Tony Bryer wrote in message ...
This is not my specialist subject, but surely it is the case
that the crumpling up makes them safer. Wasn't it the case that
a number of rail crashes a while back were made much worse
because the carriages were built off incompressible underframes
and so rode up violently in a collision?

I think its the old stock with bodies built on frames rather than
monocoque construction where that occurs. I'm not sure crumple zones
on carraiges are a terribly good idea since in the rush hour a dozen
people or more might be standing in the bit that crumples besides which
in a major accident carraiges tend to go all over the place and don't
always impact head on with whatever they hit. Better to make the whole
design strong so that it doesn't fly apart and hope for the best I would
have thought. Besides , if you're doing 125mph or even 180mph in a eurostar
and theres an accident I doubt a few feet of crumple zone would make a blind
bit of difference.

B2003

Ed Crowley wrote:
"Boltar" wrote in message
om...
Robin May wrote in message
...
Are you stupid? A train is several times longer than a car or bus
and even more times heavier.

No **** sherlock. And consequently they should be built a damn site
stronger than road vehicles. Obviously this is not the case, at
least not for tube trains. If any vehicle crumples up at such a low
speed it doesn't say a lot thats good about the design. Perhaps they
should have used the same team who designed the mainline mk3,
probably one of the safest vehicles on wheels.

It's entirely sensible for trains to crumple on impact, to absorb
some of the force of the collision.

But the front of the derailed car at Camden Town was destroyed rather than
crumpled. Photo at http://news.bbc.co.uk/1/hi/england/london/3227365.stm
This may have been because it hit the wall at an angle rather than head-on.
--
Richard J.
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(Boltar) wrote the following in:
om

Robin May wrote in message
...
Are you stupid? A train is several times longer than a car or bus
and even more times heavier.

No **** sherlock. And consequently they should be built a damn
site stronger than road vehicles. Obviously this is not the case,
at least not for tube trains. If any vehicle crumples up at such a
low speed it doesn't say a lot thats good about the design.
Perhaps they should have used the same team who designed the
mainline mk3, probably one of the safest vehicles on wheels.

I think it did pretty well considering it had God knows how many tons
travelling at 15mph forcing it in to the wall.

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Ed Crowley wrote:
It's entirely sensible for trains to crumple on impact, to absorb some of
the force of the collision.

Isn't that what the couplings are supposed to do?

Rigid coaches linked by squishy bits sounds good to me

Colin McKenzie
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On Thu, 30 Oct 2003 16:07:42 GMT, "Richard J."
wrote:

But the front of the derailed car at Camden Town was destroyed rather than
crumpled. Photo at http://news.bbc.co.uk/1/hi/england/london/3227365.stm
This may have been because it hit the wall at an angle rather than head-on.

Probably. One of the fundamental weaknesses of a metal tube of any
kind (or indeed a bog roll tube if you want to try it out yourself!)
is that, while it can take a massive end loading without buckling, a
small side loading is sufficient to cause major deformation. Without
returning to compartment stock (obviously not practicable on the
Tube), this will always be the case regardless of strengthening.

How the Mark 3 and aluminium Turbo stock performed (or did not) in
recent HST crashes is a good comparison. Compress the HST stock
end-on and it's fine. If one vehicle jack-knifes, it'll likely end up
in a far worse way.

The other issues, of course, are that Tube trains travel much more
slowly - and in the majority of cases (e.g. Chancery Lane) will stay
in line simply by virtue of the fact that the tunnel is but a few
inches away on each side, so collisions at an odd angle are rare.
This must surely impact on the design.

Neil

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