4.4. CROSSBEARERS AND CROSSTIES
The crossbearers are heavy transverse members between the two body bolsters. They tie the side sills to
the center sill, stiffen the structure, and help to distribute the weight of the car and lading. Some crossbearers
extend from one side sill to the other, and these have fillers between the two beams that form the center sill.
Because of the thickness of the crossbearers, holes are usually drilled in them on either side of the center sill so
that airbrake and steam lines can pass through them. However, some freight car underframes have angle iron
brackets either riveted or welded on to various parts of the underframe to secure these lines. An example of this
kind of construction is shown in the welded-steel underframe in figure 4.1.
Crossties differ from crossbearers in size. They are smaller and lighter, and they connect the side sills to
the near side of the center sill. Crossties do not extend from one side sill to the other. They are sometimes
called stringer supports.
4.5. FLOOR STRINGERS
The floor stringers are longitudinal members located between the center sill and the side sills. They
usually run the length of the car between the end sills, and the flooring of the car is attached to them. Secured
to all transverse members, they strengthen the framework. Although they occupy the same positions as sills,
they are not designed to function as sills.
4.6. STRIKER PLATES AND SAFETY ATTACHMENTS
To protect the draft gear and the center sill, striker plates are welded or riveted around the coupler opening
in the end sills. The coupler horn strikes these plates when the car is being coupled to another car.
To protect operating personnel from injury, several safety attachments are placed on the underframe.
These attachments are discussed separately in chapter 7.
4.7. SUMMARY
The two principal types of railway car underframes are of riveted and welded-steel construction. Both
types consist of several different members that vary in size and strength depending
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