Brake System is paramount system in any vehicle. One can not imagine driving any sort of vehicle without a brake. This post will discuss in detail about what is a Brake System, it’s various types, how it works and its advantages as well as disadvantages sub system wise.
What is Brake System
A procedure that is used to stop the motion of a vehicle is called Braking system. Usually, brakes use friction between two surfaces to convert the kinetic energy of the vehicle into heat, thereby, stopping the vehicle. It can also be defined as the system which applies artificial resistance to a moving body to reduce or stop the motion of a moving body.
Fig. 1 – Introduction to Brake System
Different techniques are used to achieve the friction required to stop the vehicle. The most important factor that has to be considered while designing any Brake System is to manage the heat energy generated which otherwise would damage the vehicle or the Brake System.
Fig. 2 below shows the representation of forces acting on rotating wheel when Brakes are applied. Braking Force is the Force required by the vehicle to stop or Decelerate when the Brakes are applied.
When the system try to decelerate the vehicle, or tries to reduce the rotation of the wheel, static frictional force or Tangential Force acts on the wheel which reduces the linear speed of the vehicle. This force acts in the opposite direction to the vehicle in motion. There are other forces acting on the vehicle as shown below.
Fig. 2 – Representation of Forces on Rotating Wheel
Types of Brake System
The different types of Braking System include:
- Mechanical Braking System
- Hydraulic Braking System
- Anti-lock Braking System
- Electromagnetic Braking System
Mechanical Brake System
This type of system uses the friction technique to stop a vehicle. Two types of brakes that are commonly used in the mechanical braking system are:
- Drum Brakes
- Disc Brakes
They are usually used as hand brakes or emergency brakes. They are placed at the back of the vehicle and are connected by steel wires to the lever near the driver’s seat. When the driver pulls the handbrake, the Brake shoe holds the drum from moving and hence the vehicle is stopped.
A Disc Brake is connected to the wheels of the vehicles. It is usually made up of cast iron. Brake pads (also called brake calipers) are placed on the disk brakes. To stop the vehicle, friction is applied on both sides of the disc by the Brake pads which causes the kinetic energy to convert into heat energy, and the vehicle stops.
Fig.3 – (a) Disk Brake (b) Drum Brake
Hydraulic Brake System
This system uses brake fluids to transfer the pressure from the control mechanism to the braking mechanism. These fluids usually contain glycol ether or Di-ethylene glycol. One of the most common arrangements of the Hydraulic Braking system consists of the following parts:
- Brake Pedal
- Master Cylinder Assembly
- Brake Caliper Assembly
It is also called as lever. To slow down the speed of the vehicle, the driver/user pushes Brake Pedal.
It is also known as an actuating rod.
Master Cylinder Assembly
Master Cylinder Assembly is made up of one or two pistons, a series of gaskets or O-rings, a return spring and the fluid reservoir.
Brake Caliper Assembly
Brake Caliper Assembly consists of one or two hollow caliper pistons that are made up of aluminum or chrome-plated steel. It also contains a rotor or drum attached to the axle and a set of thermally conductive Brakes.
The brake pedal and the master cylinder are attached by the push-rod. The push-rod exerts a force on the pistons of the master cylinder when the brake pedals are pressed. The fluid in the reservoir flows into a pressure chamber through a compensating pot.
This increases the pressure in the entire braking system and forces the fluid to the calipers. Then the calipers apply this force on the Brake pads, causing the vehicle to slow down or stop.
Fig. 4 – Mechanism of Hydraulic Braking System
Anti-lock Braking System (ABS)
Anti-lock Braking System or ABS is a technology that uses sensors to detect other vehicles or obstacles and prevents them from colliding. The sensors are usually GPS, radar or videos.
Fig. 5 – Anti-lock Braking System
Electromagnetic Braking System
This system uses electromagnetic force to create the resistance required to stop a vehicle. This system works by passing a magnetic flux in a direction perpendicular to the rotating direction of the wheel and then rapid current flows in the direction opposite to the rotation of the wheel, then this opposing force stops the wheel.
