# Master Cylinder Diagram: Detailed Explanations

If you have driven an automobile, be it a four wheeler or a two wheeler, you must have noticed that you do not need to apply much force on the braking pedal. Just a slight force stops the vehicle running at high speeds. Lets study more about master cylinder in below sections.

## What is a master cylinder?

A master cylinder is a device that converts mechanical force to hydraulic force. A master cylinder finds its application in braking system of automobiles (of all types).

It is an integral part of braking system. It amplifies the force that we apply on braking pedal and with the help of hydraulic fluid it stops the vehicle that is running at very high speeds. Without a master cylinder, it would get very difficult to stop at emergency situations. A hydraulic brake is always better than a mechanical brake due to the emergency stopping advantage.

Image credits: Fred the Oyster
iThe source code of this SVG is validThis vector image was created with Adobe Illustrator., Master cylinder diagramCC BY-SA 4.0

## Types of master cylinder

Master cylinder is classified into two main types. These types are classified solely on the basis of number of cylinders used in the circuit of braking system.

The most common types of master cylinders used in the braking systems are-

• Single circuit master cylinder– The single circuit master cylinder uses only one cylinder in the braking circuit of the braking system. This way the braking force is distributed equally among all the wheels of the automobile. This type of circuit is quite unsafe and should be used only in light weighted four wheeler vehicles, two wheeler vehicles and e-auto rickshaws.
• Tandem or dual circuit master cylinder- In Tandem circuit master cylinder, more than one cylinder is used (generally two). This way the braking system can be used independently in front wheels and rear wheels. This improves the safety feature in the design of braking system.

## Master cylinder diagram

The master cylinder is an assembly of many parts. The main working parts of the master cylinder are shown in the diagram below-

The notable parts shown in the above diagram are- Reservoir, cylinder, piston, valve, spring and braking pedal. We shall study in detail about them in below sections.

## Master cylinder parts

As discussed above, master cylinder is an assembly of many working parts. Let us discuss about the main working parts of the master cylinder-

• Reservoir– Reservoir acts like a storage tank for braking fluid. Braking fluid rests inside the reservoir, when the braking pedal acts then certain amount of braking fluid is taken into the braking circuit.
• Cylinder– Inside the cylinder, piston movement takes place. When the braking fluid exerts pressure, piston movement takes place inside the cylinder.
• Piston– Piston transfers hydraulic force from the hydraulic fluid to the brakes. The application of brakes stops the vehicle running at high speeds. Piston rests inside the cylinder.
• Returning spring– A spring generally stores potential energy inside it when a force is applied on it. This potential energy helps it to regain its original shape back. In a master cylinder, returning spring is used to bring back the piston and braking pedal to their original positions once the braking application is complete.
• Valve– Valve acts like an outlet portion to which the braking line is attached. The compressed braking fluid passes to the caliper through this valve.
• Braking pedal– The braking pedal is a lever on which the driver applies the braking force. Although the force applied by the driver is not equal to the actual force required for stopping the vehicle. The force applied on the pedal is transferred to the hydraulic fluid. This fluid exerts hydraulic force to the brakes. The brakes are actuated by this hydraulic force and so the braking application takes place.

## Single circuit master cylinder working

The following steps take place while a braking force is applied on single circuit master cylinder.

• When no braking force is applied, that is when the pedal is idle. The inlet valve is closed and no braking fluid flows through the circuit.
• When the braking force is applied on the brakes, the inlet valve is opened and the braking fluid flows from the reservoir to the compression chamber.
• When the braking fluid attains enough compression pressure, it flows through the braking lines and moves the brakes. This way the application of brakes takes place.
• The master cylinder amplifies the braking force applied by the driver.
• When the brake pedal is left idle again, the braking fluid returns back to the reservoir.

## Tandem or dual circuit master cylinder working

The working of tandem circuit master cylinder is similar to that of single circuit master cylinder. Let us see about its working in detail below-

• Similar to single circuit master cylinder, the application of braking force on braking pedal activates the primary cylinder or the compression chamber.
• After the first cylinder is activated, the braking fluid flows through another cylinder also called as secondary cylinder. After the secondary cylinder is activated, another circuit also starts participating in braking application.
• This way two cylinders participate in the braking application. This feature can also be used to make independent braking system for front wheel and rear wheel.
• This type of circuit is also safer and is used in almost all four wheeler vehicles.

## Need of a master cylinder

As we have discussed above, master cylinder uses hydraulic force for the application of brakes. Hydraulic force is always better than the mechanical force as it can be used in emergency situations with better efficiency.

The need of a master cylinder arises due to multiple reasons. They are-

• It can allow independent braking systems for front and rear wheels.
• They can be used in emergency situations with better efficiency.
• They amplify the force applied on the braking pedal and make it equal to the actual braking force required to stop the vehicle.
• It decreases the risk of failure because it can be used as independent systems for front and rear wheels.