On Wed, 10 Nov 2004 09:09:38 -0800, S.Byers wrote:

The extent of the damage in the Berkshire crash was caused by ...
1/ the rear power car, still under full power,

FO back under your stone, troll.

In message , A.Lee
writes
On Wed, 10 Nov 2004 09:09:38 -0800, S.Byers wrote:

The extent of the damage in the Berkshire crash was caused by ...
1/ the rear power car, still under full power,

FO back under your stone, troll.

I don't troll this N/G but I do remember working on British Railways
when propelling was not allowed above 40mph. I expect I'll now get
some egghead to troll me, but this was always the case when working
tender first. (It also had the advantage of keeping the coal dust out
of your eyes).
--
Clive.

Clive Coleman schrieb:

I don't troll this N/G but I do remember working on British Railways
when propelling was not allowed above 40mph. I expect I'll now get
some egghead to troll me, but this was always the case when working
tender first.

I guess the tenders didn't like speeds similar to 100 mph while running
first. However, they managed to order trains without tenders.

Secondly, there was a power car in front of the train when it hit the
obstacle.

Regards, ULF

"Clive Coleman" wrote in message
...
In message , A.Lee
writes
On Wed, 10 Nov 2004 09:09:38 -0800, S.Byers wrote:

The extent of the damage in the Berkshire crash was caused by ...
1/ the rear power car, still under full power,

FO back under your stone, troll.

I don't troll this N/G but I do remember working on British Railways
when propelling was not allowed above 40mph. I expect I'll now get
some egghead to troll me, but this was always the case when working
tender first. (It also had the advantage of keeping the coal dust out
of your eyes).
--
Clive.

Braking and power control not withstanding, a heavy weight at the rear of a
train is not good news when it has to stop in a hurry, but a heavy weight at
the front means a better chance of staying upright and, potentially, more
protection for the guy at the sharp end.

On Wed, 10 Nov 2004 21:08:02 -0000 someone who may be "Tim
Christian" wrote this:-

Braking and power control not withstanding, a heavy weight at the rear of a
train is not good news when it has to stop in a hurry,

The "heavy weight" is equivalent to two or three coaches. Nobody
worries about the effect in a crash if two or three coaches are
added to a train.



--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
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In article ,
Tim Christian wrote:

"Clive Coleman" wrote in message
...
In message , A.Lee
writes
On Wed, 10 Nov 2004 09:09:38 -0800, S.Byers wrote:

The extent of the damage in the Berkshire crash was caused by ...
1/ the rear power car, still under full power,

FO back under your stone, troll.

I don't troll this N/G but I do remember working on British Railways
when propelling was not allowed above 40mph. I expect I'll now get
some egghead to troll me, but this was always the case when working
tender first. (It also had the advantage of keeping the coal dust out
of your eyes).
--
Clive.

Braking and power control not withstanding, a heavy weight at the rear
of a train is not good news when it has to stop in a hurry, but a heavy
weight at the front means a better chance of staying upright and,
potentially, more protection for the guy at the sharp end.


The momentum of one loco at the back is no different from three coaches at
the back (approx). So its one coach trains only from now on ?

David

Tim Christian wrote:

Braking and power control not withstanding, a heavy weight at the rear of a
train is not good news when it has to stop in a hurry,

It makes absolutely no difference what the distribution of weight in the
train is when stopping in a hurry. The suggestion that the locomotive in
the rear is somehow a problem demonstrates a complete misunderstanding
of the physics involved.

The issue is the total mass of the train behind a derailed vehicle,
which includes the mass of the coaches as well as the power car. That
total mass is what creates the tendency to jackknife. The only way to
avoid it is to run separate, individual vehicles, since there would then
be nothing to push from behind. Individual vehicles are what run on
highways. Trains run on tracks.

but a heavy weight at the front means a better chance of staying
upright and, potentially, more protection for the guy at the sharp end.

That is true, since a heavy vehicle is more likely to remain on the
rails, rather than be lifted up in a collision and derail. However, just
because a vehicle is heavy doesn't necessarily mean that it offers more
protection. I acknowledge that you said "potentially", since the weight
can be from other things than extra strength applied to the front
structure of the vehicle, which would provide the necessary protection.

