A detailed presentation on the topic "Air braking in heavy commercial vehicles (HCVs)". The ppt contains working and technical details of Air Braking System. Main components like Air Compressor, Reservoir, Unloader Valve, Brake Valve, Brake Chamber, Quick Release Valve and Relay Valve has been explained in details in this ppt.

1. Air Braking in *HCVs
Working and Technical Details
A
Presentation On
*HCV : Heavy Commercial Vehicles
Presented By
Deepak Kumar
Mechanical Engineering
Gandhi Institute for Technological Advancement, Bhubaneswar

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Contents

Introduction

History

Why Air Brakes?

Main Parts of Air Brakes

Working of Air Brakes

Future of Air Brakes

Conclusions

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What is a Brake?
Automobiles mean self propelled vehicles OR the vehicles which generate power
itself to carry passengers and goods from one place to another place.
So, during the journey, it is needed to stop OR to slow down the vehicle by
converting the kinetic energy of the moving vehicle into heat & the device which is
used to do so is known as Brake.

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What is an Air Brake?
Air + Brake = Air Brake?

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So, What is an Air Brake?
It’s a type of brake, in which compressed air is used as a working fluid to press the
piston in order to apply pressure on the brake pad to stop the vehicle.

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History of Air Brakes
The first Air Braking system was made by George Westinghouse in 1869, which
was a triple valve air braking system.
Automobiles began using air brakes from 1908 & the first car to have them was
named as Tincher.
The first vacuum assisted air brake was used on the 1928 Pierce-Arrow.

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Why Air Brakes in HCVs?
Braking in HCV is quite different than that of the braking in small vehicles because
as we know that Kinetic Energy depends upon both mass and speed of the vehicle.
In case of HCVs mass is very high & so the kinetic energy is. It needs very large
braking force to apply the brakes and Air Brakes are suitable for this.
In comparatively smaller vehicles, Hydraulic Braking System is used for braking, in
which , Oil (Brake Oil) is used as a working fluid.

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Why Air Brakes in HCVs?
Air brake systems are much more tolerant to leaks. If there is a leak the governor
reloads the compressor and the reservoirs are refilled.
Air brakes use compressed air, which has high potential energy and compressed
air is more suitable to transmit power over a distance.
Air, however, can leak as much as it wants but there is no shortage of it, so
leakage won’t leave you without brakes. Of course repeated pumping of the brakes
could reduce braking power available.

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Why NOT Hydraulic Brakes in HCVs?
In HCVs, wheel base is very large compared to smaller vehicles, so more brake oil
is needed which will increase the cost.
A small leak of brake oil in hydraulic brakes can cause severe damage.
The brake shoes are liable to get ruined if the brake fluid leaks out.
For parking purpose separate mechanical linkage has to be employed which are
not enough for HCVs.

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Main Parts of an Air Braking System

Air Compressor

Reservoir

Unloader Valve

Brake Valve

Brake Chamber

Quick Release Valve

Relay Valve

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Air Compressor
Air Compressor is a device that converts the power into potential energy by means
of pressurized air. An air compressor forces more and more air into a storage tank
to increase the pressure.
A piston type air compressor is used commonly in the braking system.

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Reservoir
Reservoir stores compressed air at the specified pressure for brake application.
It is made up of steel and a safety valve is provided at the top of the reservoir to
regulate the air pressure.
A drain plug is also provided at the bottom for periodic draining of the reservoir in
order to remove the unwanted oil, moisture etc.

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Unloader Valve
Unloader Valve is mounted between the compressor and the reservoir to control
the pressure of air in the reservoir.

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Brake Valve
It is the control valve which is operated by the brake pedal and controls the
intensity of braking in an air pressure system.
It is located between the reservoir and air lines leading to individual brake
chambers.

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Brake Chamber
The brake chambers convert the energy of the compressed air into mechanical
force and motion necessary to operate the vehicle’s brakes.

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Quick Release Valve
It is employed in the front brake to accelerate the release the of air from the brake
chambers.
It directly releases pressure to the atmosphere rather than through the brake valve.

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Relay Valve
The relay valve speeds up the application and release of air from brake chambers.
It supplies air to the brake chambers directly from the reservoir for quick
application of the brake.

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Layout of Air Braking System

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Working Diagrams of Air Brakes

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Future Advancements in Air Braking
Air Disc Brakes for HCVs and Trailers along with ECBS (Electronic Controlled
Braking System) is to be produced with the promise of high-fade resistance,
superior stopping and remarkable stability over S-Cam systems.
External Wear Indicators are also connected to make inspections simple and
reduce the possibility of rotor damage due to excessively worn linings.

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Conclusion
Air Braking system may be bulky and costly but it has low operational cost and
high performance.
Still there are many advancements and experiments to be done on
the Air Braking System like Air Disk Brakes, Size Reduction, Cost Reduction etc.

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References
 Article “Air brake (road vehicle)” from WikiPedia.org
 Video “Commercial vehicle air brakes” from YouTube.com
 Article “How Air Brakes Work” from Auto.HowStuffWorks.com

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Thank You!

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Any Questions?