Heavy Vehicle Braking Flashcards
What is motion energy converted into in order for a vehicle to stop?
Heat, through friction
What is the final factor in determining if a vehicle will move?
Traction
What creates more braking force: Air Brakes or Hydraulic Brakes?
Air Brakes
What factors determine the total stopping time?
Driver’s perception time + Reaction Time + Brake Lag Time + Braking time
2 X Vehicle Speed equals how much stopping power?
4X
2X Vehicle weight = how much stopping power
2X
2X Vehicle weight + 2X Vehicle Speed = how much stopping power
8X
What temperature do brake components work best at?
120°C
What is the maximum temp of brake components?
250°C
What is Brake Fade?
Brake fade occurs when your brakes stop working properly because they’re overheated. The vehicle will take longer to stop, or may not stop at all.
What are retarders?
They provide an auxiliary slowing effect, and assist the main brake system to stop the vehicle.
What are the 4 main types of retarders?
Engine retarders, Exhaust retarders, Hydraulic driveline retarders, Electric Driveline retarders
When do retarders work best?
When the vehicle is at higher RPM and lower speeds. Make sure you are in the right gear before approaching a downgrade
What can happen when using engine retarders/brakes on slippery surfaces?
The wheels could lock up, stalling the engine and resulting in a jackknife
What is RPM
Revolutions per minute - The number of times the crankshaft makes a complete turn per minute.
How do you prevent a jerking stop?
By reducing the pressure on the brakes before making a complete stop.
What are three steps to ensure a smooth controlled stop?
- Travel at speeds that allow you to see a safe distance ahead
- Maintain safe following time/distance
- Use good braking skills
When should you apply chains on tires?
Before you reach a hill, in a designated chain-up area
What type of pressure should you use to stop on icy roads?
Extremely light pressure.
How can you prevent overheating brakes?
Using a lower gear, travelling a slower speeds
How can you go down a hill without using service brakes?
- Safe speed
- Right low gear
- Using the vehicles retarding device
What should you do when driving through water?
Cover the brakes with light pressure to prevent water getting on them.
After, test the brakes with slight pressure. Keep the pressure for a short distance to dry out the brakes.
What can happen when brakes are applied to forcefully.
Can cause wheels to seize, resulting in a jackknife
What is a jackknife?
When the tractor and trailer form an angle of 90 degrees or less, relative to one another.
How should you stop with ABS?
- Apply direct firm pressure
- Don’t pump brakes. This turns the system on and off.
- Don’t be alarmed by brake noise or shutter.
- Me cautious when making turns.
- If all of the trailers don’t have ABS, then act as if there is no ABS.
What does ABS do?
It helps prevent wheel lock up, and skids from overbraking on slippery surfaces
What is Automatic Traction Control (ATC)?
An addition to ABS. It detects the loss of drive wheel traction on slippery surfaces.
How does ATC work?
It uses the same sensors as ABS, and can tell if a wheel is spinning with no traction. It can compensate by adding power to the opposite wheel, or reduce engine power to allow the wheels to regain traction.
What is brake lag time?
The time between when you apply brakes, and the brake system begins to work.
