>
>One of the major causes of delay on the California Zephyr is "heat
>restrictions" in the mountains. With higher temperatures, the rails
>lose their lateral stiffness* and the trains have to stay under 20 MPH
>(usually 15 MPH as they come down the eastern slope of the Rockies)
>going around all the twists and turns.
>
>* Rails are welded together while they are heated up to a certain
>temperature. This expands the rail segment being worked on. As it
>cools, it shrinks and tightens up. In the wintertime, the rails
>continue to shrink a bit and can pull sideways off the railbed in the
>mountains. In the summertime, at a certain temperature, the tightness
>is gone and the rails are neutralized. Above that temperature, they
>become looser and you'll get lots of wavies. This is why rails can be
>welded together without expansion joints--they are preheated to the
>expanded length at time of welding. A broken rail, that is under
>tension can do scary stuff to anything surrounding it.
>
There was a major derailment years ago in Florida where the welded rails
had warped. You will probably never hear of such a problem in Europe, where
the ends of the rails are chamfered, allowing for the expansion and contraction
over temperature. This is why you do not hear the characteristic "click-clack"
of US trackage. I think that Southern Railway adopted this design. My
understanding is that the chamfered end design originated in Germany.
Chris
When the going gets weird, the weird turn pro
- Hunter S. Thompson
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