In message , James Robinson
writes
That
total mass is what creates the tendency to jackknife. The only way to
avoid it is to run separate, individual vehicles, since there would then
be nothing to push from behind. Individual vehicles are what run on
highways. Trains run on tracks.


Don't say that too loudly otherwise the media and safety mafia will be
screaming for all real trains to be replaced by dogboxes! :-)
--
Spyke
Address is valid, but messages are treated as junk. The opinions I express do
not necessarily reflect those of the educational institution from which I post.

James Robinson writes:
It makes absolutely no difference what the distribution of weight in the
train is when stopping in a hurry. The suggestion that the locomotive in
the rear is somehow a problem demonstrates a complete misunderstanding
of the physics involved.

The issue is the total mass of the train behind a derailed vehicle,
which includes the mass of the coaches as well as the power car. That
total mass is what creates the tendency to jackknife.

Er, this is why it *does* make a difference.

If a passenger car weighs P tons, and a locomotive weighs L tons
(where L P), then moving a single locomotive from the front to
the rear increases the total weight behind the Kth vehicle from the
front of the train by L-P tons; and it increases the total weight
behind the Kth passenger car by L tons.

It is one thing to decide that this difference does not pose enough
additional risk to offset the operational benefits; it is quite another
to say that it makes "absolutely no difference" and throw around words
like "complete misunderstanding" while disproving your own point.

Another issue is whether the heavier locomotive or the lighter passenger
cars would be more likely to derail in any particular situation. If one
type of vehicle is more likely to derail, putting it at the front is a
less safe choice. But I think this would depend on the particular mode
of derailment, and probably on the suspension characteristics of the
individual models; it's not obvious which is the best choice on this
basis, or, again, whether it makes enough difference to offset matters
of operational benefit.
--
Mark Brader, Toronto "As long as that blue light is on, the
computer is safe." -- Hot Millions

My text in this article is in the public domain.

Mark Brader wrote:

James Robinson writes:

It makes absolutely no difference what the distribution of weight in the
train is when stopping in a hurry. The suggestion that the locomotive in
the rear is somehow a problem demonstrates a complete misunderstanding
of the physics involved.

The issue is the total mass of the train behind a derailed vehicle,
which includes the mass of the coaches as well as the power car. That
total mass is what creates the tendency to jackknife.

Er, this is why it *does* make a difference.

If a passenger car weighs P tons, and a locomotive weighs L tons
(where L P), then moving a single locomotive from the front to
the rear increases the total weight behind the Kth vehicle from the
front of the train by L-P tons; and it increases the total weight
behind the Kth passenger car by L tons.

My response was hyperbole, to some extent. I was addressing the
descriptions in the press that focus on the big nasty power car at the
rear of the train, and ignore the fact that the leading carriage had 7
other carriages behind it in addition to the power car.

The power car was not some sort of juggernaut that pushed everything
ahead of it hither and yon, only additional mass that adds to the
momentum behind the leading carriage. To suggest otherwise is to
suggest that trains made up of anything in excess of 8 or 9 carriages
is somehow unsafe.

It is the very essence of what a train is -- a series of vehicles
coupled together. To ascribe the extent of the derailment solely to
the fact that a power car is marshalled at the rear, which some
reports did, demonstrates a misunderstanding of the physics.

Does it mean that the mass from additional carriages are somehow
better than the equivalent mass of a power car? Should trains be
limited in length to a maximum of two carriages, since the additional
mass of one more carraige behind the leading one would cross a
threshold of safety and become unsafe? Would those who advocate the
removal of the trailing power car reverse their views after a tail-end
collision and demand the additional protection of the power car again?

It is one thing to decide that this difference does not pose enough
additional risk to offset the operational benefits; it is quite another
to say that it makes "absolutely no difference" and throw around words
like "complete misunderstanding" while disproving your own point.

The media reports, plus those of many posters to this group
demonstrate a complete misunderstanding of the physics, and ascribe
far more risk to the operation of locomotives at the rear of trains
than is reality.

However, let me rephrase my original statement to reduce the
controversy: Given the many factors involved in collisions and
derailments, the effect of placing a power car at the rear of the
train on the severity of the resulting accident, in comparison to
other factors, is so small as to be inconsequential, or presents no
greater risk than other generally accepted operating practices. Is
that run-on sentence mushy enough?