Combination Vehicles Flashcards
What is one important thing to do to prevent a rollover?
Keep cargo as close to ground as possible
When you turn suddenly while pulling doubles, which trailer is most likely to turn over?
Keep cargo as close to ground as possible
When should you use the trailer handbrake to straighten out a jackknifing trailer?
Never
What is “offtracking”?
- When the rear wheels follow a different path than the front wheels
Why should you not use the trailer hand valve while driving?
- Can make the trailer skid
What does the trailer air supply control do?
Supplies air to the trailer
What is the service line for?
- Carries air controlled by the footbrake or trailer handbrake
1)What is the emergency air line for?
- Supplies air to the trailer air tanks
Where are shut off valves?
At the back of trailers
Why should you lock the glad hands together or to a dummy coupler, when not pulling a trailer?
- Keeps water and dirt out of the lines
How much space should there be between the upper and lower 5th wheel plates?
no space at all
If the trailer breaks away and pulls apart the air lines, the trailer brakes would apply, and:
- The tractor brakes to keep working
When hooking a trailer to a tractor, the trailer is at the right height when:
The coupling surface of the trailer is just below the middle of the tractor 5th wheel
After hooking the trailer to the tractor, check the 5th wheel connection by
Pulling the tractor ahead gently with the trailer brakes locked
What will happen right away if the service line disconnects while you are driving?
Nothing until you try the brakes
When backing up under a trailer, you should line up:
Directly in front of the trailer
When hooking a tractor to a semi trailer, after connecting both air lines and before backing under the trailer, you should
Supply air to the trailer system, then pull the air supply knob to lock the brakes
How do you supply air to the tank on the trailer?
Push in the trailer air supply valve
What color is the emergency air line on a combination vehicle?
Red
When should the valve hand be used to park a combination vehicle?
Never
Air brake equipped trailers that were made before 1975:
Usually don’t have spring brakes
After coupling a semitrailer, how should you crank up(启动) the front trailer supports?
Fully raised with crank handle secured
What can happen when a driver crosses the air lines on an older trailer?
If the trailer does not have spring brakes, you may drive but wouldn’t have trailer brakes
When the 5th wheel locking lever is not locked after the jaws close around the kingpin, what may happen?
The coupling should need to be corrected before driving the coupled unit
With the brakes released and the engine off, a combination vehicle air brake system should not leak more than psi in one minute.
3
What is one thing a driver can do to prevent a rollover?
Slow down before entering a turn
After pushing in the trailer supply valve, do not move the tractor until the entire air system is:
Is above 60 psi and the warning buzzer has stopped
After hooking a tractor to a semitrailer, what should you do before backing under it?
Hook up the service line and emergency line
Which part of the kingpin should the locking jaws close around?
The shank
You should test the semi trailer connection for security by:
Pulling gently forward in low gear against the locked trailer brakes, then looking at it carefully
Why should you be sure that the fifth wheel plate is greased as required?
To prevent steering problems
After you supply air to the trailer, make sure the air lines are not crossed and the trailer brakes are working, by:
Applying and releasing the trailer brakes and listening for sounds
What can be done to prevent a rollover?
Slow down around turns
What is one thing you should do before backing under a trailer?
Make sure the trailer brakes are locked
The safety catch for the fifth wheel locking lever must be for a coupling to be complete.
Over the locking lever
The front trailer supports are up and the trailer is resting on the tractor. Make sure:
There is enough clearance between the tops of the tractor tires and the nose of the trailer and there is enough clearance between the kingpin and the 5th wheel
You have a major leak in the service line and you put on the brakes. Service air pressure will escape and cause the:
Trailer emergency brakes to come on
When backing under a trailer, you should expect:
Trailer to be lifted slightly when the tractor backs under
You have coupled with a semi trailer. In what position should you put the front trailer supports before driving away?
Fully raised with the crank handle secured in its bracket
Which of these statements is true?
Bobtail tractors can take longer to stop than combination vehicles loaded to the maximum gross weight.
What should the hand valve be used for?
To test the trailer brakes
Fully loaded rig(n. 重型铰接式开车)s are 10 times more likely to roll over in a crash than empty rigs.
T
Cargo should be kept as high off the ground as possible.
F
The crack-the-whip(n. 鞭子) effect is caused by rearward(a. 在后面的) amplification(n. 放大).
T
Heavily loaded trailers are more likely to jackknife (v.（铰接车失控时）弯折成V形) than lightly loaded trailers.
F
1)It takes a bobtail longer to stop than a fully loaded tractor-trailer.
T
If you go into a trailer skid, you should use the trailer hand brake to straighten out.
F
Before starting a right turn, you should swing wide to the left.
F
The trailer hand valve should never be used for parking.
T
The rear wheels of the trailer will offtrack the most.
T
The tractor protection valve keeps air in the tractor if the trailer breaks away.
T
Dummy, or dead end couplers prevent water and dirt from getting into the coupler and air lines.
The 5th wheel plate could cause steering problems if not kept properly lubricated.
T
Always back your tractor under your trailer at an angle.
F
The trailer does not need to be level when the tractor is backed under it.
T
The tractor emergency air line should be connected to the trailer emergency glad hand.
T
Crossed air lines are only dangerous if you do not have a tractor emergency brake.
F
When properly coupled, the 5th wheel jaws should be closed around the shank of the kingpin.
T
There are two things a driver can do to prevent a rollover. They are, keep the weight in your vehicle as close to the floor as possible and:
Go slow around corners.
A device which corrects for brake lag on vehicles with air brakes is ?
Relay valve
