Air Brakes Flashcards
What is coefficient of friction?
The coefficient of friction is the amount of force required to move an object divided by the weight of the object
Which of the following refers to the amount of time required to stop a vehicle once the brakes have been applied?
Braking time
Result of applying 60 psi air pressure of a type 30 brake chamber?
60 x 30 = 1800 lb of force is produced
Cam operated foundation air brakes are non servo because they are mounted to a fixed pin
Cam operated foundation air brakes are non servo because they are mounted to a fixed pin
What information is provided through the edge code stamped on a brake block?
The friction code of the lining
Why are flat camshafts used on the brake systems of steering axles?
Flat cam shafts improve straight line stability during braking
The slack adjuster multiplies the amount of force created at the pushrod
The slack adjuster multiplies the amount of force created at the pushrod
Air disc brakes use a return spring to release the brake pad
Air disc brakes use a return spring to release the brake pad
Compressors deliver air in the loaded cycle
Compressors deliver air in the loaded cycle
-Inlet valve held open by unloaded piston
-Discharge valve closed
What condition is the conpressor in?
Compressor is unloaded
What is the purpose of the governor?
The governor controls the maximum system pressure in the air brake system
What side of the service brake chamber is always vented to atmospheric air pressure?
The pushrod side of the service brake chamber
Brake chamber size is related to the GVW rating of a vehicle
Brake chamber size is related to the GVW rating of a vehicle
The quick release valve speeds up the release of the steer axle brakes
The quick release valve speeds up the release of the steer axle brakes
Where does the service air pressure present at the inlet port of the quick release valve vent to when the brakes are releasing?
The inlet for pressure vents to atmosphere through the dual brake valve exhaust port
What best describes the purpose of the secondary brake circuit?
The secondary brake circuit is to allow the operator to control the application and release of the steer axle brakes
What best describes “cracking pressure”?
The pressure required to move the relay valve piston down closing the exhaust valve and opening the inlet valve
What best describes the term “differential pressure” in a relay valve?
Differential pressure is the difference between the control pressure and the delivery pressure
What is the material which removes the moisture from the air as it moves through the air dryer?
Dessicant
Air reservoirs must store a volume of air equal to 12 times the combined volume of the brake chambers on the unit.
Air reservoirs must store a volume of air equal to 12 times the combined volume of the brake chambers on the unit.
What is the purpose of the single check valve in the air reservoirs?
The single check valve ensure the system will have pressure in the event of a reservoir pressure loss.
What is the purpose of the safety valve?
The safety valve protects the system from excess pressure in the event of governor failure.
Flexible hose is used near brake chambers to allow for movement
Flexible hose is used near brake chambers to allow for movement
What is true about a dual circuit brake valve
The primary delivery port is open to the exhaust port in the released position
What valve is replaced by the bobtail valve?
The standard relay valve
A vehicle requires 200 hp to accelerate from 0 to 100 kmh in 60 seconds. If the same vehicle is brought to a complete stop in 6 seconds, the braking system must develope:
2000 hp
One advantage that air brake systems have is that:
The system does not have to be bled when connecting or disconnecting trailers like hydraulic braking systems do
If the weight of a vehicle is doubled, the power required to stop the vehicle will:
Be doubled
If the speed of a moving vehicle is doubled, the power required to stop the vehicle will:
Be increased four times
If both the speed and weight of a moving vehicle are doubled, the power required to stop the vehicle will:
Be increased eight times
The term lag time refers to the time required:
For the air system to apply the brakes
The component of the basic air system that allows the operator to regulate brake application pressure is the:
Brake valve
Brake lining edge code identifies the lining by:
The initials of the manufacturer,
The normal coefficient of friction,
The hot coefficient of friction
Using brake lining with a GAWR that is too low can result in:
Brake fade
The caliper of an air disc brake must be able to slide on its mounting pins so the:
Outboard brake pad contacts the brake rotor
When an air brake compressor piston is on its compression stroke, the inlet valve:
Is closed and the discharge valve is open
When the compressor is in its unloaded cycle:
The inlet valves are held open
The governor controls maximum air system pressure by:
Putting the compressor in the unloaded cycle
The automatic drain valve drains moisture and contamination from the reservoir when
Any drop in reservoir pressure
Air brake antifreeze is used in the air brake system to
Prevent moisture in the system from freezing
Single check valves are installed in the inlet line to both the primary and the secondary service reservoirs because they:
Prevent air loss in the event of a failure in the other reservoirs
The function of a safety valve is to
Limit air pressure build up in the event of a governor failure
CMVSS 121 states the minimum pressure at which the low pressure warning devices must warn the operator is:
60 psi
The function of the relay valve in the primary brake circuit is to speed up the:
Application and release of the primary service brakes
During normal brake applications, the secondary piston of the dual-circuit brake valve is applied by:
Primary service air pressure
Air supply for parking/emergency brake operation flows through a double check valve so that the emergency brakes will:
Not apply if either service reservoir air pressure is lost
The function of the park control valve is to provide manual:
And automatic control of all the parking/emergency brakes on the unit
A quick release valve is often used in parking/emergency brake Circuits to provide quick:
Application of the spring brakes
