Capstan (nautical)

A capstan is a specialized rotating machine used to multiply pulling force. It features a vertical axle, which is a central rod that spins upright. Sailors use these machines to haul heavy ropes, cables, and hawsers. They can also lift a spar into position on a mast. Capstans help transfer cargo between a ship and a dock. They are also used to fasten a ship to a quay. This mechanical advantage makes heavy labor much more manageable for a crew.

The mechanism of a capstan has changed significantly over time. In its earliest form, the device was a single timber mounted vertically. This timber was free to rotate within the vessel's structure. Sailors inserted long levers, known as bars, into holes at the top. By pushing these bars, they caused the timber to turn. A rope was wrapped several turns around the drum to provide grip. A rudimentary ratchet was often included to hold the tension. This ensured the rope would not slip backward.

As technology progressed, capstans evolved into more complex designs. Later models consisted of a wooden drum mounted on an iron axle. Some designs featured two barrels on a single common axle. This allowed men on two different decks to apply force simultaneously. Eventually, capstans were constructed entirely of iron. These iron versions used gearing in the head to provide mechanical advantage. When sailors pushed the bars counterclockwise, the gears helped the work. Some capstans were even connected to an anchor windlass on the deck below.

The history of the capstan is tied to maritime exploration. The word likely entered the English language during the 14th century. It may have arrived via Portuguese or Spanish shipmen during the Crusades. The term connects to Old French and Old Provençal words meaning "pulley cord." It also traces back to the Latin word for a halter. Many historians consider both the device and its name to be Spanish inventions. This highlights the long history of nautical engineering in the Mediterranean and Atlantic regions.

Industrial advancements brought new power sources to these machines. In the 19th century, steam-powered capstan winches became available. These offered a massive saving in human effort. A compact steam engine and boiler were placed below the decks. A shaft then drove the winch from underneath. In 1883, Ruston, Proctor and Company marketed a specific design for fishing vessels. This helped sailing trawlers fetch in heavy nets after a trawl.

Sometimes, the size of an anchor required a special solution. As ships grew, anchor chains became too large for the capstan. A wet or heavy chain was also difficult to manage directly. To solve this, sailors used a messenger. A messenger is a continuous loop of cable or chain. It wraps around the capstan to act as an intermediate device. The main anchor cable attaches to the messenger using ropes called nippers. This allows for a continuous hoist of the anchor without stopping.

Modern capstans operate using various types of power. They can be driven electrically, hydraulically, or pneumatically. They may also use an internal combustion engine. Most modern versions use a gearbox to manage power. The gearbox trades reduced speed for increased torque, which is rotational force. This allows the machine to pull much heavier loads than a simple motor could alone.

Capstans are not limited to the ocean. On land, hydraulic capstans were used in railway goods yards for shunting. At the Broad Street goods station in London, they moved railcars. The deck there was too weak to support a heavy locomotive. Therefore, ropes and capstans were used instead. You can even find this principle in small electronics. Magnetic tape devices, like cassette players, use a small capstan. It draws the tape across the tape head using the same basic principle found at sea.