Pulley systems consist of one or more grooved wheels, and a rope or a belt. Pulleys form a type of a simple machine, and are used to pull heavy loads to high locations. Applications include hoisting sails on boats, lifting loads from a well, and hauling up loads using cranes or trucks. In studying pulley systems, students can design simple projects that will demonstrate how pulley systems work.
Single Block and Tackle Pulley System
A block and tackle is one form of a pulley system which can be designed with two pulley wheels as its "blocks" and a rope passed through the wheels' grooves as the "tackle." The pulley wheels can be made of wooden or plastic material then outfitted with an axle. One wheel will be designated on the upper block of the pulley system, and the other one on the lower block. The rope is fastened on the upper wheel's axle, and then is wove around the lower wheel before it goes up to pass through the upper wheel and to the pulling force. The lower block will carry the load to be lifted. Using this project, students can experiment and measure how much force is required to lift the loads. This project design should result in a lifting force of about half of the load.
Double Tandem Pulley System
Students can create a variation of the single block and tackle system above and see which variation works more efficiently. One variation can be designed to form a double tandem pulley system. The lower and upper block of this system utilises two wheels each. The two wheels are fixed one on top of the other on the same axle. Like the single block and tackle, the rope is fastened on the upper axle then wove around the first wheel of the lower block. The rope goes to the second wheel of the upper block, and then to the second wheel of the lower block before going up finally to the first wheel of the upper block and to the pulling force. The load is placed on a hook built on the lower block.
Elevator Pulley System
A simple elevator pulley system can be made by using five wheels and a wooden rectangular frame with a stand. The three wheels will be attached to the top of the wooden frame, and the other two wheels will be secured to a thin wooden slab where the load will also be suspended. A rope is woven around the first wheel on the top of the frame then goes down to the first wheel secured on the slab, goes up to the second wheel on the top frame, goes down to the second wheel on the slab before finally weaving through the third wheel on top and to the pulling force.
Different loads can be suspended on the hook of the wooden slab, and a scale is used to measure the pulling force. Students record the measurements and represent the outcome in a graph. This design should result to a lifting force of about a quarter of the load.
Pulley Motor Car
Pulley systems can also be incorporated with a motor to design a pulley motor car. The motor creates the mechanical energy or the force that is transferred to the wheels of the car by the pulley system. Aside from the motor and the pulley system, this project also demonstrates a wheel and axle machine. The wheel and axle is made up of the rotating wheel of the car and the fixed shaft of the motor.