DMV PA - CDL Doubles and Triples Endorsement Text Book Questions (And Answers)

• 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.

(Page 7-2)

Yes, as explained below:

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.)

(Page 7-2)

• COUPLING TWIN TRAILERS
• SECURE SECOND (REAR) TRAILER

• • If the second trailer doesn't have spring brakes, drive the tractor close to the trailer, connect the
• emergency line, charge the trailer air tank, and disconnect the emergency line. This will set the
• trailer emergency brakes (if the slack adjusters are correctly adjusted). Chock the wheels if you
• have any doubt about the brakes.

• COUPLE TRACTOR AND FIRST SEMI-TRAILER AS DESCRIBED EARLIER
• ***Caution: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.***
• 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.

• 1.) 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 semi-trailer 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 semi-trailer.

- Lower dolly support.

- Unhook dolly from first trailer.

- Wheel dolly into position in front of second trailer in line with the kingpin.

2.) CONNECT CONVERTER DOLLY TO FRONT TRAILER

• Back first semi-trailer into position in front of dolly tongue.

• Hook dolly to front trailer.

- Lock pintle hook.

- Secure converter gear support in raised position.

3.) 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 isn't there, something is wrong and the brakes won't
• work.

(Page 7-2/7-3)

• COUPLING SYSTEM AREAS
• • Check fifth wheel (lower):
• - Securely mounted to frame.

- No missing, damaged parts.

- Enough grease.

- No visible space between upper and lower fifth wheel.

- Locking jaws around the shank, not the head of kingpin.

- Release arm properly seated and safety latch/lock engaged.

• Fifth wheel (upper):

- Glide plate securely mounted to trailer frame.

- Kingpin not damaged.

• Air and electric lines to trailer:

- Electrical cord firmly plugged in and secured.

• - Air lines properly connected to glad hands, no air leaks, properly secured with enough slack
• for turns.

- All lines free from damage.

• Sliding fifth wheel:

- Slide not damaged or parts missing.

- Properly greased.

- All locking pins present and locked in place.

- If air powered–no air leaks.

• - Check that fifth wheel is not so far forward that tractor frame will hit landing gear, or cab hit
• the trailer, during turns.

(Page 7-4/7-5)

• UNCOUPLING TWIN TRAILERS
• UNCOUPLE REAR TRAILER

• Park rig in a straight line on firm level ground.

• Apply parking brakes so rig won't move.

• Chock wheels of second trailer if it doesn't have spring brakes.

• Lower landing gear of second semi-trailer enough to remove some weight from dolly.

• Close air shut-offs at rear of first semi-trailer (and on dolly if so equipped).

• Disconnect all dolly air and electric lines and secure them.

• Release dolly brakes.

• Release converter dolly fifth wheel latch.

• Slowly pull tractor, first semi-trailer and dolly forward to pull dolly out from under rear semitrailer.

UNCOUPLE CONVERTER DOLLY

• Lower dolly landing gear.

• Disconnect safety chains.

• Apply converter gear spring brakes or chock wheels.

• Release pintle hook on first semi-trailer.

• Slowly pull clear of dolly.

• ***Caution: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.***
• (Page 7-3)

A. Converter dolly air tank drain valve: CLOSED.

B. Make sure pintle hook is latched.

• DOUBLE AND TRIPLE TRAILERS
• • 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.

• Be sure air lines are supported and glad hands are properly connected.

• If spare tire is carried on converter gear (dolly), make sure it's secured.

• Be sure pintle-eye of dolly is in place in pintle hook of trailer(s).

• • Make sure pintle hook is latched.
• • Safety chains should be secured to trailer(s).

• Be sure light cords are firmly in sockets on trailers.

(Page 7-5)

A. Closed

B. Open

C. Closed

Read below for full explanation:

• DOUBLE AND TRIPLE TRAILERS
• • 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.
• • Be sure air lines are supported and glad hands are properly connected.

• If spare tire is carried on converter gear (dolly), make sure it's secured.

• Be sure pintle-eye of dolly is in place in pintle hook of trailer(s).

• Make sure pintle hook is latched.

• Safety chains should be secured to trailer(s).

• Be sure light cords are firmly in sockets on trailers.

Do these checks in addition to Section 5.3, "Inspecting Air Brake Systems."

(Page 7-5)

CHECK THAT AIR FLOWS TO ALL TRAILERS (Double and Triple 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. 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. Close the emergency line valve. Open the service line valve
• to check that service pressure goes through all the trailers (this test assumes that the trailer
• handbrake or the service brake pedal is on), then close the valve. If you do NOT hear air escaping
• from both lines, check that the shut-off valves on the trailer(s) and dolly(s) are in the OPEN position.
• You MUST have air all the way to the back for all the brakes to work.
• TEST TRACTOR PROTECTION VALVE
• Charge the trailer air brake system. (That is, 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.)
• If the tractor protection valve doesn't work right, 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.

• TEST TRAILER EMERGENCY BRAKES
• 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.

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.)

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