Bicycle Drum Brake

The screeching tires may be one of the most annoying things that you used to hear in the streets. However, for some people, the squeal of tires and violence the smell of brake fluid can mean something totally different: that their brakes are doing their job of keeping passengers safe from a collision.

Brakes are devices that are used to slow rotating wheels until they stop. Friction brakes are the most common examples of these brakes. Brakes as used on motor vehicles every day like, bikes, trucks and trains use friction between the brake pad and wheel to slow the movement of a vehicle.

However, the friction created by the brakes generates much heat. The braking system must be able to dissipate this heat or else the brake could lose its effectiveness.

There are several types of brakes - the most common are those used in automobiles: the disc and drum brakes. Both, however, rely on hydraulics, or the use of brake fluid pressure to activate the brakes.

Drum brakes work by the constriction of brake shoes installed inside the wheel. The friction generated by this action slows the movement of the vehicle.

The disc brake works by clamping the rotors of the wheel itself. Disc brakes are superior to drum brakes due to the fact that disc brakes are not prone to malfunction even when wet or immersed in water. This malfunction is called brake fade. The disc brakes can also handle higher braking temperatures and dissipate heat faster. In addition, disc brakes do not hold water as drum brakes can.

In 1985, the first antilock brake (ABS) was introduced for cars in the United States. ABS is a safety feature to give drivers more control when braking. ABS has a microprocessor and sensors that monitor individual wheel speed brakes in a vehicle. The hydraulic control valves for each brake circuit prevent skidding during panic stops or when braking hard on wet or slippery. In 1990, ABS is available on about 25 percent of all new cars and trucks. Today, ABS is available on more than 90 percent of all new vehicles.

Other brake systems

In 1869, George Westinghouse invented a different system of applying the brakes. Instead of using liquid pressure to apply the brakes, he used a system in which it is the air pressure that prevents the application of the brakes.

This is useful because the Achilles heel of hydraulic brakes is that when there is a loss of pressure, the brakes become ineffective. In the Westinghouse system, when there is loss of air pressure, the brakes will automatically apply.

It is a safer alternative that is useful for transporting heavy loads such as trains.

Large, heavy vehicles and buses and the trains, use compressed air pressure rather than hydraulic fluid to operate their brakes.

Brakes tomorrow

While we have much more based on friction for braking, many technological advances call for new methods of braking.

For example aircraft also use spoilers and flaps to slow its speed in air.

Electric cars and other electric vehicles use drum and disc brakes at the stop, but some vehicles also use magnetic brakes, which create opposing magnetic fields to resist motion. This type of braking is called regenerative braking. This technique takes some of the vehicle's momentum into electric energy. Regenerative braking uses the magnets in the electric motor itself to slow the vehicle. When the driver releases the accelerator pedal, the electric motor changes into a generator, and regain the energy of the car in reverse and turn it into electricity

The transportation becomes faster, safety becomes a major concern. more powerful means for controlling speed are needed, and the development of braking systems is not far.