TM 55-203
PART TWO
RAILWAY ROLLING STOCK
CHAPTER 3
BASIC COMPONENTS
tracking performance in service. The resemblance of
3-1. General
passenger-car trucks to those of freight cars is limited to
All railway rolling stock, of whatever type, generally will
similarity in function. High-speed operations necessitate
include six basic components, i.e., the trucks (wheels),
a type of truck for passenger cars which includes features
underframe, draft gear, brake gear, couplers, and
for the ,safety of :passengers in the event of abnormal
superstructure (body). There are exceptions. Flatcars
accidental impact, swing suspensions with vertical and
generally have no superstructure, and many cars in
lateral snubbing devices, and truck mounted brake
oversea areas are equipped only with handbrakes; some
cylinders and brake gear. Car trucks are discussed in
foreign cars, in fact, have no brakes at all. Other cars on
detail in chapter 4.
foreign railroads have hook-and-link couplings with a
buffer arrangement in lieu of an automatic coupler with a
3-3. Oversea Fleet Truck Parts
draft gear. The various car components are discussed
The truck parts of the Department of the Army (DA) 40-
separately with general and detailed inspection and
ton fleet differ in size from those of the 30-ton fleet.
maintenance procedures indicated as applicable.
However, truck parts within each fleet are identical and
interchangeable. For example, depot stocks of oversea
3-2. Trucks
truck side frames, bolsters, bolster springs, dust guards,
Truck is the term used to designate the wheeled assembly
journal bearings, wedges, etc., as well as wheels and
which, at each end of the car, supports the underframe or
axles, are identical -and interchangeable with the parts of
underframe and superstructure of a freight or passenger
all trucks or cars of equal capacities. The truck frame for
car. It may consist -of one, two, or more pairs of wheels.
the 40-ton fleet, except for the lightweight side frame and
Many European-type freight cars have only two pairs of
the chilled cast-iron wheels, which have been modified to
wheels (or bogies), one at each end. On most CONUS
meet operating conditions overseas, is similar to or is a
freight equipment, 4-wheel trucks (fig 3-1) are standard.
modification of truck components used on continental
Heavy-duty flatcars and passenger cars are usually
United States (CONUS) railways, and the wear limits and
equipped with 6-wheel trucks. A truck acceptable for
maintenance practices of CONUS railways are applicable.
service is flexible enough so that it rides without
interfering with other parts of the car, and its wheels follow
3-4. Wheels and Axles
curves in the track without climbing the rails to cause
possible derailment. Essential parts most likely to require
a. Wheels. Car wheels are of three general types:
repairs or replacement are readily accessible, and all
truck parts meet prescribed standards. Pedestal-type
cast iron, cast steel, and wrought steel. Cast-iron wheels
trucks and parts are today unusual in general-service
are no longer used by commercial railroads in CONUS,
freight equipment, except on trucks with roller bearings.
but are discussed herein because they are component
A passenger car truck assembly is designed to meet all
parts of the 30-ton and 40-ton oversea military car fleet
interlocking and structural requirements, provide proper
and are in service under Army-owned freight cars in
flexibility to insure free riding, and have good wheel-
oversea areas. Wrought steel wheels are generally
used under passenger cars.
3-1
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