3.3. UNDERFRAME
The rail car underframe is the framework that receives the shock and
pulling stresses to which the car is subjected when it is being moved over
the railroad. It supports the deck and superstructure of the car and
carries the weight of the load in the car. Figure 3.1 shows the underframe
construction of a typical freight car, viewed from the bottom, to show the
body bolster center plates. What are the most important parts of the
underframe? They are the center sill, body bolsters, draft gear pockets,
side sills, end sills, and floor stringers; they are discussed in the
subparagraphs following.
Figure 3.1. Underframe.
a. The center sill is a longitudinal structural member that forms the
backbone of the underframe. It supports the other members of the underframe
and transmits the pushandpull stress
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