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.

"Roger T." wrote
It's typical in North America to "power brake". In power
braking, the
throttle is left in notch two or three, the independent brake
in full
release while the train is brought to a stand with the train
brake
working
against the throttle. Is this not possible in the UK?

"Nev Arthur"
Not with the stuff I drive. Why would you do that?

To Keep the slack stretched. Remember, even North American
passenger trains
have slack. An inch or so in every coupling between each car.

Ah! See, you're talking to a passenger train driver here! I don't
know of all these tricks of the trade. On a Eurostar if you make
a brake application of more than just a bit, then the power gets
cut off. If the brake is slightly on, you cannot take power
either. That can cause much consternation when the driver hasn't
realised the brake is on slightly.
Nev

"Nev Arthur" wrote in
message ...
"Roger T." wrote
It's typical in North America to "power brake". In power braking, the
throttle is left in notch two or three, the independent brake in full
release while the train is brought to a stand with the train brake
working
against the throttle. Is this not possible in the UK?

"Nev Arthur"
Not with the stuff I drive. Why would you do that?

To Keep the slack stretched. Remember, even North American passenger
trains
have slack. An inch or so in every coupling between each car.

Ah! See, you're talking to a passenger train driver here! I don't know of
all these tricks of the trade. On a Eurostar if you make a brake
application of more than just a bit, then the power gets cut off. If the
brake is slightly on, you cannot take power either. That can cause much
consternation when the driver hasn't realised the brake is on slightly.
Nev

The wonderful traction interlock... Just make sure you don't get problems
with it on MY little railway, Nev- you b****** are bad enough when the snow
gets in the motors. What turns are you on at the moment ?
Brian

"Nev Arthur" wrote
Ah! See, you're talking to a passenger train driver here! I
don't know of all these tricks of the trade. On a Eurostar if
you make a brake application of more than just a bit, then the
power gets cut off. If the brake is slightly on, you cannot
take power either. That can cause much consternation when the
driver hasn't realised the brake is on slightly.

"BH Williams" wrote
The wonderful traction interlock... Just make sure you don't
get problems with it on MY little railway, Nev- you b****** are
bad enough when the snow gets in the motors. What turns are you
on at the moment ?

That's your fault, you keep the Tunnel too warm! ;-)
I'm on the Disney on Monday, 9074 I think, 09.39 out of WIT.
First one back into the UK on Tuesday, about 07.00 on your bit.
That's what's scheduled anyway.
Good luck to you and your colleagues, I know it's a bit miserable
there with the cuts and that. :-(
Nev

Upon the miasma of midnight, a darkling spirit identified as Roger T.
gently breathed:

Irrelevant. We know that with the brakes applied traction power
cannot be obtained.

Does this mean that any brake application automatically cuts traction power?

I believe the systems are set such that as soon as the brake pressure or
vacuum drops (or rises) beyond a certain point, power is automatically
cut and cannot be reapplied until the brake is restored.

It's typical in North America to "power brake". In power braking, the
throttle is left in notch two or three, the independent brake in full
release while the train is brought to a stand with the train brake working
against the throttle. Is this not possible in the UK?

I can see the advantages of this on very long freight trains, even with
continuous brakes there must be a lot of slack in a mile long train, but
your later post said it was common on passenger trains too - any idea
why? I don't see any advantage to it on something like an HST, where
the control layout ensures that brake valves open and shut
simultaneously at front and rear powercars, and there is no slack worth
speaking of in the 8 coach formations. Even in the days of 15 coach Mk1
rakes, it wasn't, AFAIK, possible. Possibly north American couplers
have more slack than UK ones do? The buckeyes fitted as standard from
Mk1 onwards are 3/4 scale copies of the US ones, though, and of course
until just a few years ago (and still, on railtour stock) the loco is
attached via screw-link over the drawhook with buffers extended to take
the compression.

Btw, what is the independent brake? We tend to have straight-air on
locos, and automatic air or automatic vacuum on the train.

--
- Pyromancer Stormshadow.
http://www.inkubus-sukkubus.co.uk -- Pagan Gothic Rock!
http://www.littlematchgirl.co.uk -- Electronic Metal!
http://www.revival.stormshadow.com -- The Gothic Revival.

On Thu, 11 Nov 2004 12:04:55 -0800, Roger T. wrote in
net.com, seen in
misc.transport.rail.europe:

Irrelevant. We know that with the brakes applied traction power
cannot be obtained.

Does this mean that any brake application automatically cuts traction power?

With the 3-step Westcode brake as fitted to Sprinters, any application
of step 2 or higher will automatically cause traction power to be cut
off.

HSTs have 7-step Westcode, so I can't say at which step power will be
cut off - but I'm happy to say that an emergency brake application
will result in traction power being cut off.

--
Ross Hamilton, in Lincoln (UK)
From address *will* bounce

"Pyromancer"

I can see the advantages of this on very long freight trains, even with
continuous brakes there must be a lot of slack in a mile long train, but
your later post said it was common on passenger trains too - any idea
why?

Because North American passenger trains have slack.

Also permits some leeway when travelling really slowly to a stop, you can
keep the train rolling without having to release the brakes to travel that
extra say 20 feet to the correct stopping point.

I used to power brake even with a trains of two passenger cars and even with
the doodlebug, a pre-war railcar. Mid you, in these cases it was power
braking with the throttle in notch one.


--
Cheers
Roger T.

Home of the Great Eastern Railway
http://www.highspeedplus.com/~rogertra/

In message , David Hansen
writes

Does this mean that any brake application automatically cuts traction power?

That is my understanding and it has been stated by others who are in a
position to know. Such an interlock appears to have been common since
the 1960s.
Not on the 6300s, 800s,1000s,7000s,9500s,1600s or any steam engine I
ever worked on.
--
Clive.

On Fri, 12 Nov 2004 01:12:56 +0000 someone who may be Clive Coleman
wrote this:-

Such an interlock appears to have been common since the 1960s.
Not on the 6300s, 800s,1000s,7000s,9500s,1600s or any steam engine I
ever worked on.

Were any of them designed in the late 1950s or 1960s?


--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
prevents me by using the RIP Act 2000.


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"Nev Arthur" wrote in
message ...
"Nev Arthur" wrote
Ah! See, you're talking to a passenger train driver here! I don't know
of all these tricks of the trade. On a Eurostar if you make a brake
application of more than just a bit, then the power gets cut off. If the
brake is slightly on, you cannot take power either. That can cause much
consternation when the driver hasn't realised the brake is on slightly.

"BH Williams" wrote
The wonderful traction interlock... Just make sure you don't get problems
with it on MY little railway, Nev- you b****** are bad enough when the
snow gets in the motors. What turns are you on at the moment ?

That's your fault, you keep the Tunnel too warm! ;-)
I'm on the Disney on Monday, 9074 I think, 09.39 out of WIT.
First one back into the UK on Tuesday, about 07.00 on your bit.
That's what's scheduled anyway.
Good luck to you and your colleagues, I know it's a bit miserable there
with the cuts and that. :-(
Nev

I'll listen out on the track-to-train for you..(early call both days, but
cover-only on the Monday)
Brian
Brian