The Equalizer wrote:
"Acrosticus" wrote in message
...
From: Michael Bell
Date: 08/08/2003 23:43 GMT Daylight Time

It has always seemed to me that the 750 volt 3rd rail is
a bad
idea.

Too right! Massive amperages, high resistances, huge
numbers of substations in relation to the length of a
line. It's an idea that's really past its sell by date. If
you want to electrify, do it properly with 25Kv at 50
Hertz in a wire up on some sticks. Tinkering about with
750v DC is about as much good as rearranging the
deckchairs on the deck of the "Titanic".



And as soon as we get some windy weather all the overhead
lines come down and the entire rail network is screwed.

Not all, just that which was put up on the cheap.

"Cast_Iron" wrote in message
...
The Equalizer wrote:
"Acrosticus" wrote in message
...
From: Michael Bell
Date: 08/08/2003 23:43 GMT Daylight Time

It has always seemed to me that the 750 volt 3rd rail is
a bad
idea.

Too right! Massive amperages, high resistances, huge
numbers of substations in relation to the length of a
line. It's an idea that's really past its sell by date. If
you want to electrify, do it properly with 25Kv at 50
Hertz in a wire up on some sticks. Tinkering about with
750v DC is about as much good as rearranging the
deckchairs on the deck of the "Titanic".



And as soon as we get some windy weather all the overhead
lines come down and the entire rail network is screwed.

Not all, just that which was put up on the cheap.



Network Rail = Cheap

"The Equalizer" wrote in message
...

"Cast_Iron" wrote in message
...
The Equalizer wrote:
"Acrosticus" wrote in message
...
From: Michael Bell
Date: 08/08/2003 23:43 GMT Daylight Time

It has always seemed to me that the 750 volt 3rd rail is
a bad
idea.

Too right! Massive amperages, high resistances, huge
numbers of substations in relation to the length of a
line. It's an idea that's really past its sell by date. If
you want to electrify, do it properly with 25Kv at 50
Hertz in a wire up on some sticks. Tinkering about with
750v DC is about as much good as rearranging the
deckchairs on the deck of the "Titanic".



And as soon as we get some windy weather all the overhead
lines come down and the entire rail network is screwed.

Not all, just that which was put up on the cheap.



Network Rail = Cheap

Network Rail = Expensive
Railtrack = Less Expensive
British Rail = Cheap

are (Acrosticus) wrote in message ...
From: Michael Bell
Date: 08/08/2003 23:43 GMT Daylight Time

It has always seemed to me that the 750 volt 3rd rail is a bad
idea.

Too right! Massive amperages, high resistances, huge numbers of substations in
relation to the length of a line. It's an idea that's really past its sell by
date. If you want to electrify, do it properly with 25Kv at 50 Hertz in a wire
up on some sticks. Tinkering about with 750v DC is about as much good as
rearranging the deckchairs on the deck of the "Titanic".

OTOH hand , when was the last time that you heard of trains being stuck or
cancelled because the 3rd rail fell over? There doesn't seem to be a winter
that goes by without some AC line being screwed by snapped overhead wires.
Catenary is fragile and flakey and is a terrible design plus it looks bloody
awful too. The only place its really needed is street based tramways.

What is needed is some sort of mid voltage (maybe 3000-6000V) sturdy ground
based 3rd rail system which isn't as fragile as overhead wires but doesn't
have the power losses of standard 750V 3rd rail. I'm sure isn't beyond the wit
of man to devise it.

B2003

In article ,
Boltar wrote:
OTOH hand , when was the last time that you heard of trains being stuck or
cancelled because the 3rd rail fell over?

Sometime around last year, around Bank. I can't remember the
details, but I think the central conductor rail "fell over", rather
than the outer one.

(OK: so it was trains being stuck/delayed/canceled because the 4th
rail fell over, rather then the 3rd. And it was a rather unusual
incident.)


--
Good night little fishey-wishes.... I've counted you, so no
sneaky eating each other.
-- FW (should I worry?)

"Mike Bristow" wrote in message
...
In article ,
Boltar wrote:
OTOH hand , when was the last time that you heard of trains being stuck
or
cancelled because the 3rd rail fell over?

