Hoist , term that can also be mentioned as polispasto , is a machine formed by two sets of pulleys , one with mobility and another one left fixed . Through this system, it is possible to move or lift a heavy body.
What the hoist allows is to move something by applying a force less than the weight of the object. In this way, these rigs are widely used in factories and industrial facilities to move loads and materials. Hoists are often used, for example, to load and unload what arrives or should be sent through a transport truck.
There are multiple types of hoists, which are chosen according to the load that is planned to move. There are hoists that apply their power through the electricity , others by levers and some, with the manual force . Hoists, on the other hand, can move objects with the help of chains , strings or cables , as the case may be.
In the most advanced installations, hoists can count on arms or be guided by rails that are installed on the ceilings and that allow to move the load throughout the factory or the warehouse.
A factorial hoist It is one that has fixed pulleys and mobile pulleys that share a saddle. In a hoist of this type with four pulleys (two mobile and two fixed), the force that will have to be applied to lift a load will be equivalent to a quarter of the resistance .
The formula of the force of the factorial hoist is equal to the resistance (the weight of the load you want to lift) over 2 for him number of mobile pulleys , all multiplied by the speed of the gravity . For example, if the load is 50 kg and there are four mobile poles, the force F necessary to lift it with a factorial rig equivalent to (50 kg / 2 x 4) x 9.8 meters on squared seconds; The result is 61.25 Newton.
A potential hoist instead, it is formed by a pulley that is fixed to a point of resistance, located at a height higher than that of the object to be lifted, and by one or more pulleys of movable type. It is a simple machine, a concept of physics that is defined as a mechanical device capable of transforming one movement into another, taking advantage of the incoming force to return a different one in displacement length, direction or magnitude.
The main function of the potential hoist is the displacement up or down objects too heavy to be handled exclusively by the force of a person. It should be mentioned that it is also possible to use it to make movements on the horizontal axis.
Through a steel cable, a rope (also called rope or rope) or a chain that hangs from a surface, the fixed pulley is threaded, and another pulley is also held; at one of its ends the force of traction . From the center of the second pulley, which is of the floating type, another cable extends that also clings to the anterior surface. Continuing with this scheme, it is possible to add as many pulleys as necessary, without forgetting that each one causes the weight exerted on the previous one to be reduced by half.
About him axis of the pulley that is located at the end of the so-called pulley train resistance is applied. The formula to calculate the strength of this type of hoist is as follows: the weight P of the load on 2 raised to number n of mobile pulleys which the rig has. The variable to represent the force, in this case, is T .