Section 5: Air Brakes

Front 1

Air brakes use ____________ ___________ to make the brakes work.

Back 1

compressed air

Front 2

Air brakes are really three different braking systems:

Back 2

-service brake
-parking brake
-emergency brake

Front 3

The ____ ________ pumps air into the air storage tanks reservoirs

Back 3

air compressor

Front 4

The ________ controls when the air compressor will pump air into the air storage tanks.

Back 4

governor

Front 5

When air tank pressure rises to the “cut-out” level (around ____ pounds per square inch or “psi”), the governor stops the compressor from pumping air.

Back 5

125

Front 6

When the tank pressure falls to the “cut-in” pressure (around _____ psi), the governor allows the compressor to start pumping again.

Back 6

100

Front 7

Compressed air usually has some _______ and some compressor oil in it which is bad for the air brake system. Be sure that you drain the air tanks completely.

Back 7

water

Front 8

Each air tank is equipped with a drain valve in the
bottom. There are two types:

Back 8

Manual & automatic

Front 9

Some air brake systems have an _________ __________ to put alcohol into the air system. This helps to reduce the risk of ice in air brake valves and other parts during cold weather.

Back 9

alcohol evaporator

Front 10

Check the alcohol container and fill up as necessary, every day during cold weather. __________ air tank drainage is still needed to get rid of water and oil.

Back 10

Daily

Front 11

A ________ _________ valve is installed in the first tank the air compressor pumps air to.

Back 11

safety relief

Front 12

The safety valve protects the tank and the rest of the system from too much __________. The valve is usually set to open at 150 psi.

Back 12

pressure

Front 13

You put on the brakes by pushing down the brake pedal. It is also called the ______ valve or _______ valve.

Back 13

foot valve
treadle valve

Front 14

Foundation brakes are used at each wheel. The most common type is the ______ _______ brake

Back 14

s-cam drum

Front 15

Brake drums are located on each end of the vehicle’s _________.

Back 15

axles

Front 16

Too much ________ can make the brakes stop working.

Back 16

heat

Front 17

Air pressure pushes the rod out, moving the slack adjuster, thus twisting the brake cam shaft. This turns the _________ so called because it is shaped like the letter “S”.

Back 17

s-cam

Front 18

_________ brakes may have a single brake chamber, or two brake chambers, pushing wedges in at both ends of the brake shoes.

Back 18

Wedge

Front 19

In air-operated disc brakes, air pressure acts on a brake chamber and slack adjuster, like s-cam brakes. But instead of the s-cam, a “________ __________” is used.

Back 19

power screw

Front 20

Wedge brakes and disc brakes are _______ common than s-cam brakes.

Back 20

less

Front 21

All air-braked vehicles have a ________ ________ connected to the air tank.

Back 21

pressure gauge

Front 22

A low air pressure warning signal is required on vehicles with air brakes. A warning signal you can see must come on before the air pressure in the tanks falls below ______ psi.

Back 22

60

Front 23

What device drops a mechanical arm into your view when the pressure in the system drops below 60 psi?

Back 23

Wig-Wag

Front 24

__________ valves were used to reduce the chance of the front wheels skidding on slippery surfaces.

Back 24

Limiting

Front 25

________ wheel braking is good under all conditions

Back 25

Front

Front 26

All trucks, truck tractors, and buses must be equipped with emergency brakes and parking brakes. They must be held on by ______________ force (because air pressure can eventually leak away).

Back 26

mechanical

Front 27

In newer vehicles with air brakes, you put on the parking brakes using a ______________, yellow, push-pull control knob.

Back 27

diamond-shaped

Front 28

In some vehicles a control handle on the dash board may be used to apply the spring brakes gradually. This is called a ____________ ___________.

Back 28

modulating valve

Front 29

With duel parking contol valves when main air pressure is lost, the _________ brakes come on.

Back 29

spring

Front 30

Most newer heavy-duty vehicles use ________ air brake systems for safety.

Back 30

dual

Front 31

A dual air brake system has two separate air
brake systems which use a single set of brake controls. These are called:

Back 31

Primary and Secondary

Front 32

Before driving a vehicle with a dual air system, allow time for the air compressor to build up a minimum of _____ psi pressure in both the primary and secondary systems.

Back 32

100

Front 33

The warning light and buzzer should shut off when air pressure in both systems rises to a value set by the manufacturer. This value must be ___________ than 60 psi.

Back 33

greater

Front 34

Park on level ground and chock the wheels to prevent the vehicle from moving. Turn off the _________ brakes so you can move the slack adjusters.

Back 34

parking

Front 35

Brake drums (or discs) must not have cracks longer than ______ _______ the width of the friction area.

Back 35

one half

Front 36

When testing the air leakage rate the loss rate should be less than ______ psi in one minute for single vehicles and less than three psi in one minute for combination vehicles.

Back 36

two

Front 37

Chock the wheels, release the parking brakes when you have enough air pressure to do it, and shut the engine off. Step on and off the brake pedal to reduce the air tank pressure. What are you checking?

Back 37

Spring brakes come on automatically

Front 38

When the spring breaks come on automatically: The “________ _________” knob should pop out when the air
pressure falls to the manufacturer’s specification (usually in a range between 20-40 psi).

Back 38

parking brake

Front 39

When the engine is at operating rpm, the pressure should build from _____ to 100 psi within 45 seconds in dual air systems.

Back 39

85

Front 40

Pumping by the air compressor should start at
about 100 psi and stop at about ______ psi.

Back 40

125

Front 41

With this method, you apply the brakes as hard as you can without locking the wheels.

Back 41

Controlled braking

Front 42

Apply your brakes all the way. Release brakes when wheels lock up. As soon as the wheels start rolling, apply the brakes fully again.

Back 42

Stab Breaking

Front 43

Perception Distance + Reaction Distance + Brake Lag Distance + Effective Braking Distance =

Back 43

Total Stopping Distance

Front 44

At 55 mph for an average driver under good traction and brake conditions, the total stopping distance is over _____ feet.

Back 44

300

Front 45

Brakes can fade or fail from excessive _________ caused by using them too much and not relying on the engine braking effect.

Back 45

heat

Front 46

Brake fade is also affected by _______________.

Back 46

adjustment

Front 47

If your “safe” speed is 40 mph, you would not apply the brakes until your speed reaches 40 mph. You now apply the brakes hard enough to gradually reduce your speed to 35 mph and then release the brakes. What technique is this?

Back 47

Proper braking technique

Front 48

What should you do if your low air pressure warning comes on?

Back 48

Stop & safely park your vehicle as soon as possible.

Front 49

Any time you park, use the parking brakes,
except when the brakes are very _______ or ________.

Back 49

hot or wet

Front 50

If your vehicle does not have automatic air tank drains, drain your air tanks at the end of each ________ _______ to remove moisture and oil.

Back 50

working day