Parts of a Hydraulic Brake
The hydraulic brake system, better known as the disc brake system, is a mechanical miracle that many people take for granted every day in mo...
The hydraulic brake system, better known as the disc brake system, is a mechanical miracle that many people take for granted every day in modern transportation. In fact, it was not that long ago that the brake system for cars, buses and motorbikes used the drum brake, pads of asbestos or some anti-inflammatory substance pressed hard against the wheel drum to stop it via friction. Instead, the hydraulic brake system, using the power of fluid pressure, is a major leap forward compared to the sloppy stopping power of the drum brake.
The Basic Concept
Similar to the drum brake, the hydraulic brake uses pressure and friction to slow a vehicle down. However, unlike the drum brake, the mechanisms are far more precise, require less manual application, and are more reliable with added new features, such as anti-lock and anti-skid.
The typical hydraulic brake system uses a setup that involves a control unit, a reservoir for the brake fluid, tubing for the fluid to travel through, calipers which apply the pressure, and rotors which are discs attached to the vehicle wheels that receive the brake pressure. The system is commonly used on motorcycles and scooters, cars and expensive mountain bicycles.
The Control Unit and Brake Line
The hydraulic brake design has the control unit situation either as a foot brake pedal in a car or a hand lever on a motorcycle. This control unit is connected to a system that is entirely filled with brake fluid. No air is allowed because it degrades the brake fluid, usually glycol-ether based, and it reduces the hydraulic pressure effect that the fluid creates. Removal of air from the line is called "bleeding the brakes" since it drains the air until only oil comes out of the drain point. Then the fluid line is sealed and ready to use. The line is also reinforced with steel braid to make sure that it does not burst or warp under pressure.
The Fluid and Storage
Fluid not needed in the line is kept in a reservoir unit which draws down fluid temporarily as more pressure is needed. This happens due to a vacuum created when the control unit sends fluid down the line to create pressure at the brake unit itself. The vacuum then draws fluid behind it to maintain pressure. When the control unit releases pressure, the extra fluid flows back to the reservoir.
The Stopping Parts
In the brake unit, at the other end of the brake line, is the brake stopping system. Generally this involves the caliper unit and the rotor. The rotor is the easier to describe of the two. It is a metal disc attached to a wheel by being bolted onto the wheel hub. This way the disc spins at the same rate of speed as the wheel. When pressure is applied, the disc slows down and due to the connection slows the wheel down as well.
The caliper partially slips over the rotor like almost like a half doughnut in many cases. It covers the rotor disc on both of its flat sides. When fluid pressure is applied, pistons inside the caliper respond and press onto heat-resistant brake pads that apply against the rotor spinning in between the caliper. This slows down the rotor. When pressure is released, the pistons and pads retract and the wheel spins freely again.
Improved Performance
The amount of pressure created with fluid trapped in a tight space is exponentially greater than that of the drum brake system, so the performance of the hydraulic brake is superior. It also takes little pressure from the control unit to create the significant stopping power, thus is more convenient and accurate in performance. It is no surprise that the hydraulic brake system has become the standard stopping power in vehicles over the drum brake system today.
