Advantages of using pulleys in cranes and selection of materials for pulley manufacturing

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The winding system of a crane consists of pulleys, drums, and steel wires. Pulleys are one of the very important components in a crane; their absence or improper operation can accelerate the wear of the steel wires, eventually leading to the wires coming out of their grooves or the hook falling off, thus causing accidents. Based on the rotation mode and function of the pulley’s central axis, we can classify pulleys into movable and fixed pulleys. The difference between them is that the shaft of a fixed pulley remains fixed and cannot move; it is used to change the direction of the steel cable and increase speed, but it does not save effort ； The shaft of the movable pulley can move, which helps to save effort, but it does not increase speed. Additionally, cranes can also use pulleys or pulley blocks to change the direction of rotation of the steel wire rope, and balance pulleys can be used to equalize the tension. Based on the manufacturing material of the pulleys, they can be classified into cast iron pulleys, cast steel pulleys, welded pulleys, as well as plastic and aluminum alloy pulleys. When the operating mechanism is of light or medium capacity, the pulley material is generally made of gray cast iron or ductile cast iron ； This material causes less wear on steel ropes, but it has relatively low strength and poor toughness. When the working mechanism is at a higher level, cast steel pulleys are selected. When the pulley diameter is large and casting it proves difficult, using a welded pulley can reduce its weight.