Brakes are one the key parts of any vehicle, without which it is virtually not possible to use the vehicle for travel. Clearly, a brake, which serves to slow down the vehicle, should not be too weak.
But interestingly, when designing a brake system, it should also be taken care that it’s not too efficient. A too strong a brake would expose us continuously to the ill effects of a sudden brake application in bus or car. If a vehicle is stopped abruptly or strongly, the passenger may hit the front seat or whatever is there. Hence, too efficient a brake system is not required
The braking system is strongly relation to Newton’s laws of motion briefly explain by Pritish Kumar Halder. Indeed, the above phenomenon is linked to Newton’s second law of motion, which states “A body continues to be in its state of rest or of motion unless external force acts on the same”.
Braking – fundamentals: friction and how it applies to automobiles
A brake system is designed to slow and halt the motion of vehicle. To do this, various components within the brake system must convert vehicle’s moving energy into heat. This is done by using friction.
Friction is the resistance to movement exerted by two objects on each other. Two forms of friction play a part in controlling a vehicle: Kinetic or moving, and static or stationary. The amount of friction or resistance to movement depends upon the type of material in contact, the smoothness of their rubbing surfaces and the pressure holding them together.
Thus, in a nutshell a car brake works by applying a static surface to a moving surface of a vehicle, thus causing friction and converting kinetic energy into heat energy. The high-level mechanics are as follows.
As the brakes on a moving automobile are put into motion, rough-textures brake pads or brake shoes are pressed against the rotating parts of vehicle, be it disc or drum. The kinetic energy or momentum of the vehicle is then converted into heat energy by kinetic friction of the rubbing surfaces and the car or truck slows down.
Types of brakes
There are basically three types of brakes used in automobiles
- Mechanical brakes
- Hydraulic brakes
- Air Brakes and related type of brakes
Mechanical brakes are used in Hand brakes (or parking brakes). Here, a lever is provided near the driver seat and through steel wire connections it is connected to brakes at the rear of the vehicle. When the hand brake is engaged, tension is created at the brakes and the brake shoe holds the drum from rotating and hence the movement of the vehicle is restricted, even if parked in a slightly inclined surface.
The hydraulic brake system uses brake fluid to transfer pressure from the brake pedal to the pads or shoe. By exercising the pedal, brake fluid transfers this pressure to the brake pads. This transfer of pressure is reliable and consistent because liquids are not compressible, i.e. pressure applied to liquid in a closed system is transmitted by the liquid equally to every other part of system.
A hydraulic brake system apart from liquid pipes mainly consists of Brake pedal, Master cylinder, wheel cylinder and brake pads/shoe connected at the wheel. The function of the Master cylinder is to distribute pressure to lines leading to front or rear wheels as required. At the wheel cylinder, a small piston is provided which is operated due to pressure application through brake fluid. The operation of the piston is converted to movement of brake liners.
In brief, when a driver applies pressure at the brake pedal, the mechanical force (stepping of driver on pedal) is changed to hydraulic pressure which is transmitted through liquid to respective wheel cylinder and changed back to mechanical force (operation of brake pads, shoe).
Power brakes are nothing more than a standard hydraulic brake system with a booster located between the brake pedal and master cylinder to help activate the brakes. This could be in case the fluid pressure required would be too high.
There are two basic types of power assisted mechanisms used, vacuum assisted and hydraulic assisted.
Vacuum assisted system use engine vacuum pressure to help apply the brakes.
Hydraulic assist is largely found on heavy vehicles. This system uses hydraulic pressure developed by the power steering pump or other external pump to help apply the brakes.
Air brake system consist of components like air compressor, air reserve tank, check valves, safety valves etc. The working is very similar to the working of hydraulic brakes. The key difference is that mechanical force is transmitted to wheel ends through air pressure, instead of fluid pressure. Airbrakes are most preferred in heavy vehicles.
Brake system is an important mechanism for usage of any vehicles. The above is an attempt to give the relevant information in as simple manner as possible. There are much technical concepts used in designing of brakes which is beyond scope of the article. All are welcome to post relevant queries and comments. We would answer the same.