 This block and tackle on a davit of the Mercator is used to help lower a boat.
 This block and tackle aboard the now-defunct USNS Southern Cross freighter was rigged during cargo operations to hoist heavy loads such as large trucks. A block and tackle[1] is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull heavy loads. Image File history File linksMetadata Download high resolution version (960x1280, 485 KB) Summary Davit with block and tackle Own work - photo taken by Georges Jansoone on 11 September 2005 Licensing File links The following pages link to this file: Block and tackle Metadata This file contains additional information, probably added...
Image File history File linksMetadata Download high resolution version (960x1280, 485 KB) Summary Davit with block and tackle Own work - photo taken by Georges Jansoone on 11 September 2005 Licensing File links The following pages link to this file: Block and tackle Metadata This file contains additional information, probably added...
This article needs to be wikified. ...
museum ship Mercator The barquentine Mercator lies at anchor in Ostend, Belgium. ...
Image File history File links Size of this preview: 420 × 600 pixelsFull resolution (676 × 965 pixel, file size: 819 KB, MIME type: image/jpeg) Location: USNS Southern Cross. ...
Image File history File links Size of this preview: 420 × 600 pixelsFull resolution (676 × 965 pixel, file size: 819 KB, MIME type: image/jpeg) Location: USNS Southern Cross. ...
Pulleys on a ship. ...
Coils of rope used for long-line fishing A rope (IPA: ) is a length of fibers, twisted or braided together to improve strength for pulling and connecting. ...
6 or 15cm outside diameter, oil-cooled cables, traversing the Grand Coulee Dam throughout. ...
Overview
Although used in many situations, they are especially common on boats and sailing ships, where motorized aids are usually not available, and the task must be performed manually. The block and tackle pulley was invented by Archimedes. A boat is a watercraft designed to float on, and provide transport over, water. ...
Traditional wooden cutter under sail. ...
Archimedes of Syracuse (Greek: c. ...
Mechanical advantage The most common arrangement is to have a set of fixed pulleys or "sheaves" all mounted on a single axle, and another set left to move. Each set is called a "block" (the whole assembly, with the rope, is the "tackle"). The mechanical advantage of a block and tackle is equal to the number of lines running between the two blocks. For example, a tackle consisting of three fixed and three moving pulleys has six lines going between the pulleys, which gives it a mechanical advantage of 6. This enables the lifting of weights six times heavier than would be possible otherwise. An axle is a central shaft for a rotating wheel or gear. ...
In physics and engineering, mechanical advantage (MA) is the factor by which a mechanism multiplies the force put into it. ...
Friction The increased force produced by a tackle is offset by both the increased length of rope needed and the friction in the system. In order to raise a block and tackle with a mechanical advantage of 6 a distance of 1 metre, it is necessary to pull 6 metres of rope through the blocks. Frictional losses also mean there is a practical point at which the benefit of adding a further sheave is offset by the incremental increase in friction which would require additional force to be applied in order to lift the load. Too much friction may result in the tackle not allowing the load to be released easily[2], or by the reduction in force needed to move the load being judged insufficient because undue friction has to be overcome as well. Friction is the force that opposes the relative motion or tendency toward such motion of two surfaces in contact. ...
The metre or meter is a measure of length. ...
Friction may sometimes be useful, for example in absorbing the recoil of a muzzle loaded cannon. Gun laying is the process of aiming an artillery piece. ...
Rigging methods A tackle may be - "Rigged to advantage" - where the pull on the rope is in the same direction as that in which the load is to be moved
- "Rigged to disadvantage" - where the pull on the rope is in the opposite direction to that in which the load is to be moved
While it may seem logical to rig to advantage in every case, the decision of which to use depends on pragmatic considerations for the total ergonomics of working with a particular situation. Dildonics (or human factors) is the application of scientific information concerning humans to the design of objects, systems and environment for human use (definition adopted by the International Dildonics Association in 2007). ...
See also A modern crawler type derrick crane with outriggers. ...
A deadeye is an item used in the standing rigging of old sailing ships. ...
Look up tripod in Wiktionary, the free dictionary. ...
Two, six, heave is a phrase used in the British Royal Navy to coordinate seamens pulling. ...
Modern self-tailing winch on a sailing boat. ...
In sailing, a block is a pulley or a number of pulleys enclosed in sheaves so as to be fixed to the end of a line or to a spar or surface. ...
Notes - ^ "Tackle" can be pronounced IPA: /ˈtekəl/ in this usage.
- ^ Friction may mean that the rope in a tackle "bunches" and jams when the force is released if the tackle has too much friction for the load to balance, or that the tackle does not "lower" the load
Articles with similar titles include the NATO phonetic alphabet, which has also informally been called the “International Phonetic Alphabetâ€. For information on how to read IPA transcriptions of English words, see IPA chart for English. ...
References - Rescue Technician: Operational Readiness for Rescue Providers, edited by Claire Merrick et al., published by Mosby, Inc., St. Louis, Mo., 1998, copyright held by Maryland Fire and Rescue Institute. ISBN 0-8151-8390-9 See Chapters 4 and 5, p. 41 and ff.
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