Chapter 2 Heavy Vehicle Braking

Question 1

What is Heat and its relation to an engine

Answer 1

Heat is a form of energy produced in the engine and this energy is converted into the energy of motion through the moving parts of the engine and drive train turning the wheels.

Question 2

What role does traction play in moving a vehicle

Answer 2

if there is no traction Between the tires and the road surface the vehicle will not move anywhere

Question 3

How does the vehicle stop using scientific explination

Answer 3

in stopping a vehicle energy of motion is converted to the energy of heat through friction between the lining/pad and drum/rotor surfaces of the vehicles breaks

Question 4

What is the final factor in stopping the vehicle

Answer 4

The final factor is in the contact between the vehicle and the road through the tire
bald or defective tires may degrade braking performance.

Question 5

What is reaction time

Answer 5

is the time it takes between recognizing a hazard ahead and applying the brakes
An average drivers reaction time is 3/4 a second

Question 6

What happens If one of the brakes aren’t adjusted properly on a tire

Answer 6

It would cause the other brakes to work harder. Excessive use could result in buildup of more heat than the brake can absorb and dissipate. too much heat can result in brake damage and possible failure.

Question 7

What is see-think-do

Answer 7

see-a hazard
think-decide to stop
do-place your foot on the brake pedal until you stop

Question 8

What equals to total stopping time

Answer 8

Drivers perception time + reaction time + brake lag time + braking time = total stopping time

Question 9

how long does it take to perceive a hazard

Answer 9

3/4 of a second

Question 10

how long does it take to react to a hazard after percieving it

Answer 10

3/4 of a second

Question 11

What is brake lag time

Answer 11

Brake lag time is the time between when you press the brakes to when they actually apply is 4/10 of a second

Question 12

How many seconds behind should you follow a vehicle if you’re in a heavy vehicle

Answer 12

never be less then 5 seconds (stay even further back if in bad conditions)

Question 13

What happens if your brakes aren’t correctly adjusted

or your vehicles on a downgrade while braking

Answer 13

total stopping time will increase

Question 14

What is the most common air brake defect found during commercial vehicle inspections

Answer 14

brakes out of adjustment

Question 15

What does the total stopping distance or time depend on

Answer 15

The ability of the brake linings or pads to produce friction the brake drums to dissipate heat and the tires to grip the road

Question 16

what 2 factors are mostly in play involved in police reported casualty crashes

Answer 16

Driving without due care and attention and unsafe speeds are the 2 factors in casualty related crashes

Question 17

if a vehicle is going double the speed and it needs to brake how much more stopping power is required to stop it

Answer 17

4 times the stopping power

Question 18

If a vehicle is double the weight and it needs to brake how much more stopping power is required to stop it

Answer 18

2 times the stopping power

Question 19

If a vehicle is going double the speed and double the weight how much stopping power is required to stop it

Answer 19

8 times the stopping power

Question 20

What is Stopping power

Answer 20

stopping power is the distance required to stop

Question 21

Going down hill does what to braking

Answer 21

increases brake time

Question 22

going up hill does what to braking

Answer 22

decreases braking time

Question 23

What is Brake fade

Answer 23

Brake fade occurs when your brakes stop working properly because they’re overheating your vehicle takes longer to stop or may not stop at all if you haven’t properly controlled the speed

Question 24

In normal stopping what is the heat the brake component heats up to?

Answer 24

120 degrees Celsius or 250 Fahrenheit

Question 25

What is the maximum heat the brakes are meant to with stand under hard braking circumstances

Answer 25

250 degrees Celsius

Question 26

What happens when the brake drums heat up to much

Answer 26

to much heat causes the brake to expand away from the brake lining causing in the end brake fade, brake damage and or brake failure. (may catch on fire)

Question 27

When braking what happens

Answer 27

Heat builds up with excessive hard braking until it exceeds the capability of the brake components to absorb and dissipate the heat

Question 28

What is a Retarder

Answer 28

Reatrders provide an auxiliary slowing effect and assist the main brake system to slow the vehicle. good for controlling speed on long downgrades of hill. Many retarders can absorb as much or more horse power as the engine can develop

Question 29

What are the 4 main type of rearders

Answer 29

• Engine retarder
• Exhaust Retarder
• Hydraulic drive line retarders
• electric driveline retarder

