What is a pulley block?
Blocks are simple devices that consist of a grooved wheel through which a rope or cable can run and change the direction of the force needed to lift a load thus increasing the mechanical advantage.
Blocks are also known as pulleys, the differences between them are blurred in that they are often constructed from similar parts and materials and would seem to have the same purpose. However, although both redirect the force required to lift a load, they are called blocks when constructed with one or more sheaves between each side plate and are capable of handling shock loads, for example should a heavy log fall from a tree being felled, a block would be capable of holding the load until it was brought under control, whereas pulleys, more likely to be running on ball bearings, are used to simply improve mechanical advantage. They are not designed to handle shock loading, they are lighter and smaller than blocks and are usually designed to work with soft ropes rather than cables or wire ropes.
Where blocks are used
Blocks are used wherever there is a need to lift or move a heavy load. The uses are numerous and include lifting gear in the construction industry; vehicle breakdown gear; leisure activities such as mountain chairlifts and hoisting yacht sails; bed hoists for the infirm and disabled; safety lifting gear; mountain or water rescue gear; suspension bridges; industrial safety equipment.
Typical industry sectors
Mainly because of the mechanical advantage feature, i.e. the ratio of the force produced by a device that acts on a load to the applied effort needed to lift or move the load, blocks and tackle are an indispensable piece of equipment and used in almost all sectors of industry – agriculture, commercial, construction, manufacturing, logging, oil drilling and marine.
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