preproom.orgThe online science prep room
You are here: Home > Equipment > Model Hydraulic Brakes

Model Hydraulic Brakes
AKA: Hydraulics


A demo setup to show how hydraulics can be used to control braking of a vehicle.


The basic principle behind the science of hydraulics is fairly simple: Force that is applied at a certain point can be transferred to another point using a liquid that cannot be compressed. One application of hydraulics is its use in braking mechanisms in cars and motorcycles. This equipment simply demonstrates this.

There are many varieties of this equipment on the market, some with single pistons (usually syringes) some with electrically powered wheels, and some using different sized syringes to show how the difference in their size affects the forces involved.

It is fairly simple to make this demo from scratch using three plastic syringes, some flexible plastic tubing, a ‘T’ connector and a flywheel. The flywheel should be mounted on a board so that it can spin freely.

Mount two of the syringes so that when they are extended, they make contact with the flywheel tightly, mountings which allow the syringes to be removed easily are required here so that they can be filled with liquid easily.

Connect some tubing to the two ensuring they are of equal lengths. Connect these to a ‘T’ joint and to another single length of tube. Before connecting the final syringe that acts as the brake ‘pedal’, fill the tubing with water (colouring the water with a small amount of food colouring makes the liquid easier to see) ensuring any bubbles of air are removed. It may take some trial and error to get the amount of liquid correct in the syringes so that when the single syringe is actuated, the other two fill equally. When complete, pressing the single syringe should allow the other two to grip the flywheel firmly, stopping the wheel just as they would in a motor vehicle.

Often in hydraulic applications a principle called Hydraulic Multiplication is used in which the surface areas of the pistons are different from each other. Using this principle, if two pistons are connect to each other, and one piston has ten times the surface area of another, it will move one unit for every ten units the other moves.

Other equipment using the same principles include the hydraulic can crusher and the hydraulic lifting device.


 CautionThe contents of this page are for information only. Please refer to CLEAPSS or ASE safety advice and/or publications before undertaking any preparation, practical experiment or using any equipment featured on this site or any other.