Re: 33 inch wheels

Kurt Laughlin <fleeta@...>

Maybe not the particular "Why?" you were looking for, but the analysis of contact stresses between two objects favors two flat surfaces touching each other. Failing that, with one surface flat (the rail) and the other not (the wheel), stresses are minimized and the load carrying capability maximized when the wheel is as large as possible. Rolling resistance is also reduced with larger wheels. The standard size nowadays is 36 inches, I think, but many double stack cars - like depressed center cars in the steam era - use 28 inch wheels to gain extra room for cargo under the clearance limits.

Why 33 rather than 32 or 34? I dunno, but they seem to have settled on that number very early on.


----- Original Message -----
From: snoqualmier

Why and when did the use of 33 inch wheels become standard on freight cars?

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