sockets in the capstan head, or by powered drives such as electric, hydraulic, or steam motors. A brake or pawl mechanism prevents backward motion under load, allowing the operator to hold or steadily increase tension.

In operation, lines are wrapped around the capstan and hauled by rotating the drum; workers apply force with capstan bars, often in watches, to tighten mooring lines, tow lines, or rigging. Capstans are common on ships, in shipyards, and in industrial settings. They are well suited for handling multiple lines and providing controlled, incremental force. They differ from a windlass, which typically has a horizontal drum and is used mainly for anchors and chain, though modern vessels may deploy both for different tasks. Modern capstans may include integrated controls, variable-speed drives, brakes, and safety interlocks.

Historically, capstans appear in ancient and medieval seafaring and were gradually mechanized with electric or steam power in the 19th and 20th centuries. They remain a standard component of mooring equipment and heavy-lift systems.