Movable pulleys are used frequently and some common examples include weightlifting machines used in modern gyms, construction cranes and elevators. Many are used in very large and complex pieces of industrial machinery, while others are simple portable devices like chain or mining hoists.
All pulleys are simple mechanical devices that have been in use for many centuries, and historians believe humans were using simple static pulleys as far back as 1500 B.C.
There are several examples of movable pulleys that appear frequently in everyday life including:
- Bike hoist pulleys are often used in conjunction with fixed pulleys that are attached to the roof of a bike shed or garage.The movable pulleys may be hooked onto the bike and effectively alter the direction of force, allowing the user to haul the bike upwards by pulling down on the belt.
- Construction cranes combine movable pulleys with powerful machinery to move huge loads safely from one location to another.
- Weightlifting machines use movable pulleys to allow users to alter the height of the pulley as well as the weight they intend to lift so they may isolate individual muscle groups and work out safely.
- The chain hoists commonly used in auto shops are a common variation of the movable pulley as they amplify the force of the user and allow for the movement of loads far beyond the strength of a single worker.