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27 terms

Air brakes study guide

STUDY
PLAY
Modern air brake system combine three different systems. The systems are the service, parking and ________ brake systems
Emergency
The driver must be able to see a warning before air pressure in the service tanks fall below ______ PSI
60
The brake pedal in the air brake system:
Controls the air pressure applied to the brakes
Air braking takes more time the hydraulic braking because air:
Takes more time to flow through the lines of than hydraulic fluid
If your vehicle has an alcoholic evaporator, it is there to:
Reduce the risk of ice in the air brake vales in cold weather
If your truck has dual parking control valves, you can use pressure from a separate tank to:
Release the spring emergency parking brakes to move a short distance
To check the free play of manual slack adjusters on S-cam brakes,you should park on:
Level ground, chock the wheels, and turn off the parking brake
Of the choices below, The first thing to do when a low air pressure warning come on is:
Stop and safely as soon as possible
Your vehicle has a dual air brake system If a low air pressure warning comes on for the Secondary system, you should:
Bring the vehicle to a safe stop and continue only when the system is fixed
During normal driving, spring brakes are usually held back by
air pressure
in air brake vehicles, the parking brakes should be used to
any time the vehicle is parked
emergency stab braking is when you
brake as hard as you can, release the brake when the wheels lock,then put on the brakes again when the wheels start rolling
a straight truck air brake system should not leat at a rate of more then ____ PSI per minute with the engine off and the brakes released
2
the air loss rate for a straight truck with the engine off and the brakes on should not be more than
3 psi in one minute
the supply pressure gauge shows how much pressure
is in the air tanks
the brake system that applies and released the brakes when the driver uses the brake pedal is the ________ brake system
service
why should you drain water from the compressed air tanks
water can freeze in cold weather and cause brake failure
total stopping distance for air brakes is longer than that for hydraulic brakes due to
brake lag
the most common type of foundation brake found on heavy vehicles is the
S-cam drum brake
if the compressor develops a leak, that keep the airs in the tanks?
the one-way check valve
Wedge Brakes are
the brake chamber push rod pushes a wedge directly between the ends of two brake shoes. This shoves them apart and against the inside of the brake drum.
Disc Brakes are
In air-operated disc brakes, air pressure acts on a brake chamber and slack adjuster, like s-cam brakes
Spring Brakes are
For parking and emergency braking purposes, a spring brake chamber can be used in conjunction with the standard air chamber.
Slack Adjusters are 1st function
Perform two functions: acts as a lever arm to convert the linear pushrod force to rotational camshaft torque
Slack Adjusters are 2nd function
(2) Allows a simple external adjustment of the lining to drum clearance to compensate for shoe lining wear.
The S-cams rotate
the torque applied by the slack adjusters, resulting in spreading the brake shoes which applies the braking force to the drum
The air brake shoes
Final link in the braking systemare supported by pins inserted into the brake spider, and rollers that contact the S-cam surface.