What is the structure of a crane pulley?

A pulley system is made up of several fixed pulleys and moving pulleys matched together, which can achieve the purpose of both saving effort and changing the direction of force. In use, how much effort is saved and the way the rope is wound depend on the effect of the pulley system.  

Moving Pulley

The moving pulley is borne by two ropes, that is, each rope bears a fraction of the total weight of the object and the moving pulley. The principle is: when n is an odd number, the rope starts from the moving pulley. When using a moving pulley, there are three sections of rope to bear the weight, and each additional moving pulley adds two sections of rope. For example: if n=5, then two moving pulleys are needed (3+2). When n is an even number, the rope starts from the fixed pulley, and at this time all moving pulleys are only borne by two sections of rope. For example: if n=4, then two moving pulleys are needed (2+2).

Fixed Pulley

A fixed pulley is essentially an equal-arm lever, which neither saves nor wastes effort, but can change the direction of the force. It does not save effort to pull the weight through a fixed pulley. The reading of the spring scale is the same whether it passes through the fixed pulley or not. It can be seen that using a fixed pulley does not save effort but can change the direction of the force. In many cases, changing the direction of the force will bring convenience to the work.  

The principle of the fixed pulley: the fixed pulley is essentially an equal-arm lever, and the power arm L1 and the resistance arm L2 are both equal to the radius of the pulley. According to the lever balance condition, it can also be concluded that the fixed pulley does not save effort.  

Pulley System

Pulley system: a pulley system composed of fixed pulleys and moving pulleys, which can both save effort and change the direction of the force.

How many sections of rope are used to lift an object in a pulley system, and the force used to lift the object is a fraction of the total weight.

Although the use of a pulley system saves effort, it costs distance, and the distance moved by the power is greater than the distance moved by the weight.