Question 30

When is an engine retarder more efficient

Answer 30

at a higher rpm and a lower vehicle speed, Selecting the right gear before going down hill is important

Question 31

What should you be cautious of when using a retarder/engine brake

Answer 31

On slippery surfaces some can actually cause the drive wheels to lock up, stalling the engine and can result to loss of control of even the tractor trailer to jack knife

Question 32

When are retarders restricted

Answer 32

Watch for signs restricting the use of retarders and engine brakes

Question 33

What does R.P.M. stand for

Answer 33

Revolutions per minuter refers to the number of complete turns the crankshaft make in one minute

Question 34

How should you normally brake

Answer 34

Gradually squeezing the brake and before you stop reduce the pressure so your vehicle wont jerk

Question 35

How to ensure a smooth controlled stop every time

Answer 35

• travel at a speed allows you to see a safe distance ahead
• maintain a safe following time or distance
• Use good braking skills

Question 36

How to stop safely

Answer 36

Brakes properly adjusted your load is balanced and your tires are in good condition. be sure your tires are inflated

Question 37

How do you stop on icy roads

Answer 37

to stop on icy roads use extremly light pressure on the brake to control vehicle speed. this will help prevent the wheel from locking up. a slow spinning wheels had mor stopping power then a locked up wheel

Question 38

When should you put chains on

Answer 38

When you’re going to drive in bad conditions or potentially going to best be prepared. Its harder to mount chains on a hill.

Question 39

When do the brakes get the hottest

Answer 39

going highway speeds while on a long downgrades. or from repeated use of the brakes without enough cooling time between application.

Question 40

whats the causes the majority of all brake failures and downhill runaway crashes

Answer 40

they’re caused by over driving the ability of brakes to deal with heat. in other words poor speed control

Question 41

in heavy vehicles when going on a downgrade

Answer 41

go slow you should be in a low gear never switch into a higher gear unless it can be controlled by a retarder

Question 42

What does it mean by saving your brakes

Answer 42

on a hill use a retarder and save your breaks for emergency stops

Question 43

If you fail to go slow enough on a downgrade what should you do

Answer 43

apply the brakes to go down 10 to 15 km/h
downshift to a lower main gear(don’t use the splitter valve when going down hill)
Repeat this process if it happens again
be careful when using this process in icy conditions

Question 44

When should you obey brake check signs

Answer 44

Always

Question 45

In town

Answer 45

In town you should select and appropriate low gear that holds speed and so you can safely stop in an emergency

Question 46

Why should you avoid water on road ways

Answer 46

cause it can reduce braking efficiency.

Question 47

why should you apply a slight drag on the brakes

Answer 47

so it reduces the amount of water entering the brake drums and shoes.

Question 48

What are runaway lanes for

Answer 48

these are lanes located on some downgrading hills. These lanes are there to help slow and stop vehicles if their brakes fail as they are going down hill. Runaway lanes should be used to control speed or stop

Question 49

why should you be cautious when braking

Answer 49

wheels can lock up causing them to slide when theres no ABS

Question 50

What is an ABS

Answer 50

anti-lock braking system. It prevents wheel lock up or skids caused by overbraking on slippery surfaces

Question 51

Whats bad when your wheels lock up

Answer 51

You cant steer

Question 52

`What is a Jack knife and what causes it

Answer 52

Jackknife is when a tractor and the trailer form and angle of 90 degrees or less. relative to one another
Happens because of poor braking techniques and improper use of retarders

Question 53

How to emergency stop with abs

Answer 53

• Apply firm hard continuous pressure
• don’t pump the brakes
• Don’t be alarmed by brake noise, pedal movement or shudder. this is normal keep applying firm pressure
• Be cautious about steering around obstacles
• make sure you know if your trailer has abs or not if it doesn’t brake as if you didn’t have abs

Question 54

What is an ATC

Answer 54

Automatic Traction Control is an optional addition to the abs system. It uses a pulsating signal from the speed sensors to select loss of drive wheel traction on slippery roads.
If a wheel doesn’t gain traction the sensor will stop the wheel from spinning to gain traction

Question 55

How is heat dissipated in the brake

Answer 55

its absorbed or dissipated in the brake components