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7.3 Inspecting Doubles and Triples

The methods described thus far apply to the more common tractor-trailer combinations. However, there are other ways of coupling and uncoupling the many types of truck-trailer and tractor-trailer combinations in use. There are too many to cover in this manual. Learn the correct way to couple the vehicle(s) you will drive according to the manufacturer and/or owner.

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 shank, not head of kingpin.
  • Release arm properly seated and safety latch/lock engage.
Fifth wheel (upper):
  • Glide plate securely mounted to trailer frame.
  • Kingpin not damage.
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 of 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.
  • Fifth wheel is not so far forward that tractor frame will hit landing gear or cab will hit the trailer during turn.
Landing gear:
  • Fully raised, no missing parts, not bent or otherwise damaged.
  • Crank handle in place and secured.
  • If power operated, no air or hydraulic leak.

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
  • Air lines supported and glad hands properly connected.
  • If spare tire is on converter gear (dolly), make sure it is secured.
  • Pintle-eye of dolly in place in pintle hook of trailer(s).
  • Pintle hook latched.
  • Safety chains secured to trailer(s).
  • Light cords firmly in sockets on trailer.

CDL:

Commercial Driver's License (CDL)

A CDL is required to drive any of the following vehicles:

  • Any combination of vehicles with a gross combined weight rating (GCWR) of 26,001 or more pounds, providing the gross vehicle weight rating (GVWR) of the vehicle being towed is in excess of 10,000 pounds.
  • Any single vehicle with a GVWR of 26,001 or more pounds, or any such vehicle towing another not in excess of 10,000 pounds.
  • Any vehicle, regardless of size, designed to transport 16 or more persons, including the driver.
  • Any vehicle required by federal regulations to be placarded while transporting hazardous materials.

Doubles:

Refers to pulling two trailers at the same time, otherwise known as "pups" or "pup trailers" because they're only about 28 feet long. However there are some states that allow doubles that are each 48 feet in length.

Review Questions - Click On The Picture To Begin...

When making a visual check of the coupling, all of the following inspections are correct, except:
  • Check that there is no visible space between the upper and lower fifth wheel
  • Make sure there is enough grease
  • Ensure the release arm is properly seated and the safety latch is unlocked
  • Be certain the locking jaws are around shank and not the head of the kingpin

Quote From The CDL Manual:

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 shank, not head of kingpin
  • Release arm properly seated and safety latch/lock engaged

Check Fifth wheel (upper)

  • Glide plate securely mounted to trailer frame
  • Kingpin not damaged
Next
Which of the following shut off valve positions is incorrect?
  • Converter dolly air tank drain valve: CLOSED
  • All of these are correct
  • Rear of front trailers: OPEN
  • Rear of last trailer: CLOSED

Quote From The CDL Manual:

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
  • Air lines supported and glad hands properly connected
  • If spare tire is on converter gear (dolly), make sure it is secured
  • Pintle-eye of dolly in place in pintle hook of trailer(s)
  • Pintle hook latched
  • Safety chains secured to trailer(s)
  • Light cords firmly in sockets on trailers
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Page 57:
Coupling And Uncoupling Triple Trailers
Page 58
Page 59:
Doubles And Triples Air Brake Check

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