hydraulics

Field of study concerned with utilizing the properties of water and other liquids, in particular the way they flow and transmit pressure, and with the application of these properties in engineering. It applies the principles of hydrostatics and hydrodynamics. The oldest type of hydraulic machine is the hydraulic press, invented by Joseph Bramah in England in 1795. The hydraulic principle of fluid pressure transmitting a small force over a small area in order to produce a larger force over a larger area is commonly used in vehicle braking systems, the forging press, and the hydraulic systems of aircraft and earth-moving machinery.

In a car braking system, a small force is applied at the brake pedal. This force is transmitted over a small area through the brake fluid. The force is transmitted to the master piston and acts over a larger area to produce a larger force. The master piston presses the brake pads against the brake discs to slow the movement of the car wheels. The force produced at the larger piston (2) by the smaller piston (1) can be worked out using the formula: force 1/area 1 = force 2/area 2.

A hydraulic press consists of two liquid-connected pistons in cylinders, one of narrow bore, one of large bore. A force applied to the narrow piston applies a certain pressure (force per unit area) to the liquid, which is transmitted to the larger piston. Because the area of this piston is larger, the force exerted on it is larger. Thus the original force has been magnified, although the smaller piston must move a great distance to move the larger piston only a little.