a. Full Trailer. Full trailers may be classified as
the fifth wheel on a dolly (fig. 38-8) and using the dolly In
place of a tractor as the semitrailer front end support.
nonreversible, reversible, and converted semitrailers.
This combination is known as a converted semitrailer.
A nonreversible full trailer can be towed and steered
The dolly is a short two-wheel trailer chassis with a
from one end only. Its frame is supported by front and
standard lower fifth wheel mounted on its frame.
rear two-wheel trucks that consist of a square frame
made of channel sections containing the spring hangers.
The front end of its frame is tapered to receive a bracket
The rear truck is bolted to the trailer frame and forms an
that contains a lunette for towing the trailer by a pintle
Integral part of the chassis. A lower fifth-wheel ring
assembly. A retractable landing gear supports the front
mounted on top of the front truck fits together with an
end of the dolly when not in use. The open hooks on
upper fifth-wheel ring attached underneath the front end
either side at the front end of the frame are used for
of the trailer frame. The front truck, therefore, turns
Joining the towing vehicle and the trailer with safety
around the fifth wheel, which allows the trailer to be
steered. A towing tongue is pivoted to the front truck,
and the other end contains a lunette that connects with
The rear-end view of a heavy-duty vehicle (fig. 38-9),
the pintle hook of the towing vehicle. The trailer chassis
used for towing three-quarter and full trailers, Illustrates
Illustrated In figure 38-7 is equipped with electrical and
the pintle assembly. The rear bumpers protect the frame
airbrake connections, which are hooked up to the towing
of the vehicle and guide the trailer lunette (towing hook)
vehicle. A safety chain is provided to prevent the trailer
into the pintle assembly during the trailer coupling
from running away if the pintle hook connection should
operation. The electric brake lead of the trailer is
plugged Into the electric brake connection, shown with
the cover open. The airbrake connections enable the
A reversible full trailer may be towed or steered from
airbraking system of the towing vehicle to be Joined to
either end. It is similar to the nonreversible trailer In
that of the trailer when the trailer is equipped with
construction and appearance, except that both front and
alrbrakes. The alrbrake connection is shown with Its cap
rear trucks are mounted by fifth wheels. The towing
removed, as It would appear when ready for coupling.
tongue is detachable and may be used with either truck.
Both trucks are provided with locks so that one may be
prevented from turning when the other is connected to
38-10. Drawbar and Lunette. The drawbar and lunette
the towing ends, thus Increasing the operating flexibility
used on full trailers are similar to those used on three-
of the trailer.
quarter trailers described In paragraphs 38-6 and 38-7.
b. Semitrailer Converted to a Full Trailer.
semitrailer may be converted to a full trailer by mounting
Figure 38-7. Typical Full-Trailer Chassis.