TM 55-203
CHAPTER 4
CAR TRUCK MAINTENANCE
Section I. GENERAL
also become so great as to make lateral movement of the
4-1. Types of Trucks
bearing and journal excessive for safe operation.
a. General. Car trucks have been generally
4-2. Maintenance of Truck as a Unit
described in paragraph 3-2. There are many different
types, but the same general characteristics are applicable
The body of a car may settle because of the wear of
to all This text is largely limited to the conventional, 4-
wheel treads, journals, bearings, and the possible
wheel, cast bolster, coil spring, side frame freight car
shortening of the springs resulting from set. This settling
truck (fig 3-1), discussed in paragraphs 4-19 through 4-21.
may be of vital importance since the relative height of the
settled car to other coupled cars is disturbed. However, a
b.
Inspection.
The inspection, repair, and
car can be brought up to proper level by placing shims or
maintenance of car trucks is an essential part of railway
liners of the required thickness under the truck springs or
operations, as the wheels must roll to move personnel,
by replacing the affected, weak springs. This will raise
equipment, and supplies by rail. Wheel flanges wear
the truck bolster and the body of the car. Cars also can
sharp, treads wear thin, and brakeshoes wear out. The
be raised by placing shims in the center plate. This
diameter of car wheel journals decreases and the length
requires compensating adjustment of side bearings. The
increases with service. Car journals wear down until they
proper height of a car can be established by measuring
are uneven or the journal finish reaches the danger point.
the height of the coupler from the rail level. This should
When this occurs, the defective surface must be
not exceed 34 1/2 inches (center of coupler) on CONUS-
smoothed and polished to create a new wearing surface.
type cars.
This wear and reconditioning eventually will reduce the
journal to an unsafe diameter and length. The length may
Section II. WHEEL AND AXLE ASSEMBLY
rim and flange resist expansion, cracks may develop in
4-3. General
the plate, rim, or flange because of the stresses they bear
at the time of brakeshoe application. Repeated cooling
a. Wheel Wear. Friction is the main cause of wear
and heating of the tread develops and increases the
on car wheels. This friction is developed by the contact of
number of cracks; frequently those cracks may result in
wheel with rail and by the contact of brakeshoes against
the fracturing or breaking off of sections of the rim or
wheel treads in braking Rail or rolling friction causes the
flange. Wear of the flanges against the outside rail of
greatest amount of wear, resulting in the development of
curves results in "sharp" flanges which are inherently
hollow spots in the tread next to the flange. These may
dangerous because such a sharp wheel may split a switch
be caused by high speeds, heavy loads, or unevenly
and cause a derailment.
jointed track. As noted, the friction of the brakeshoe
causes tread wear, but more important, the heat
b. Inspection. When the wheels and axles are
generated by brakeshoe application is gradually passed
removed from a truck for any reason, both wheels and the
on to the flange and rim of the wheel. The tread heats
axle should be thoroughly examined to ascertain whether
rapidly when the brakes are applied; therefore, the
other defects are present and
tendency is for the tread to expand out of proportion to
the rest of the wheel. Since the tread expands and the
4-1
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