Tony Higgins wrote:

I have the RPCYC issue with your article and have studied the pictures and text but I'm still not sure what is meant by the term "spring plankless". What is a spring plank and what was it's purpose? From your response below, it seems somehow related to bolster/sideframe alignment and lateral stability? I can understand why this was a concern but how did spring planks address it? Can you please elaborate?

Tony, Richard is on his way to Cocoa Beach today and won't be replying, but I'll see if I can help. The spring plank was under the springs and ran across between the two sideframes, providing a second transverse connection in addition to the bolster. You can imagine how this helped keep the truck "square" -- and originally it really was a wooden plank. They became steel channels early in the 20th century.
When well-designed and machined sideframe-bolster connections came into use, constraining the sideframe movement to a vertical plane, the spring plank was no longer needed and could be dispensed with.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@...
Publishers of books on railroad history