ROBERT COMBINATION

ROBERT COMBINATION

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Question Answer
You should not back a tractor under a trailer until the whole air system is At normal pressure
Before you back under a trailer, make sure the Trailer brakes are locked.
You are coupling a semi-trailer to your tractor but you have not yet backed under. The trailer is at the right height when It will be raised slightly when the tractor is backed under it.
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 emergency and service air lines
When you get ready to back under the semi-trailer you should line up Directly in front of the trailer
. 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? Nothing will happen until you try to apply the brakes
Which part of the king pin should the locking jaws close around? The shank
The fifth wheel locking lever is not locked after the jaws close around the king pin. This means that The coupling is not right and should be fixed before driving the coupled unit
How should you test the tractor-semitrailer connection for security? Pull gently forward in low gear against the locked trailer brakes then look at it carefully
Test air leak rate for a combination vehicle (engine off, brake on) ___psi per minute 4
When should you use the hand valve to park a combination vehicle? Never
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
You can supply air to the trailer tanks by: Pushing in the trailer air supply valve
In normal driving, some drivers use the hand valve before applying the brake pedal to prevent a jackknife. Which of these statements are true? It should not be done
The air leakage rate for a combination vehicle (engine off, brakes off) should be less than ____psi per minute 3
Why should you be sure that the fifth wheel plate is greased as required? To prevent steering problems
A driver crosses the air lines when hooking up to an old trailer. What will happen? If the trailer has no spring brakes, you can drive away, but you will not have trailer brakes
After you supply air to the trailer, make sure the air lines are not crossed and the trailer brakes are working. This is done by: Applying and releasing the trailer brakes and listening for brake sounds
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
There are 2 things a driver can do to prevent a roll-over. They are (1) keep the cargo as close to The ground as possible (2) Go slowly around turns
Semi- trailers made before 1975 that are equipped with air brakes: often will not have spring brakes
“Bobtail” tractors can take longer to stop than a combination vehicle loaded to the maximum gross weight, TRUE or FALSE TRUE
Why should you lock the tractor glad hands (or dummy couplers) to each other when you are not towing a trailer? It will keep dirt and water out of the lines.
The hand valve should be used: To test the trailer brake
The safety catch for the fifth wheel locking lever must be ______for a coupling to be complete Over the locking lever
You are coupling a trailer and semi-trailer and have connected the air lines. Before backing under the trailer you should: . Supply air to the trailer system, then pull out the air supply knob to lock the trailer brakes.
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 tractor frame and the landing gear.
Your emergency air line breaks or gets pulled apart why you are driving. The loss of pressure will cause the: Emergency trailer brakes to come on
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
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 close
You are about to back your tractor under a semi-trailer. The trailer is at the right height when the: Trailer will be lifted slightly when the tractor backs under it.
How much space should be between the upper and lower fifth wheel after coupling? None

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