In article , CJG
writes
Its been reported Virgin trains are being delayed up to 1 hour because
of National Rails headless chicken approach to a bit of sunshine.

Do you *ever* accept that somebody might know what they're doing when it
comes to running the railway? Or do you just like ranting nonsense?

In this case we're talking about basic physics. When you heat metal, it
expands. When you heat rails, they get bigger. That expansion has to go
somewhere.

Now back in the days of jointed rails you could put gaps between the
rails for them to expand into, but even then eventually the gaps filled.
With modern welded rail (providing a much smoother ride) you can't have
gaps. So, you anchor the rails firmly and install them so that they will
be at the right length when the temperature is 25 degrees C. If it gets
colder, they contract but the anchors pull on them, so the contraction
puts the rail under tension. If it gets hotter, they expand but again
the anchors pull on them and the rail goes under compression. Note that
the hotter it is, the more compression they are under.

If the rail is severely compressed *and* receives a severe blow at the
wrong point, the clips holding it on the sleepers and in line might not
be able to take the full force without giving way. Now the rail comes
free of the clip and buckles. This is clearly dangerous. So one thing
that can be done is to reduce the chances of a severe-enough blow, and
one way to do this is to reduce the speed of trains (track forces
increase with speed), particularly in areas at greatest risk.

On the run from King's Cross to Huntingdon last night there was *one*
emergency speed restriction - at the curve where the Hatfield derailment
happened. The rest of the run was at the usual 100mph. We were, IIRC, 3
minutes late overall (not just this one ESR; there are other longer-term
TSRs in place). This morning we've run normally as far as Stevenage,
which is where we are now.

--
Clive D.W. Feather, writing for himself | Home:
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