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Still, regardless of what is inside the shell, that is an amazing amount of movement. I suppose though that the actual expansion ratio though is probably expressed as a fraction of a percent?
All the things that go into engineering things. Like people not liking the old noise on trains as they go over the gaps in the rais for expansion (ANd them not being suited to high speed use) so now they weld them, and in the summer the risk is of railse expanding and going too far out of alignment (I have to use the term buckling)
Or just getting the cant of a bend wrong so that trains do not go through it at the natural speed of the bend and they either ride up or fall down the cant as they go around and wear out the wheel flanges on one side or the other. Which happened in Melbourne where both high speed commuter and slow freight trains use the same line, if you recall the wheel wear issue on the Ballarat trains.
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