Transcript Chapter 33 Heavy-duty Truck Trailers

Chapter 33
Heavy-duty Truck Trailers
Objectives (1 of 2)
• Describe what is meant by semi-trailers and
full trailers.
• Identify the various different tractor/trailer and
train combinations.
• Describe what is meant by full frame,
unibody, and monocoque.
• Explain the various types of hitching
mechanisms used and their effects on
tractor/trailer or train designation.
Objectives (2 of 2)
• Describe the design characteristics of the dry
van, reefer, flatbed, tanker, and other types of
highway trailer.
• Explain the operating principles of a reefer
trailer.
• Outline some common trailer maintenance
practices.
Types of Trailers
Semi-trailer
B-Train
Full Trailer
A-Train
Converter Dolly
Gooseneck
Unibody
C-Train
Cargo Vans
Reefer (1 of 2)
Reefer (2 of 2)
Flat-Bed
Dump Trailers
Tankers
Shop Talk
• For optimum brake performance and safety, both
wheel ends of each axle must have the same type
of lining and drum equipment.
• If the trailer has tandem axles, both axles must also
have the same type of wheel equipment.
• The vehicle brake-lining thickness must be the
same on each brake shoe and on each side of the
axle.
• When brake linings are 1/4 inch in thickness or less
at their thinnest point, they should be replaced.
Shop Talk
• One of the weight-savers now being used as
an option by some trailer OEMs is fiber
composite springs
• They can save up to 50 pounds per spring,
and can outlast steel springs.
• Although the initial cost is around four times
that of steel springs, they can last the life of
the trailer, so they are ultimately, an
economical choice.
Landing Gear
Trailer Lighting (1 of 2)
Trailer Lighting (2 of 2)
• See Table 33-1 on page 1092 of textbook.
Reflective Tape
Shop Talk
• The entire body shell in a unibody van trailer
is the frame. If any body component is
damaged the structural integrity of the frame
is at risk.
• A slightly damaged floor or out-of-square
doorframe can be an indication of a much
more serious problem.
Caution
• High modern power wash equipment can
produce high impact water jets.
• Take care when using it on trailer panels and
tanker skins because it can indent or cause
abrasive damage.
Summary (1 of 6)
• A semi-trailer is a trailer in which a portion of the
trailer weight is supported by the tow unit— either a
tractor or a lead trailer.
• A full-trailer is any trailer in which the trailer weight
is self-supported and the unit is towed by a tractor
or lead trailer by means of a hook and drawbar
assembly.
• A semi-trailer can be converted to a full-trailer by
means of a converter dolly.
• A train is a combination of a tractor and multiple
trailers.
Summary (2 of 6)
• An A-train double consists of a tractor, semilead trailer, and full-pup trailer.
• A B-train double consists of a tractor, semilead trailer, and semi-pup trailer.
• A C-train double uses a rigid double drawbar
and converter dolly to attach the pup trailer.
• Many van trailers use a unibody or
monocoque frame.
Summary (3 of 6)
• A unibody frame is essentially a shell in which all of
the shell components play a role in the frame
dynamic, including the floor, side panels, bulkhead,
doors, and roof.
• The van trailer is the most common truck trailer on
North American roads.
• There are two ways to obtain light weight without
sacrificing strength.
– One is by using lighter, more expensive materials
such as aluminum and high-strength steel in posts
and crossmembers.
– The other is to use wall posts and floor crossmembers that have a deeper section.
Summary (4 of 6)
• A 1-inch increase in the width of a 53-foot
trailer often makes the difference between
getting two pallets side by side or not.
• Freight vans are probably the most widely
used trailer model in operation.
• Modern refrigerated trailers or insulated vans
are dry freight vans that are completely
insulated and have a reefer unit usually
located at the front or nose of the trailer.
Summary (5 of 6)
• In addition to vans, there are several trailer types
and designs.
– One of the most common types is the platform or
flatbed trailer.
• The number of axles and tires used with each trailer
design depends on the rated load it is intended to
carry.
• There are two basic designs of tank trailers: liquid
(wet) haulers and dry-bulk haulers.
• Landing gear damage often results from driver and
yard jockey abuse especially during coupling and
uncoupling.
Summary (6 of 6)
• Trailer wheel and tire designs are generally
interchangeable between tractors and trailers.
• Trailer slide tandems allow the load bridge formula
to be altered; they increase flexibility,
maneuverability, and ability to meet weight laws.
• Trailers must be serviced on regular preventive
maintenance schedules: service schedules may be
based on hubdometer mileage or in applications
that are used intermittently, by calendar.