Air Brakes

Question 1

What is coefficient of friction?

Answer 1

The coefficient of friction is the amount of force required to move an object divided by the weight of the object

Question 2

Which of the following refers to the amount of time required to stop a vehicle once the brakes have been applied?

Answer 2

Braking time

Question 3

Result of applying 60 psi air pressure of a type 30 brake chamber?

Answer 3

60 x 30 = 1800 lb of force is produced

Question 4

Cam operated foundation air brakes are non servo because they are mounted to a fixed pin

Answer 4

Cam operated foundation air brakes are non servo because they are mounted to a fixed pin

Question 5

What information is provided through the edge code stamped on a brake block?

Answer 5

The friction code of the lining

Question 6

Why are flat camshafts used on the brake systems of steering axles?

Answer 6

Flat cam shafts improve straight line stability during braking

Question 7

The slack adjuster multiplies the amount of force created at the pushrod

Answer 7

The slack adjuster multiplies the amount of force created at the pushrod

Question 8

Air disc brakes use a return spring to release the brake pad

Answer 8

Air disc brakes use a return spring to release the brake pad

Question 9

Compressors deliver air in the loaded cycle

Answer 9

Compressors deliver air in the loaded cycle

Question 10

-Inlet valve held open by unloaded piston
-Discharge valve closed

What condition is the conpressor in?

Answer 10

Compressor is unloaded

Question 11

What is the purpose of the governor?

Answer 11

The governor controls the maximum system pressure in the air brake system

Question 12

What side of the service brake chamber is always vented to atmospheric air pressure?

Answer 12

The pushrod side of the service brake chamber

Question 13

Brake chamber size is related to the GVW rating of a vehicle

Answer 13

Brake chamber size is related to the GVW rating of a vehicle

Question 14

The quick release valve speeds up the release of the steer axle brakes

Answer 14

The quick release valve speeds up the release of the steer axle brakes

Question 15

Where does the service air pressure present at the inlet port of the quick release valve vent to when the brakes are releasing?

Answer 15

The inlet for pressure vents to atmosphere through the dual brake valve exhaust port

Question 16

What best describes the purpose of the secondary brake circuit?

Answer 16

The secondary brake circuit is to allow the operator to control the application and release of the steer axle brakes

Question 17

What best describes “cracking pressure”?

Answer 17

The pressure required to move the relay valve piston down closing the exhaust valve and opening the inlet valve

Question 18

What best describes the term “differential pressure” in a relay valve?

Answer 18

Differential pressure is the difference between the control pressure and the delivery pressure

Question 19

What is the material which removes the moisture from the air as it moves through the air dryer?

Answer 19

Dessicant

Question 20

Air reservoirs must store a volume of air equal to 12 times the combined volume of the brake chambers on the unit.

Answer 20

Air reservoirs must store a volume of air equal to 12 times the combined volume of the brake chambers on the unit.

Question 21

What is the purpose of the single check valve in the air reservoirs?

Answer 21

The single check valve ensure the system will have pressure in the event of a reservoir pressure loss.

Question 22

What is the purpose of the safety valve?

Answer 22

The safety valve protects the system from excess pressure in the event of governor failure.

Question 23

Flexible hose is used near brake chambers to allow for movement

Answer 23

Flexible hose is used near brake chambers to allow for movement

Question 24

What is true about a dual circuit brake valve

Answer 24

The primary delivery port is open to the exhaust port in the released position

Question 25

What valve is replaced by the bobtail valve?

Answer 25

The standard relay valve

Question 26

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:

Answer 26

2000 hp

Question 27

One advantage that air brake systems have is that:

Answer 27

The system does not have to be bled when connecting or disconnecting trailers like hydraulic braking systems do

Question 28

If the weight of a vehicle is doubled, the power required to stop the vehicle will:

Answer 28

Be doubled

Question 29

If the speed of a moving vehicle is doubled, the power required to stop the vehicle will:

Answer 29

Be increased four times

Question 30

If both the speed and weight of a moving vehicle are doubled, the power required to stop the vehicle will:

Answer 30

Be increased eight times

Question 31

The term lag time refers to the time required:

Answer 31

For the air system to apply the brakes

Question 32

The component of the basic air system that allows the operator to regulate brake application pressure is the:

Answer 32

Brake valve

Question 33

Brake lining edge code identifies the lining by:

Answer 33

The initials of the manufacturer, The normal coefficient of friction, The hot coefficient of friction

Question 34

Using brake lining with a GAWR that is too low can result in:

Answer 34

Brake fade

Question 35

The caliper of an air disc brake must be able to slide on its mounting pins so the:

Answer 35

Outboard brake pad contacts the brake rotor

Question 36

When an air brake compressor piston is on its compression stroke, the inlet valve:

Answer 36

Is closed and the discharge valve is open

Question 37

When the compressor is in its unloaded cycle:

Answer 37

The inlet valves are held open

Question 38

The governor controls maximum air system pressure by:

Answer 38

Putting the compressor in the unloaded cycle

Question 39

The automatic drain valve drains moisture and contamination from the reservoir when

Answer 39

Any drop in reservoir pressure

Question 40

Air brake antifreeze is used in the air brake system to

Answer 40

Prevent moisture in the system from freezing

Question 41

Single check valves are installed in the inlet line to both the primary and the secondary service reservoirs because they:

Answer 41

Prevent air loss in the event of a failure in the other reservoirs

Question 42

The function of a safety valve is to

Answer 42

Limit air pressure build up in the event of a governor failure

Question 43

CMVSS 121 states the minimum pressure at which the low pressure warning devices must warn the operator is:

Answer 43

60 psi

Question 44

The function of the relay valve in the primary brake circuit is to speed up the:

Answer 44

Application and release of the primary service brakes

Question 45

During normal brake applications, the secondary piston of the dual-circuit brake valve is applied by:

Answer 45

Primary service air pressure

Question 46

Air supply for parking/emergency brake operation flows through a double check valve so that the emergency brakes will:

Answer 46

Not apply if either service reservoir air pressure is lost

Question 47

The function of the park control valve is to provide manual:

Answer 47

And automatic control of all the parking/emergency brakes on the unit

Question 48

A quick release valve is often used in parking/emergency brake Circuits to provide quick:

Answer 48

Application of the spring brakes