CDL QUIZ Air Brakes Flashcards
- Do converter dollies have spring brakes?
Yes
- What is the emergency air-line for?
1 supplies air to the trailer air tanks; 2 controls the emergency brakes on combination vehicles.
What are the maximum leakage rates?
The loss rate should be less than two psi in one minute for single vehicles and less than three psi in one minute for combination vehicles
- What might happen if the trailer is too high when you try to couple?
if the trailer is too high, it may not couple correctly
- Where are shut-off valves?
at the back of trailers used to tow other trailers
- Why should you pull a dolly out from under a trailer before you disconnect it from the trailer in front?
the dolly tow bar may fly up and possibly cause injury and making it quite difficult to recouple
Why must air tanks be drained?
Compressed air usually has some water and some compressor oil in it, which is bad for the air brake system
- Why should you not use the trailer hand valve while driving?
danger of making the trailer skid.
What are spring brakes?
held on by mechanical force
How can you test the low pressure warning signal?
Shut the engine off when you have enough air pressure Turn the electrical power on and step on and off the brake pedal; warning signal must come on before the pressure drops to less than 60 psi (or tank with the lowest air pressure, in dual air systems)
How often should you drain air tanks?
at the end of each day of driving
- What do you check when making a visual check of coupling?
Make sure there is no space between upper and lower 5th wheel and that the locking jaws are locked on the kingpin
How do you know if your vehicle is equipped with antilock brakes?
Tractors, trucks, and buses will have yellow ABS malfunction lamps on the instrument panel
How can you check that the spring brakes come on automatically?
stepping on and off the brake pedal to reduce tank pressure. The tractor protection valve and parking brake valve should pop out on a tractor-trailer combination vehicle when the air pressure falls to the manufacturer’s specification (20 – 45 psi). This will cause the spring brakes to come on.
- What is a converter dolly?
a coupling device of one or two axles and a fifth wheel
- Describe what the trailer air supply control does.
keeps air in the tractor or truck brake system should the trailer break away or develop a bad leak.
How can you check slack adjusters?
Chock the vehicle and release the park brake
- What type of trailers can get stuck on the railroad-highway crossings?
Low slung units (lowboy, car carrier, moving van, possum-belly livestock trailer); Single-axle tractor pulling a long trailer
- Should the shut-off valves on the rear of the last trailer be open or closed? On the first trailer in a set of doubles? On the middle trailer of a set of triples?
• Rear of front trailers: OPEN; Rear of last trailer: CLOSED; Converter dolly air tank drain valve: CLOSED
- Describe what the service line is for.
trailer brakes
- How do you check to make sure trailer height is correct before coupling?
It must be slightly lower than the center of the fifth wheel so trailer is raised slightly when dolly is pushed under
- What is off-tracking?
When a vehicle goes around a corner, the rear wheels follow a different path than the front wheels.
- What three methods can you use to secure a second trailer before coupling?
Drive tractor close to the trailer and connect the emergency line charge the trailer air tank and disconnect the emergency line. This will set the emergency brakes
- After coupling, how much space should be between the upper and lower fifth wheel?
no space