The Eddy Current brake is one of the most common applications of the electromagnetic braking system.
Fig. 6 – Eddy Current Brake of Japanese Bullet Train
How Brake System Works
Since most cars have Disc Brakes, let us understand the working principle of Disc Brakes. Single-piston floating caliper is the most common type of Disc Brake used in cars. A car in motion has certain amount of Kinetic Energy and when the User/Driver pushes the brakes through the Brake pedal, the power is amplified by the servo system or Booster and the force is transmitted Hydraulically by the Master Cylinder.
This Hydraulic pressure reaches the brake pads on the wheels through tube filled with brake oil also called brake fluid. Single-piston floating caliper adjusts and centers itself when the Brakes are applied and the pistons in turn push the brake pads on all the four wheels. Brake pads clamp the Rotor as they make slight contact with the Rotor.
Fig. 7 – Working of Disc Brake
The Brake pads are on either side of the Disc and they are not in use when the Brakes are not pushed. The Friction produced reduces the speed of the car. The Brakes convert Kinetic Energy into heat energy and to dissipate this heat, vents are provided between the sides of the Disc to provide cooling. Thus, the vehicle decelerates or slows down and finally stops.
Advantages of Brake System
The advantages of Brake system has been divided into following subgroups for ease of understanding.
Advantages of Drum Brakes include:
- The cost of production and purchase of Drum Brakes are economical.
- Drum Brakes can be used alongside Disc Brakes.
Advantages of Disk Brakes include:
- It provides heat dissipation.
- Unlike the drum brake, the disk brake does not collect water or dust because of its open structure.
Advantages of Hydraulic Brakes are:
- The Hydraulic Brakes wear out less than the mechanical Brakes because of the absence of joints in its construction.
- The frictional loss at high-speed braking is reduced since the brake fluid also acts as a lubricant.
- The Hydraulic Brakes produce less thermal stress compared to Mechanical Braking.
Advantages of Anti-lock Brakes are:
- Since the obstacles can be sensed beforehand, it reduces the possibilities of brake locking up or skidding.
- The Anti-lock Braking system helps to maintain the smooth steering of the vehicle.
Advantages of Electromagnetic Brakes
- Since there is no physical contact required to create friction between the parts, the wear and tear of this system are less than the other system.
- The heat generated by electromagnetic braking is extremely less compared to any other braking.
- Electromagnetic braking is cheaper and almost no maintenance cost is required.
Disadvantages of Brake System
The disadvantages of Brake system has also been divided into following subgroups for ease of understanding.
Disadvantages of Drum Brakes are:
- They have an enclosed structure so it collects water during rain and cannot get rid of it easily. This causes them to work poorly.
- The enclosed system of the Drum Brakes also causes it to heat quicker than the other systems because the amount of air entering inside is limited.
Disadvantages of Disc Brakes include:
- They are not efficient for use during parking because the Brake-pads cannot maintain a smooth rotor surface.
- They are only effective to reduce the speed of the vehicle, but it cannot stop the vehicle as effectively as the Drum Brakes.
Disadvantages of Hydraulic Brakes are:
- If the brake-fluid leak out, then the brake-shoes may be ruined.
- High moisture in the environment can change the quality of the hydraulic fluid and cause corrosion of the internal components.
- If the atmospheric temperature is too high, the heat may boil the fluid into bubbles and the pressure cannot be applied effectively.
Disadvantages of Anti-lock Brakes are:
- The cost of installation and maintenance is very expensive.
- The whole system is delicate compared to the mechanical systems and requires more attention to keep it unharmed.
Disadvantages of Electromagnetic Brakes are:
- Since this system runs on battery, it drains the battery much quicker.
- The brake-shoe takes a long time to come back to its original position because of the residual magnetism.