TM 55-203
areas. The exceptions are those areas such as Korea,
welded to the center sills. These castings or lugs transmit
Japan, and China where AAR-type automatic couplers are
to the sills and the remainder of the car the stresses
used Neither hook-and-link nor Willison couplers transmit
received from the draft gear. Draft gears cushion the
buff directly to the center sill through draft gears. Buff
shocks between cars when they are being coupled or
loads are taken up by two side buffers at coupler height
when speed is suddenly changed. Instead of a shock,
above the top of the rail. Each buffer is set approximately
there is a gradually increasing push or pull against the car
35 inches off the longitudinal centerline of the car.
structure. These shocks are a result of the so-called run-
Design loads are fixed for both buffers and the hook and
in or run-out of slack purposely left in the couplers to
links of the coupler.
This design establishes the
permit a train to be started one car at a time. Original
maximum drawbar pull allowed when fixing train
draft gears were of the spring type. Modern cars,
tonnages, and the useful life of the coupler is directly
however, have either the spring type coupled with friction
related to the amount of misuse brought about by
devices to dampen the recoil that ordinarily accompanies
overloading. One of the outstanding characteristics of the
the release of a compressed spring or the recently
hook-and-link coupler is that the design provides for no
developed rubber-cushion type. (See chapter 6 for more
built-in slack between cars. Links are turned tight by
detailed discussion of draft gears.)
turnbuckles, thus losing all slack. These two coupling
devices are discussed and illustrated in chapter 7 One
3-7. Couplers, CONUS Cars
illustration, figure 7-6, depicts the side buffer
The coupler is the device which connects one car to
arrangement.
another, maintains the connection, and disconnects the
cars. The AAR type E coupler is standard on the railroads
3-9. Superstructure
of the United States for freight service Although some
Railway rolling stock superstructures include everything
cars built before 1933 are still equipped with type D
installed above the floor. As previously noted, flatcars
couplers, the type E coupler has been required on all cars
generally have no superstructures. Certain flatcars used
built since 1933. Two types of coupler shanks are
exclusively for moving logs in commercial service may
available, known respectively as the rigid shank and the
have end boards to keep the logs in place The
swivel-butt shank.
The swivel-butt shank permits
superstructure, or car body, is built upon the car
horizontal radial action by the coupler with respect to the
underframe. It is designed to fit a particular type of car
longitudinal centerline of the car. This arrangement is an
and purpose. Typical examples in common use include
advantage when coupling on curved track.
These
box, refrigerator, and tank cars, gondolas and hoppers,
couplers are discussed and illustrated in chapter 7.
coaches, kitchen and dining cars, ambulance, guard, and
sleeping cars. Superstructures include sides, ends, tops,
3-8. Couplers, Oversea Railway Equipment
roofs, seats, berths, tanks, etc., as applicable to the
With few exceptions, hook-and-link and Willison couplers
purpose of a particular type of car.
set at 41 inches coupler height predominate in oversea
3-3
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