Re: Time Periods for Different Truck Types

Bob Karig <karig@...>

The spring plank was used to hold the two side frames together. It ran between the two side frames beneath the bolster. The springs sat on the spring plank and the bolster sat on top of the springs. The bolster rode up and down on the springs and was held in place by the column guides.

With spring plankless trucks, the spring plank was removed and the column guide/bolster interface was designed to hold the trucks in alignment in much the same way that scale trucks are held in alignment.

One of the problems with the spring plank was that it held the two side frames too rigidly together. The twisting stress on the truck as it entered turns caused the joint to loosen and allow the trucks to move out of alignment. With the spring plankless/self aligning truck, the truck was allowed to flex going into a turn and return to its normal alignment on straight track.

Bob Karig

At 01:27 PM 1/2/2008, you wrote:
--- In STMFC@..., Richard Hendrickson <rhendrickson@...>
Thanks for your typically thorough answer. 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 Higgins

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