Pulleys are true engineering marvels, even in their simplest form – a single rope running through a wheel – as they allow a human to lift or more a heavy object easily.
The simplest of pulleys are known as fixed pulleys. These systems are such that the pulley’s wheel is attached to a solid object and can turn but can’t move up or down or in any other way. A fixed pulley is used to lift or lower an object.
Movable pulleys are more advanced than fixed pulleys. They allow the pulley itself to move as needed as the human applies force. The advantage of movable pulleys is that they decrease the amount of force that’s needed to move an object. They also can be set up in a way that uses less space than a fixed pulley.
A system that includes both a fixed and a movable pulley is known as a compound pulley and, depending on how many pulleys are used and the direction of the force applied to them, these types of pulley systems can save even more energy and/or can lift/move even heavier objects.
A swivel eye pulley provides dynamic rotation (the pulley’s block, which holds the pulley wheel, rotates). This type of pulley is a great option when someone needs a bit of rotation when picking up a load. A swivel eye pulley can be mounted on a rod, bolt, shackle, etc. What’s more, the “eye” of a swivel eye pulley can slide over pipes, bolts, rods. They can be used with nylon, fibrous or wire ropes.
A fixed eye pulley is similar to a swivel eye, except the eye itself is fixed on the pulley block: the eye cannot turn or swivel.
The force required to lift or move an object can be lessened considerably by using a double- or triple-pulley system. These systems entail the use of two or three pulley blocks, with the rope running through each of them in order to lift the load. Using two or more pulleys considerably reduces the amount of effort needed to hoist or move the object.