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Working principle analysis of crane pulley block
Sep 27, 2018

Working principle of crane pulley block: when n is odd, the rope starts from the movable pulley, and is borne by three pieces of rope when one movable pulley is used, and then each additional piece of rope is added after that.

If n is equal to 5, you need two movable pulleys (3+2).

When N is an even number, the rope starts from the fixed pulley. At this time, all the movable pulley is borne by only two pieces of rope. For example, N =4, two movable pulley (2+2) is needed to determine the fixed pulley number as required.

When the direction of force action is not required to be changed, an fixed pulley can be reduced by an even length rope. To change the direction of force action, a fixed pulley needs to be added.


Through the above explanation, the operating principle of crane pulley block can be summarized as: odd and even constant;

Move must match, even minus must, change to add must.


Crane pulley block


A simple machine consisting of a flexible cable that rotates a grooved disk around a central axis and a transnational disk that rotates around a central axis.

Pulley is lever deformation, belong to lever class simple machine.

In China as early as the warring states period in the book on pulley.

The fixed pulley of the center shaft is called fixed pulley. It is the equal-arm lever of common people.


In practice, a certain number of movable pulleys and fixed pulleys are often combined into various types of pulley groups.

Crane pulley block can not only save effort but also change the direction of force.


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