Sir Richard Branson yesterday declared the driver of his crashed Virgin
train to be a hero for staying at his post and continuing to 'steer' the
Am I missing something? I was always under the impression that trains didn't
have steering wheels, and that their direction was determined by the track
and points. Further, that when they leave the track their trajectory is
determined purely by Newton's Laws of Motion - not by anything which the
driver might do.
Is this not correct?
On Sun, 25 Feb 2007 12:41:14 GMT, Harry Bloomfield
I think that puts the brakes on in a more controlled fashion but
It was explained on News 24 this morning that in an emergency the
driver operates a handle to pull the brakes on and then pulls another
handle but I can't recall exactly what that does .
They do, but you get more useful retardation if you apply the brakes
gradually and try to avoid the wheels locking up. This is particularly
important after a derailment, as a still-rolling derailed train is
_much_ safer than a derailed toboggan. It's quite likely that the driver
_did_ behave in a selfless and heroic manner to try and stop the train
sliding, which isn't recogised by Branson talking rubbish about
I don't know what happens if the emergency system on a Pendolino comes
into effect. They're disk braked, so a full application would lock the
wheels instantly. They're also fairly modern and sophisticated, so maybe
they still keep the anti-lock system effective, even in such a case.
It's not friction with the wheel that stops them, it's displacement of
the gravel as the wheels sink into it (and presumably gravel-on-gravel
It all comes down to heat in the end anyway, so I guess Branston's hot
air is just his attempt to help.
On Sun, 25 Feb 2007 16:16:12 -0000, "Tim.."
|!>>I thought trains had "dead man handle" brakes so they came on if the
|!>>let go of the handle anyway.
|!> They do, but you get more useful retardation if you apply the brakes|!> gradually and try to avoid the wheels locking up. This is particularly|!> important after a derailment, as a still-rolling derailed train is|!> _much_ safer than a derailed toboggan. It's quite likely that the driver|!> _did_ behave in a selfless and heroic manner to try and stop the train|!> sliding, which isn't recogised by Branson talking rubbish about|!> "steering"
|!> I don't know what happens if the emergency system on a Pendolino comes|!> into effect. They're disk braked, so a full application would lock the|!> wheels instantly. They're also fairly modern and sophisticated, so maybe|!> they still keep the anti-lock system effective, even in such a case.
|!The friction co-efficient of gravel when in contact with a cast wheel
|!intended for a track is going to be less than fuck all, so i'd be surprised
|!if it would stop at all locked wheels or not!!
Yes but the wheels flinging gravel around and digging trenches in it is
quite effective as braking. Think about gravel escape roads at the
bottom/middle of a hill, which are quite common in hilly areas.
Dave Fawthrop <dave hyphenologist co uk>
20,000 free e-books at Project Gutenberg! http://www.gutenberg.org
I've explained the mechanism of a derailment turning into a pile-up in
another post in this thread, which must have set some sort of record for
false information and ill-informed speculation.
Derailment investigation was my job for over ten years.
**Use current month and year to reply (e.g. firstname.lastname@example.org)***
On a car, the only effective difference between fully locked wheels and ones
just on the edge of locking is whether you retain steering or not. As
already pointed out, steering is not a consideration for trains.
On Sun, 25 Feb 2007 21:36:12 -0000, "nightjar".uk.com> wrote:
No, the "stopping power" of a locked wheel is much less than that of a
rolling one. So not only do you retain steering you also stop quicker.
Though I doubt this locked/rolling is particulary relevant in the case of
derailed train. As has already been pointed out it'll be the "gravel
trap" effect of a few hundred tonnes of train ploughing a course through
the ballast or track side trees/bushes/furniture that stops it.
I do have a slight problem with calling ballast "gravel" though. Ballast
is generally rough crushed stone in lumps around the 2" size. Gravel, to
me, tops out at less than inch.
Dave. pam is missing e-mail
The Metropolitan Police did a series of experiments that showed that the
difference between the stopping distance of a locked wheel and a rolling one
is minimal. The locked wheel is marginally better on a dry road. The rolling
wheel performs slightly better on a wet one. However, the differences would
not be significant in an emergency stop.
Given the appalling driving standards of the plods that doesn't surprise
me. No doubt they used a cross ply tyre on a transit van to prove their
The locked wheel is marginally better on a dry road.
The experience of every racing driver is that this is utter bollocks.
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