Combination Vehicles Flashcards
What two things are important to prevent rollover?
Keeping a load evenly distributed, low to the ground, and centered in a trailer is the best way to mitigate rollover risk. Additionally, it’s important to drive slowly around turns.
When you turn suddenly while pulling doubles, which trailer is most likely to turn over?
When driving a tractor with two trailers, it is the rearmost trailer that is at the greatest risk of rolling over.
Why should you not use the trailer hand brake to straighten out a jackknifing trailer?
When the trailer wheels lock up it is due to applying the brakes quickly with a lightened trailer. Using the trailer hand brake to straighten the trailer will only worsen the risk of jackknife. It is best to let up the brakes ( if possible) if it seems the trailer is sliding out of the lane.
What is off-tracking?
When turning a corner the rear-wheels of the trailer follow a wider path than the forward-wheels of the trailer. It’s important to turn the tractor wide (as you’re turning, not before) to compensate for the off-tracking of the trailer’s rear-wheels.
When you back a trailer, you should position your vehicle so you can back in a curved path to the driver’s side. True or False?
False. You should position the tractor-trailer in a straight line. However, if you must back along a curved path it is better to back to the driver’s side so it is easier to see the trailer.
What type of trailers can get stuck on railroad-highway crossings?
Trailers that are positioned lower to the ground have an increased risk of getting stuck on railroad crossings. A Single-axle tractor pulling a tandem-axle trailer with landing gear set is also at an increased risk of getting stuck.
Why should you not use the trailer hand valve while driving?
The trailer hand valve activates the brakes of the trailer but unlike the foot pedal, does not activate the brakes of the entire vehicle. Using the trailer hand valve while driving increases the risk of skidding the trailer. Only use the trailer hand valve to test the trailer’s brakes while parked.
Describe what the trailer air supply control does.
The trailer air supply control activates the trailer protection valve which is designed to prevent excessive air pressure loss in the vehicle’s brake system in the event that the trailer becomes disconnected while driving and/or if the air supply develops a leak.The control allows you to manually open and shut the valve. The valve will close automatically if air pressure drops down to 25-40 psi.
Describe what the service line is for.
The service air line supplies air from the tractor’s air brake system to the trailer’s air brakes.
What is the emergency air-line for?
The emergency air-line supplies air from the tractor’s air brake system to the trailer’s air brakes. The emergency line also activates the emergency brakes of the trailer in the event of an air pressure drop in the emergency line caused by a breakage or leak.
Why should you use chocks when parking a trailer without spring brakes?
Parking brakes are not reliable if supported by air pressure alone. It is important to chock the wheels of a trailer that does not have spring brakes to prevent the risk of rolling.
Where are shut-off valves?
Shut-off valves are located at the rear of trailers that are designed to pull other trailers. These shut-off valves allow the driver to close the air-supply reserved for an additional trailer when an additional trailer isn’t in use.
What might happen if the trailer is too high when you try to couple?
If the trailer is too high when attempting to couple there is an increased risk of an incomplete connection.
After coupling, how much space should be between the upper and lower fifth wheel?
There should be no space in between the upper and lower fifth wheel after coupling.
You should look into the back of the fifth wheel to see if it is locked onto the kingpin. True or False?
True. The lock jaw must be clamped around the shank of the kingpin.
