Dennis Storzek wrote:

Is it too late for me to chime in here? "Diaphragm" is a fabricator's term, possibly now archaic, for a web that spaces structural members. Used in this manner, any built-up bolster consists of four pressed steel diaphragms, top and bottom cover plates, a center filler and possibly end fillers. The usage of the term is correct, but hardly unique to the Standard Tank Car Co. bolsters.

So if I understand your comment, Dennis, a bolster built up of pieces called diaphragms can be called a "diaphragm." By the same logic, since it's riveted together with rivets, I can call it a "rivet" also. I would suggest that this example of calling the whole by the name of some of its parts is NOT a very sound usage and certainly risks being misleading.

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