Combination Vehicle #3
Why should you lock the tractor glad hands (or dummy couplers) to each other when you are not towing a trailer?
If you did not, you could never build system pressure.
You should never do this.
It will keep dirt and water out of the lines.
The connected brake circuit becomes a back up air tank.
The safety catch for the fifth wheel locking lever must be ____ for a coupling to be complete.
Inside the locking lever
Under the locking lever
Through the locking lever
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 tractor frame and the landing gear.
There is enough clearance between the tops of the tractor tires and the nose of the trailer.
Both answers are correct
None of the answers are correct
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.
None of the answers are correct
Tractor spring brakes to lock on.
Trailer tank pressure to be lost.
When backing a tractor under a trailer you should expect:
Trailer will be lifted slightly when the tractor backs under it.
No movement of the trailer if you've done it correctly.
End of the kingpin is even with the top of the fifth wheel.
Trailer landing gear is fully extended.
You are coupling a tractor to a semi trailer and have backed up but are not under it. What should you hook up before backing under?
The safety chain.
Nothing, back up and lock the fifth wheel.
The electrical service cable.
The emergency and service air lines.
You have coupled with a semi trailer. In what position should you put the front trailer supports before driving away?
None of the answers are correct.
Raised 1/2 way with the crank handle removed.
Fully raised with the crank handle secured in its bracket.
Three turns off the top with the crank handle secured in it?s bracket.
Air lines on a combination vehicle are often colored to keep them from getting mixed up. The emergency line is ____; the service line is ____.
Red, blue
Depends on the type of trailer
Black, yellow
Blue, red
Which of these statements is true?
"Bobtail" tractors can take longer to stop than a combination vehicle loaded to the maximum gross weight.
Light vehicles need more braking power to stop than heavy ones.
Always delay braking a heavy vehicle until you have no other choice.
None of the answers are correct.
You are coupling a tractor and semi trailer and have connected the air lines. Before backing under the trailer, you should:
Apply the brakes twice to alert others.
Make sure that the trailer brakes are off.
Check for leaks.
Supply air to the trailer system, then pull out the air supply knob to lock the trailer brakes.
When uncoupling, if you park the trailer at an angle...
You'll have more room to maneuver in the yard
You won't have to do as much walking around the vehicle
You'll make the process easier
You could do damage to the landing gear
If you start a trailer skid you should...
Release the brakes to get traction back
Use the trailer hand brake
Step on the brakes quickly
Slowly apply pressure to the brakes
When coupling the glad hands, you should NOT do the following...
Clean the couplers before a connection is made
Press the two seals together at a 90 degree angle
Cross air supply lines to test them for leaks
Match the colors to each other, or read the tags before connecting
If you cross connect the two air lines the following will result...
You will not have air going to the trailer brakes
Your tractor brakes will lock up
You could not move the tractor
Nothing, the lines are interchangeable
When rolling up the landing gear to complete the coupling process...
Use high gear to speed up the process
Leave the landing gear half way down to make uncoupling easier later
You could not move the tractor
Use low gear until the tractor is supporting the trailer
A device which connects the service and emergency air lines from the truck to the trailer is called...
Service couplers
Relay switch
Glad hands
Shut off valves
The service air line is controlled by...
The pressure applied to the line by the foot brake or the trailer hand brake
All answers are correct.
The relay valve which sends air pressure from the trailer air tank to the trailer brake chambers
The relay valve which connects the trailer air tanks to the trailer air brakes
To prevent rollovers, remember to...
Keep the load centered
All answers are correct.
Keep the load as low as possible
Go slow around turns
"Off-tracking" occurs when you go around a corner and...
The rear wheels follow the front ones in a straight line
The rear trailer goes off the road
The front of the trailer pulls to the right
The rear wheels follow a different path than the front wheels
Large combination vehicles take longer to stop...
When they are loaded
When they are empty
Than bobtail tractors
It takes the same time whether empty or loaded
Before you back under a trailer, make sure the:
Tractor protection valve is normal.
Landing gear is up.
Air brakes are off.
Trailer brakes are locked.
If the service air line comes apart while you are driving a combination vehicle but the emergency line stays together, what will happen right away?
The trailer's air tank will exhaust through the open line.
Nothing is likely to happen until you try to apply the brakes.
You'll come to a complete stop.
The emergency tractor brakes will come on.
The air leakage rate for a combination vehicle (engine off, brakes on) should not be more than ____ psi per minute.
3
2.5
4
2
In normal driving, some drivers use the hand valve before applying the brake pedal to prevent a jackknife. Which of these statements is true?
It is the best way to brake and keep the truck in a straight line.
It should not be done.
It should only be used if you're aware of the dangers.
It results in less skidding than using the brake pedal alone.
The driver crosses the air lines when hooking up to an old trailer. What will happen?
None of the answers are correct.
The hand valve will apply the tractor brakes instead of the trailer brakes.
If the trailer has no spring brakes, you can drive away, but you will not have trailer brakes.
The brake pedal will work the trailer spring brakes instead of the air brakes.
The hand valve should be used:
To test the trailer brakes.
Only when the trailer is fully loaded.
Only in emergencies.
Only with the foot brake.
The air leakage rate for a combination vehicle (engine off, brakes off) should be no more than ____ psi per minute.
1
3
4
2
The fifth wheel locking lever is not locked after the jaws close around the kingpin. This means that:
You can set the fifth wheel for weight balance.
The coupling is not right and should be fixed before driving the vehicle.
The fifth wheel needs to be replaced.
The parking lock is off and you may drive away.
You are driving a combination vehicle when the trailer breaks away, pulling apart both air lines. You would expect the trailer brakes to come on and:
The tractor protection valve to open.
The tractor protection valve to close.
The tractor to lose all air pressure.
The trailer supply valve to stay open.
Semi trailers made before 1975 that are equipped with air brakes:
Often do not have spring brakes.
Only were equipped with spring brakes.
Are easier to brake because they are heavier.
Usually need a glad hand converter.
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