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Doubles And Triples Free CDL Practice Tests
Page 3

Prepare For The Doubles And Triples Portion Of Your CDL Written Exams

Doubles And Triples Questions

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Good Luck!

The pintle hook should never be unlocked when:
  • The dolly is still under the rear trailer
  • There is nobody around to help you
  • The truck is running
  • The dolly is not under a trailer
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From The CDL Manual

Never unlock the pintle hook with the dolly still under the rear trailer. The dolly tow bar may fly up, possibly causing injury and making it very difficult to re-couple.

Next
The last step to uncouple a converter dolly is:
  • Release pintle hook
  • Pull clear of the dolly, slowly
  • Disconnect the safety chains
  • Lower landing gear
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From The CDL Manual

Uncouple converter dolly:

  • Lower dolly landing gear.
  • Disconnect safety chains.
  • Apply converter gear spring brakes or chock wheels.
  • Release pintle hook on first semitrailer.
  • Slowly pull clear of dolly.
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Next
When inspecting doubles and triples shut-off valves, which of the following is true?
  • All of these are correct
  • Converter dolly air tank drain valve is closed
  • Rear of front trailers are open
  • Rear of last trailer is closed
Click here to look up the answer

From The CDL Manual

Shut-off valves (at rear of trailers, in service and emergency lines)

  • Rear of front trailers: OPEN
  • Rear of last trailer: CLOSED
  • Converter dolly air tank drain valve: CLOSED
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Next
When inspecting the shut-off valves on doubles and triples, all of the following is true except:
  • Rear of last trailer: CLOSED
  • Rear of front trailers: CLOSED
  • Converter dolly air tank drain valve: CLOSED
  • Rear of front trailers: OPEN
Click here to look up the answer

From The CDL Manual

Shut-off valves (at rear of trailers, in service and emergency lines)

  • Rear of front trailers: OPEN
  • Rear of last trailer: CLOSED
  • Converter dolly air tank drain valve: CLOSED
Prev
Next
When checking that air is flowing to all trailers,what is used to provide air to the supply lines?
  • The blue trailer air supply knob
  • The red trailer air supply knob
  • The tractor foot brake
  • The trailer handbrake
Click here to look up the answer

From The CDL Manual

Check air flow to all trailers:

Use the tractor parking brake and or chock the wheels to hold the vehicle. Wait for air pressure to reach normal, then push in the red “trailer air supply” knob. This will supply air to the emergency (supply) lines. Use the trailer handbrake to provide air to the service line.

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Next
Which is true when checking air flow to all trailers?
  • The emergency shut-off valve should be closed, and you should not hear air escaping
  • The emergency shut-off valve should be open, and you should not hear air escaping
  • The emergency shut-off valve should be open, and you should hear air escaping
  • The emergency shut-off valve should be closed, and you should hear air escaping
Click here to look up the answer

From The CDL Manual

Go to the rear of the rig. Open the emergency line shut-off valve at the rear of the last trailer. You should hear air escaping, showing the entire system is charged.

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Next
To test the tractor protection valve, the engine needs to be:
  • Off
  • Revving at high RPM's
  • Hot
  • On
Click here to look up the answer

From The CDL Manual

Test tractor protection valve:

Charge the trailer air brake system, (i.e., build up normal air pressure and push the “air supply” knob in). Shut the engine off.

Step on and off the brake pedal several times to reduce the air pressure in the tanks.

The trailer air supply control (also called the tractor protection valve control) should pop out (or go from “normal” to “emergency” position) when the air pressure falls into the pressure range specified by the manufacturer (usually within the range of 20 to 45 psi).

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Next
The tractor protection valve should pop out when air pressure falls to:
  • 60 psi
  • 0 psi
  • Between 20 and 45 psi
  • Between 80 and 100 psi
Click here to look up the answer

From The CDL Manual

Test tractor protection valve:

Charge the trailer air brake system, (i.e., build up normal air pressure and push the “air supply” knob in). Shut the engine off.

Step on and off the brake pedal several times to reduce the air pressure in the tanks.

The trailer air supply control (also called the tractor protection valve control) should pop out (or go from “normal” to “emergency” position) when the air pressure falls into the pressure range specified by the manufacturer (usually within the range of 20 to 45 psi).

Prev
Next
When testing the trailer emergency brakes, charge the system, pull out the trailer air supply control, and:
  • Put the tractor in gear at high RPM's
  • Drag the trailer a few feet
  • Pull gently on the trailer
  • Reverse and pull forward rapidly
Click here to look up the answer

From The CDL Manual

Charge the trailer air brake system and check that the trailer rolls freely. Then stop and pull out the trailer air supply control (also called tractor protection valve control or trailer emergency valve) or place it in the “emergency” position. Pull gently on the trailer with the tractor to check that the trailer emergency brakes are on.

Prev
Next
You will test that the trailer service brakes are working by:
  • Applying the brakes with the foot pedal
  • Applying the parking brake
  • Pumping the foot pedal rapidly
  • Applying the brakes with the hand control
Click here to look up the answer

From The CDL Manual

Test trailer service brakes:

Check for normal air pressure, release the parking brakes, move the vehicle forward slowly, and apply trailer brakes with the hand control (trolley valve), if so equipped. You should feel the brakes come on.

This tells you the trailer brakes are connected and working. (The trailer brakes should be tested with the hand valve, but controlled in normal operation with the foot pedal, which applies air to the service brakes at all wheels.)

Prev
Next
A danger of a malfunctioning tractor protection valve is:
  • Loss of control
  • All of these things
  • A leak could drain all the air from the tractor
  • Emergency brakes could come on unexpectedly
Click here to look up the answer

From The CDL Manual

If the tractor protection valve does not work properly, an air hose or trailer brake leak could drain all the air from the tractor. This would cause the emergency brakes to come on, with possible loss of control.

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