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CDL Practice Test: Doubles And Triples

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CDL Practice Test: Doubles And Triples

Doubles And Triples Questions

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Good Luck!

When pulling more than one trailer:
  • The position of the heaviest trailer is not important as long as the brakes are working properly
  • The heaviest trailer should be the very last trailer
  • The heaviest trailer should be in first position behind the tractor
  • If there are three trailers, the heaviest should be in the middle
This is a question from page 56 - click here to look up the answer

Quote From Page 80 Of The Illinois CDL Manual:

For the safest handling on the road, the more heavily loaded semi-trailer should be in first position behind the tractor. The lighter trailer should be in the rear.

Next
How do you check to make sure the trailer height is correct before coupling?
  • The trailer landing gear should be lowered completely so that you can push the dolly under the trailer and be ready to drive once attached
  • The trailer must be slightly lower than the center of the fifth wheel, so the trailer is raised slightly when dolly is pushed under.
  • The trailer should be slightly higher than the center of the fifth wheel, so the trailer doesn't have to raise up when the dolly is pushed under
  • The trailer should be a minimum of 1ft higher than the fifth wheel, so the trailer king pin will not strike the fifth wheel plate and cause damage
This is a question from page 56 - click here to look up the answer

Quote From Page 81 Of The Illinois CDL Manual:

Connect converter dolly to rear trailer:

  • Make sure trailer brakes are locked and/or wheels chocked.
  • Make sure trailer height is correct. (It must be slightly lower than the center of the fifth wheel, so trailer is raised slightly when dolly is pushed under.)
  • Back converter dolly under rear trailer.
  • Raise landing gear slightly off ground to prevent damage if trailer moves.
  • Test coupling by pulling against pin of number two semi-trailer.
  • Make visual check of coupling. (No space between upper and lower fifth wheel. Locking jaws closed on kingpin.)
  • Connect safety chains, air hoses and light cords.
  • Close converter dolly air tank petcock and shut-off valves at rear of second trailer (service and emergency shut-offs).
  • Open shut-off valves at rear of first trailer (and on dolly if so equipped).
  • Raise landing gear completely.
  • Charge trailers (push "air supply" knob in) and check for air at rear of second trailer by opening the emergency line shut-off. If air pressure is not there, something is wrong and the brakes will not work.
Prev
Next
All of the following are correct steps to positioning the converter dolly in front of the second (rear) trailer except:
  • Wheel dolly into position in front of second trailer in line with the kingpin
  • Pull dolly into position as close as possible to nose of the second semitrailer
  • Be sure the pintle hook is unlocked
  • Move the dolly to rear of first trailer and couple it to the trailer
This is a question from page 56 - click here to look up the answer

Quote From Page 80 Of The Illinois CDL Manual:

Position converter dolly in front of second (rear) trailer:

  • Release dolly brakes by opening the air tank petcock. (Or, if the dolly has spring brakes, use the dolly parking brake control.)
  • If the distance is not too great, wheel dolly into position by hand so it is in line with the kingpin.
  • Or, use the tractor and first semitrailer to pick up the converter dolly:
  • Position combination as close as possible to converter dolly.
  • Move dolly to rear of first semi-trailer and couple it to the trailer.
  • Lock pintle hook.
  • Secure dolly support in raised position.
  • Pull dolly into position as close as possible to nose of the second semitrailer.
  • Lower dolly support.
  • Unhook dolly from first trailer.
  • Wheel dolly into position in front of second trailer in line with the kingpin
Prev
Next
How are dolly brakes released when not equipped with spring brakes?
  • Opening the air tank petcock
  • Brakes will be released when the electrical cable is attached
  • Hooking airlines to the dolly will automatically release the brakes
  • If a dolly doesn't have spring brakes, it doesn't have brakes at all
This is a question from page 56 - click here to look up the answer

Quote From Page 80 Of The Illinois CDL Manual:

Release dolly brakes by opening the air tank petcock. (Or, if the dolly has spring brakes, use the dolly parking brake control.)

Prev
Next
What is a proper way to check the Tractor Protection Valve when pulling double or triple trailers?
  • Chock the wheels, release all brakes, then go to the last trailer and open the shut off valve to release as much air from the system as possible to see if the trailer air supply control pops out
  • Step on and off the brake pedal several times to reduce the air pressure in the tanks until the trailer air supply control pops out
  • Engage and disengage the parking brake repeatedly until the trailer air supply control pops out
  • On double and triple trailers, the tractor protection valve will not work
This is a question from page 59 - click here to look up the answer

Quote From Page 83 Of The Illinois 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
Which of these steps to connecting the converter dolly to the rear trailer is incorrect?
  • Make sure trailer brakes are locked and/or wheels chocked
  • Connect safety chains, air hoses and light cords
  • Back converter dolly under rear trailer
  • Close shut-off valves at rear of first trailer (and on dolly if so equipped)
This is a question from page 56 - click here to look up the answer

Quote From Page 81 Of The Illinois CDL Manual:

Connect converter dolly to rear trailer:

  • Make sure trailer brakes are locked and/or wheels chocked.
  • Make sure trailer height is correct. (It must be slightly lower than the center of the fifth wheel, so trailer is raised slightly when dolly is pushed under.)
  • Back converter dolly under rear trailer.
  • Raise landing gear slightly off ground to prevent damage if trailer moves.
  • Test coupling by pulling against pin of number two semi-trailer.
  • Make visual check of coupling. (No space between upper and lower fifth wheel. Locking jaws closed on kingpin.)
  • Connect safety chains, air hoses and light cords.
  • Close converter dolly air tank petcock and shut-off valves at rear of second trailer (service and emergency shut-offs).
  • Open shut-off valves at rear of first trailer (and on dolly if so equipped).
  • Raise landing gear completely.
  • Charge trailers (push "air supply" knob in) and check for air at rear of second trailer by opening the emergency line shut-off. If air pressure is not there, something is wrong and the brakes will not work.
Prev
Next
Do converter dollies have spring brakes?
  • While some states don't require dollies to have spring brakes, it is required for dollies to have spring brakes on the interstate system
  • All converter dollies are required to have spring brakes if built after 1975
  • Converter dollies don't ever have spring brakes
  • Some converter dollies have spring brakes, but dollies are not required to have them
This is a question from page 56 - click here to look up the answer

Quote From Page 80 Of The Illinois CDL Manual:

A converter gear or dolly is a coupling device of one or two axles and a fifth wheel by which a semitrailer can be coupled to the rear of a tractor-trailer combination forming a double bottom rig.

  • Release dolly brakes by opening the air tank petcock. (Or, if the dolly has spring brakes, use the dolly parking brake control.
Prev
Next
When pulling 3 trailers, the lightest trailer should:
  • The placement of the lightest trailer doesn't matter
  • Be the first trailer
  • Be the last trailer
  • Be the middle trailer
This is a question from page 56 - click here to look up the answer

Quote From Page 80 Of The Illinois CDL Manual:

For the safest handling on the road, the more heavily loaded semi-trailer should be in first position behind the tractor. The lighter trailer should be in the rear.

Prev
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