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Pulley construction principle
Nov 16, 2018

The pulley block is made up of several fixed pulleys and movable pulleys, which can achieve the purpose of saving labor and changing the direction of force action. In use, the labor saving and the winding method of the rope are determined by the use effect of the pulley block. The pulley is carried by two ropes, that is, each rope bears the object and the movable pulley


The force is a fraction of the total weight of the object and the moving pulley.

The principle is that when n is an odd number, the rope driven pulley starts. When using a moving pulley, there are three sections of rope, and each additional one of the moving pulleys adds two pieces of rope. For example: n=5, you need two moving pulleys (3+2). When n is even, the rope starts from the fixed pulley, and all the movable pulleys are only used by two ropes. For example: n=4, you need two moving pulleys (2+2).


Secondly, according to the requirements to determine the number of pulleys, the principle is: the general: two ropes with a moving pulley, a moving pulley is generally equipped with a fixed pulley. When the direction of force action does not require change, the even-numbered section of the rope can be reduced by a fixed pulley; to change the direction of force action, a fixed pulley is required.


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