Pneumatic braking system | Construction and Working

Pneumatic braking system | Construction and Working

Pneumatic or air braking system in automobile | Construction and working of pneumatic braking system

  • brake which uses air as a working fluid is known as pneumatic brake. The system actuated to apply this phenomenon is know as pneumatic brake system.
  • An pneumatic brake system or a compressed air brake system is a type of friction brake for vehicles in which compressed air pressing on a piston is used to apply the pressure to the brake pad needed to stop the vehicle.

See also : 

Introduction to Automobile Braking System- Types Of Brakes

Construction and working of Air Brake System used in AutomobileOpens in a new tab.

Construction of pneumatic braking system

  • The simplest air brake system consists of
    • An air compressor
    • A brake valve
    • series of brake chambers at the wheels
    • unloader valve
    • A pressure gauge and a safety valve
    • and an air reservoir.
    • These are all connected by tubes.
  • Some air braking systems may have additional components such as
    • stop light switch
    • low pressure indicator
    • An air supply valve to supply air for tyre inflation
    • A quick release air quickly from the front brake chambers when the brake pedal is released
    • limiting valve for limiting the maximum pressure in the front brake chambers and a relay valve to help in quick admission and release of air from the rear brake chambers.
  • working of pneumatic braking system
    working of pneumatic braking system

Working of pneumatic braking system

  • The air compressor operated by the engine forces air at a pressure of 9-10 kscm (kilo standard cubic meters) through the water and oil separator to the air reservoir.
  • The air pressure in the reservoir is indicated by a pressure gauge.
  • The reservoir contains enough compressed air for several braking operations. From the reservoir the air is supplied to the brake valve.
  • As long as brake pedal is not depressed, brake valves stop the passage of air to brake chambers and there is no braking effect.
  • When the brake pedal is depressed, the brake valves varies its position and compressed air is admitted into the wheel brake chambers.
  • In the chambers the air acts upon flexible diaphragms, moves them the pushes out the rods connected with the levers of the brake gear cams.
  • The cams turn and separate the shoes thus braking the wheels.
  • When the brake pedal is released, the supply of compressed air is cut off from the brake chambers and they are connected to the atmosphere.
  • The pressure in the chambers drops, the brake shoes are returned to their initial position and the wheels run free.
  • The brake valve is equipped with a servo mechanism which ensures that the braking force on the shoes is proportional to the force applied to the pedal.
  • Besides the valve imparts a relative reaction to the movement of the pedal so that the driver can sense the degree of brake application.

Sachin Thorat

Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Currently, he is working in the sheet metal industry as a designer. Additionally, he has interested in Product Design, Animation, and Project design. He also likes to write articles related to the mechanical engineering field and tries to motivate other mechanical engineering students by his innovative project ideas, design, models and videos.

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