Sometime around last year, around Bank. I can't remember the
details, but I think the central conductor rail "fell over", rather
than the outer one.

(OK: so it was trains being stuck/delayed/canceled because the 4th
rail fell over, rather then the 3rd. And it was a rather unusual
incident.)


Happened to the pozzie at Wood Green about 7 years ago, IIRC the LUL jargon
for such an incident is "Turned Juice Rail"
--
Cheers, Steve.
If The Good Lord had meant for us to be fiscally prudent, He would not have
given us the platinum credit card...
Change colour to PC Plod's lights to reply.

In article , Mike Bristow
writes
OTOH hand , when was the last time that you heard of trains being stuck or
cancelled because the 3rd rail fell over?
Sometime around last year, around Bank. I can't remember the
details, but I think the central conductor rail "fell over", rather
than the outer one.

I've seen various reports at various times along the lines of "65
positive shoes found just outside X station because of a displaced
current rail". You even get the really nasty case where the displaced
rail displaces a shoe, which then displaces another piece of current
rail elsewhere, which ....

--
Clive D.W. Feather, writing for himself | Home:
Tel: +44 20 8371 1138 (work) | Web: http://www.davros.org
Fax: +44 870 051 9937 | Work:
Written on my laptop; please observe the Reply-To address

Displaced Conductor rails do happen, but not as often as damaged
overhead wires. And it doesn't take as long to repair.

C



On Wed, 13 Aug 2003 07:07:29 +0000 (UTC), Mike Bristow
wrote:

In article ,
Boltar wrote:
OTOH hand , when was the last time that you heard of trains being stuck or
cancelled because the 3rd rail fell over?

Sometime around last year, around Bank. I can't remember the
details, but I think the central conductor rail "fell over", rather
than the outer one.

(OK: so it was trains being stuck/delayed/canceled because the 4th
rail fell over, rather then the 3rd. And it was a rather unusual
incident.)


Life without sex just isn't life.
Make love not war!

Michael Bell wrote in message ...
It has always seemed to me that the 750 volt 3rd rail is a bad
idea. Rather it is the idea that somebody (Sprague?) first thought of
and it got made permanent. Its drawbacks in its present form seem to
me to be :-

* The possibility of electrocuting somebody. Are there many
casualties? More difficult to answer; how much do the procedures to
avoid electrocution cost in direct and indirect costs?

* It too often gets covered with ice in winter (and wet leaves
in autumn?)

So does the Overhead Line.......

* The danger of electrocution means that voltages cannot be
raised to increase power delivery. Italian state railways (FS =
Ferrovia della Stato) started with 3000 volt overhead wires, but
everything has now been done so that they can increase the voltage to
6000 volts, so doubling the power that can be delivered.


Well how many people do you know that get up in the morning and take
the dog for a walk down the third rail? I know some idiots do it but
the majority don't!

So I have been thinking of the possibilities of shielding the
3rd rail. The shield would be made of springy plastic, with square
holes moulded in the bottom, to allow rainwater and leaves to drop out
of the bottom and cooling air to rise through them. The holes would be
too small to allow a hand to be put through and too far for a finger
to reach the 3rd rail.

And whos going to pay for this?

To be honest I'm supprised your not complaining at overhead
powerlines, street cables etc. Someone could easily kill themselves by
sticking a knitting needle into a plug socket and turning it on, and
many places have high voltage sockets for cleaning equipment. Are you
one of these doughnuts who is trying to dieselise the country?

On Fri, 8 Aug 2003 23:43:59 +0100, Michael Bell

wrote in :

* The danger of electrocution means that voltages cannot be
raised to increase power delivery. Italian state railways (FS =
Ferrovia della Stato) started with 3000 volt overhead wires, but
everything has now been done so that they can increase the voltage to
6000 volts, so doubling the power that can be delivered.

Redo your maths; V*2 = P*4, modulo foibles of inductive loads.

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. Room 40-1-B12, CERN
KotPT -- "for stupidity above and beyond the call of duty".