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34 Cards in this Set
- Front
- Back
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What are the three types of braking systems? |
service, parking, emergency
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What must the air brake system include?
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service, parking, emergency brakes. air gauges, low pressure warning device
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A full service brake application must deliver to all brake chambers how much of the air reservoir pressure remaining with the brakes applied?
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90%
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What drives the air compressor?
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the gauging through gears or a V-bet
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How is the air compressor cooled?
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by the engine cooling system or by air
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Where does air/water collect in the air tanks?
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toward the bottom
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What are the three types of drains for air tanks?
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manual, automatic, air drier
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How does a manual drain work for air tanks?
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operated by a quarter turn. must be drained at the end of each day
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How does an automatic drain work for air tanks?
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automatically expelled from the valve (these are equipped with manual drains as well)
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How does the air drier work?
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the water and oil are automatically expelled from the spit valve. this spits out water and air each time the governor cycles
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When you press on the foot valve what two forces push back against your foot?
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spring valve, air pressure
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In a air disc brake instead of a s-cam the brake cam shaft twists what?
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a power screw
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What must all air tanks on air brakes vehicles have located between the air compressor and the first reservoir?
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check valve
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What does the one way check valve do?
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keeps air from going out if the air compressor develops a leak
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At what pressure will spring brakes come on?
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20-45psi
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When applying the brakes the push rod should move less than how many inches on most brakes?
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2
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What is generally the minimum the brake linings should be?
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1/4 inch
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How do you do the static leakage test?
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with a fully charged system turn off the engine, release all brakes, and let the system settle. the air shouldn't drop more than 2 psi over a minute
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How do you do the applied leakage test?
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with a fully charged system turn off the engine, release all brakes, and let the system settle. apply the brake and hold the air shouldn't drop more than 3 psi over a minute
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How do you do the air compressor cut out test?
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with engine running the air compressor must cut out prior to 130psi
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How do you do the air compressor cut in test?
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without the air pressure rising and with the engine on slowly pump the brake pedal to reduce the tank pressure. the compressor needs to come on at no lower than 85 psi
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How do you perform the low pressure warning device test?
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engine on or off but electrical power on either way slowly pump the brake pedal to reduce air pressure. the low air pressure warning device must activate between 55 and 75 psi
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How do you do the spring brake check?
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chock the wheels release all parking brakes and shut off the engine. pump the brake pedal to reduce pressure and make sure the spring brake engages (20 to 45psi)
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At what rate should pressure build up
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engine at normal rpm pressure should build from 85 to 100psi within 45 seconds
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How do you check the service brake?
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wait for normal pressure, release the parking brake, move the vehicle forward slowly (about 5mph) and apply the brakes firmly using the brake pedal. any pulling to one side, unusual feel, or delayed stopping action should be checked
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How do you test the parking brake?
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fasten seatbelt set the parking brake and try to move the vehicle. it shouldn't move
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What is the difference between controlled (squeeze) braking and stab braking?
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controlled braking you don't lock the wheels, stab braking you do
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Air brake lag distance at 55mph on dry pavement adds how many feet?
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32
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At 55mph and under good conditions the stopping distance is over what?
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300ft, longer than a football field
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What do you do if the low air pressure warning signal comes on?
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Stop and safely park as soon as possible
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When do you not use the parking brake when parking?
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if the brakes are very hot,in freezing temps if the brakes are very wet
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If brakes are wet what should you do while driving to heat and dry them?
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use them lightly while driving in a low gear
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The push rod and the adjuster arm should be a little over what when brakes are released and not less than what when brakes are applied?
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90 degrees
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What pressure is the air tank safety relief set at
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150
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