Rob Kirkham wrote:

A while ago I was able to make a trip into Sandon BC and take photos

and

measurements of the freight cars there. Now I'm writing a

description of

two of the cars. They were from the CPR 230000-233499 series

composite

boxcars - boxcars very much like the USRA design. And as I write

about

them, I wanted to say that when the cars were built in 1920-21, they

were

more or less the best boxcar design on the market.

But I wonder if that is really accurate? For example, would the

similar

cars used on other railways that used Z bracing (rather than the

pressed

steel shapes on the USRA and CP cars) be considered better or poorer

- or

was the difference inconsequential from the point of view of boxcar

design

evolution? Meanwhile, was there anything else on the market yet

that was

clearly superior?

--- In STMFC@..., "soolinehistory" Dennis Storzek replied:

Where are you saying these fit in the evolutionary chain, Rob? The

first steel frame boxcars used stock mill shapes, either Z, C, or L
section, while some of the last single sheathed composite cars did
likewise. The cars with the pressed framing fit in the middle, a good
idea that came... and went.

The argument for purpose designed pressings is they make more

efficient use of material, although I don't think the car designs that
made use of them were appreciably lighter.

The argument against purpose designed pressings was that they were

difficult to repair; the railroad would have to make custom pressing
dies to make replacement parts, whereas mill shapes were available off
the shelf, so to speak. Late in the cars lives it was found that the
pressings trapped water and tended to rust out near the bottom, but I
don't think this happened fast enough to really have any impact on the
debate; the cars lasted through a reasonable service life without major
problems. Anyway, cars with Z section framing also could have problems
with cracking of the posts and braces due to repeated stress reversals
in the truss members.

It appears that the two design philosophies coexisted for years

without either proving to be truly superior.

==========================

Looking at the the entire North American boxcar fleet we have the
eastern railroads, PRR, NYC and B&O that adopted the all steel designs
and were not large users of single-sheathed designs. So one could ask
the question was the all-steel designs superior to the single-sheathed
designs. Obviously for the mid-western, western and Canadian railroads
the single-sheathed design apparently better met their requirements.

Bob Witt