-
1. What is a converter dolly?
- 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)
-
2. Do converter dollies have spring brakes?
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)
-
3. What three methods can you use to secure a second trailer before coupling?
- 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)
-
4. What do you check when making a visual check of coupling?
- 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)
-
5. Why should you pull a dolly out from under a trailer before you disconnect it
from the trailer in front?
- 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)
-
6. A. What should you check for when inspecting the converter dolly?
B. The pintle hook?
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)
-
7. A. Should the shut-off valves on the rear of the last trailer be open or closed?
B. On the first trailer in a set of doubles?
C. On the middle trailer in a set of triples?
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)
-
8. How can you test that air flows to all trailers?
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.)
(Page 7-5/7-6)
|
|