HOW PULLEYS CHANGED THE WORLD
While the exact origins of the pulley system are not known, it is believed that by 1500 BC some of the first pulley systems were being utilized for hoisting water in Mesopotamia. Although modern technology and pulley systems have changed dramatically, the unmistakable value of a pulley system remains unchanged.
The use of multiple pulleys to create a block and tackle system was first documented by the Greek mathematician and inventor Archimedes. However, it is very likely that primitive block and tackle systems were used unknown centuries earlier during the construction of Stonehenge.
Today, a common example of a pulley in modern equipment is a crane. The first recorded cranes appeared in Greece around the late 6th century BC, and now cranes are an indispensable piece of machinery used for lifting or moving extremely large or heavy objects.
The pulley system works by creating a mechanical advantage for the user relative to the number and orientation of pulleys in the system. The tradeoff for the force gained is distance: a pulley system with higher mechanical advantage will require more rope to move the object the same distance. For example, lets compare two pulley systems: one offers a 2:1 mechanical advantage while the other offers a 4:1 mechanical advantage. To lift a 100kg load a distance of 1 meter, the 2:1 pulley system will require 50KG of force and 2 meters of rope. Alternatively, the 4:1 pulley system will require 25KG of force and 4 meters of rope. In block and tackle systems, the mechanical advantage is also sometimes referred to as purchase.
There are three basic types of pulleys:
- Fixed axle: A mechanical advantage of 1
- Movable axle: A mechanical advantage of 2
- Compound: A combination of fixed and movable pulleys, the mechanical advantage equals the number of pulleys used.
Ronstan produces a wide range of pulleys in different sizes, materials, and configurations creating hundreds of possible compound pulley systems that can be tailored to nearly any application. How have pulley systems made your life easier? Take a look around and you will notice them on clotheslines, airplanes, and everything in between.