Page 61 - 2021-2022 Commercial Drivers Manual

SECTION 7 : DOUBLES AND TRIPLES

Connect Converter Dolly to Front Trailer • Apply converter gear spring brakes or chock » Locking jaws around the shank, not the

wheels. head of kingpin.
• Back first semitrailer into position in front
of dolly tongue. • Release pintle hook on first semi-trailer. » Release arm properly seated and safety
latch/lock engaged.
• Hook dolly to front trailer. • Slowly pull clear of dolly.
• Check fifth wheel (upper).
• Lock pintle hook. Never unlock the pintle hook with the dolly » Glide plate securely mounted to trailer
still under the rear trailer. The dolly tow bar may frame.
• Secure converter gear support in raised po- fly up, possibly causing injury, and making it » Kingpin not damaged.
sition.
very difficult to re-couple.
Connect Converter Dolly to Rear Trailer • Air and electric lines to trailer.
7.2.3 – Coupling and Uncoupling » Electrical cord firmly plugged in and se-
• Make sure trailer brakes are locked and/or Triple Trailers cured.
wheels chocked. » Air lines properly connected to glad
Couple Tractor/First Semitrailer to Second/ hands, no air leaks, properly secured with
• Make sure trailer height is correct. (It must Third Trailers
be slightly lower than the center of the fifth enough slack for turns.

wheel, so trailer is raised slightly when dolly • Couple tractor to first trailer. Use the method » All lines free from damage.
is pushed under.) already described for coupling tractor-semi- • Sliding fifth wheel.
trailers. » Slide not damaged or parts missing.
• Back converter dolly under rear trailer. » Properly greased.
• Move converter dolly into position and cou-
• Raise landing gear slightly off ground to » All locking pins present and locked in
prevent damage if trailer moves. ple first trailer to second trailer using the place.
method for coupling doubles. Triples rig is » If air powered, no air leaks.
• Test coupling by pulling against pin of the now complete. » Check that fifth wheel is not so far forward
second semitrailer.
Uncouple Triple-trailer Rig that the tractor frame will hit landing gear,
• Make visual check of coupling. (No space or cab will hit the trailer, during turns.
between upper and lower fifth wheel. Lock- • Uncouple third trailer by pulling the dolly Landing Gear
ing jaws closed on kingpin.) out, then unhitching the dolly using the
method for uncoupling doubles. • Fully raised, no missing parts, not bent or
• Connect safety chains, air hoses, and light • Uncouple remainder of rig as you would any otherwise damaged.
cords.
double-bottom rig using the method already
• Close converter dolly air tank petcock and described. • Crank handle in place and secured.
shut-off valves at rear of second trailer (ser- • If power operated, no air or hydraulic leaks.
vice and emergency shut-offs). 7.2.4 – Coupling and Uncoupling Double and Triple Trailers
Other Combinations
• Open shut-off valves at rear of first trailer • Shut-off valves (at rear of trailers, in service
(and on dolly if so equipped). The methods described so far apply to the and emergency lines).
more common tractor-trailer combinations.
• Raise landing gear completely. » Rear of front trailers: OPEN.
However, there are other ways of coupling » Rear of last trailer: CLOSED.
• Charge trailer brakes (push “air supply” knob and uncoupling the many types of truck-trailer » Converter dolly air tank drain valve:
in), and check for air at rear of second trailer and tractor-trailer combinations that are in use. CLOSED.
by opening the emergency line shut-off. If air There are too many to cover in this manual.
pressure isn’t there, something is wrong and You will need to learn the correct way to couple • Be sure air lines are supported and glad

the brakes won’t work. and uncouple the vehicle(s) you will drive ac- hands are properly connected.
cording to the manufacturer and/or owner
7.2.2 – Uncoupling Twin Trailers specifications. • If spare tire is carried on converter gear
(dolly), make sure it’s secured.
Uncouple Rear Trailer
I
7.3 – nspecting Doubles • Be sure pintle-eye of dolly is in place in pintle
• Park rig in a straight line on firm level and Triples hook of trailer(s).
ground.
• Make sure pintle hook is latched.
• Apply parking brakes so rig won’t move. Use the seven-step inspection procedure de-
scribed in Section 2 to inspect your combina- • Safety chains should be secured to trailer(s).
• Chock wheels of second trailer if it doesn’t tion vehicle. There are more things to inspect • Be sure light cords are firmly in sockets on

have spring brakes.
on a combination vehicle than on a single ve- trailers.
• Lower landing gear of second semitrailer hicle. Many of these items are simply more of
enough to remove some weight from dolly. what you would find on a single vehicle. (For 7.3.2 – Additional Things to Check
example, tires, wheels, lights, reflectors, etc.) During a Walk-around Inspection
• Close air shut-offs at rear of first semitrailer However, there are also some new things to
(and on dolly if so equipped). Do these checks in addition to subsection 5.3,
check. These are discussed below.
• Disconnect all dolly air and electric lines and Inspecting Air Brake Systems.
secure them. 7.3.1 – Additional Checks
7.4 – Doubles/Triples
• Release dolly brakes. Do these checks in addition to those already Air Brake Check
listed in Section 2, Step 5: Do Walk-around In-
• Release converter dolly fifth wheel latch.
spection. Check the brakes on a double or triple trailer
• Slowly pull tractor, first semitrailer, and dolly Coupling System Areas as you would any combination vehicle. Sub-
forward to pull dolly out from under rear section 6.5.2 explains how to check air brakes
semitrailer. • Check fifth wheel (lower). on combination vehicles. You must also make
» Securely mounted to frame.
Uncouple Converter Dolly the following checks on your double or triple
» No missing or damaged parts. trailers
• Lower dolly landing gear. » Enough grease.
» No visible space between upper and lower
• Disconnect safety chains.
fifth wheel.
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