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Questions and Answers
What is a converter dolly?
It 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.
Do converter dollies have spring brakes?
True
What three methods can you use to secure a second trailer before coupling?
- Connect the emergency line, charge the trailer air tank, and disconnect the emergency line. 2) Spring brakes. 3) Wheel chocks.
How do you check to make sure trailer height is correct before coupling?
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What do you check when making a visual check of coupling?
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Why should you pull a dolly out from under a trailer before you disconnect it from the trailer in front?
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What should you check for when inspecting the converter dolly?
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Should the shut-off valves on the rear of the last trailer be ______? On the first trailer in a set of doubles? On the middle trailer of a set of triples?
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How can you test that air flows to all trailers?
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How do you know if your converter dolly is equipped with antilock brakes?
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Study Notes
Converter Dolly and Coupling
- A converter dolly is a coupling device with one or two axles and a fifth wheel that connects a semitrailer to a tractor-trailer, forming a double bottom rig.
- Converter dollies are equipped with spring brakes, ensuring safety during operation.
Securing Second Trailer
- Three methods to secure a second trailer before coupling include:
- Connecting the emergency line, charging the trailer air tank, and then disconnecting the emergency line.
- Engaging spring brakes.
- Utilizing wheel chocks.
Trailer Height Check
- Before coupling, the trailer height must be slightly lower than the center of the fifth wheel, allowing it to raise slightly when the dolly is pushed underneath.
Coupling Visual Inspection
- During a visual check of the coupling:
- Ensure there is no space between the upper and lower fifth wheel.
- Confirm that the locking jaws are closed around the kingpin.
Safety Precautions
- It's essential to pull a dolly out from under a trailer before disconnecting it from the trailer in front to prevent the dolly tow bar from flying up, which can cause injury and complicate re-coupling.
Converter Dolly Inspection
- When inspecting the converter dolly:
- Ensure the spare tire, if carried, is secured.
- Check that the pintle hook is latched.
Shut-off Valve Positions
- The shut-off valves on the last trailer in a set of doubles should be closed, while those on the first trailer must be open. In a set of triples, the shut-off valves on the middle trailer should also be open.
Air Flow Testing
- To test that air flows to all trailers, follow these steps:
- Wait for normal air pressure.
- Push in the red "trailer air supply" knob to supply air to the emergency (supply) lines.
- Use the trailer handbrake for service line air supply.
- Open the emergency line shutoff valve at the rear of the last trailer; audible air escaping confirms the system is charged.
Antilock Brakes
- Converter dollies manufactured on or after March 1, 1998, are required to have a lamp on the left side to indicate the presence of antilock brakes.
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Description
Test your knowledge on doubles and triples in commercial driving with this quiz. Learn about converter dollies, their components, and secure coupling methods. Perfect for CDL aspirants looking to deepen their understanding of combination vehicles.
