Re: Help needed for 1904 MDT reefers


Charles Peck
 

What you call humped is a condition often called hogged.  It would be normal in an unloaded car.
Weight in the middle of the car between the bolsters adds tension on the truss rods and compression
on the wooden frame. 
If you observe empty flatbed semitrailers you will see them arched or hogged so that they will
straighten when loaded.  Not uncommon to see bridges built the same way as they are stronger
in compression than in tension. 
Chuck Peck in FL

On Mon, Feb 13, 2017 at 11:13 AM, rwitt_2000@... [STMFC] <STMFC@...> wrote:
 

I assume this group of refrigerator cars are newly built. I am noticing that each underframes is "humped" I assume because the truss rods are over tighten. Was this the practice at the time? Are we to assume as the lumber dried and shrunk the underframe would settle into a more level position or did the car men make adjustments to the turnbuckles as the wood aged?

Many model sagging truss rod underframes, but I recall someone stating that "humped" underframes was a more common problem and rarely modeled..

Bob Witt


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