On Nov 24, 11:11*pm, D7666 wrote:
On Nov 24, 10:50 pm, (Neil Williams)
wrote

DOO mirrors are certainly fitted at all the stations on that route.

Watford / Snorbens has got mirrors but the 321 is crewed.

I'm probably wrong but I thought mirrors are an aid to driver to see
guard but DOO needs CCTV ?

The WAGN services through New Barnet and Oakleigh Park down to
Moorgate and Kings Cross used to have CCTV, but it was removed and
replaced with mirrors. I don't know what the significance of that
was.

ian

On Thu, 27 Nov 2008 15:05:11 -0800 (PST),
wrote:

On Nov 24, 11:11*pm, D7666 wrote:
On Nov 24, 10:50 pm, (Neil Williams)
wrote

DOO mirrors are certainly fitted at all the stations on that route.

Watford / Snorbens has got mirrors but the 321 is crewed.

I'm probably wrong but I thought mirrors are an aid to driver to see
guard but DOO needs CCTV ?

The WAGN services through New Barnet and Oakleigh Park down to
Moorgate and Kings Cross used to have CCTV, but it was removed and
replaced with mirrors. I don't know what the significance of that
was.

"KISS"
IMU despite the efforts of vandals the mirrors were more "reliable".

On Nov 28, 5:23*am, Charles Ellson wrote:

IMU despite the efforts of vandals the mirrors were more "reliable".

In that case do take a run along Watford Snorbens.

Snorbens Abbey mirror is completely wrecked, and has been so for a
very long time, and one of the others is almost as bad, forget which
one.

--
Nick

"Charles Ellson" wrote in message
...
On Mon, 24 Nov 2008 20:32:20 -0000, wrote:

Is a fourth rail really necessary out that way, however?

It is if you want the same train to work both there and on the
Underground.

Was the 38 stock on Island Line modified to work only on third rail? What
did that require, if that was the case?

I always understood
that they were really needed only for the tub sections of the tube, to
help
power flow into the motors.

No the LU 4-rail power supply is intended to keep the traction current
within the two conductor rails and not find its way back via other
bits of metal with consequent damage.

In case of flooding, perhaps?

I heard this on the Island Line, where 38 stock operates only with a 3rd
rail.

No tube tunnels or aforementioned metalwork to worry about.

Then what is the problem with Bakerloo line trains continuing further north,
assuming that they don't require any modifications?

"Neil Williams" wrote in message
...
On 25 Nov, 14:05, "Richard J." wrote:

Might it be easier to fit CCTV to the train rather than the platform?
I think some of the Electrostars have this facility?

Southern trains have this.

On Sat, 29 Nov 2008 14:06:54 -0000, wrote:

"Charles Ellson" wrote in message
.. .
On Mon, 24 Nov 2008 20:32:20 -0000, wrote:

Is a fourth rail really necessary out that way, however?

It is if you want the same train to work both there and on the
Underground.

Was the 38 stock on Island Line modified to work only on third rail? What
did that require, if that was the case?

I always understood
that they were really needed only for the tub sections of the tube, to
help
power flow into the motors.

No the LU 4-rail power supply is intended to keep the traction current
within the two conductor rails and not find its way back via other
bits of metal with consequent damage.

In case of flooding, perhaps?

No. Current leaking to ground and causing electrolytic corrosion.

Remember, there were already pipes etc under London before the tubes
were built, and the tubes were lined with cast iron segments..

Tram and streetcar track had the running rails at minus 10 volts so
that stray current leaked from ground to the rails instead of vice
versa.

LU's centre rail is I believe at minus 200 volts.

This is a major problem for the elevated sections of the New York
Subway, which is 600v 3-rail running on continuous girder bridge. I
saw some TV footage of the electrolyic corrosion damage recently.

I heard this on the Island Line, where 38 stock operates only with a 3rd
rail.

No tube tunnels or aforementioned metalwork to worry about.

Then what is the problem with Bakerloo line trains continuing further north,
assuming that they don't require any modifications?

They would need them - and would probably be prohibited from the
underground section.

On Nov 29, 2:52*pm, Christopher A. Lee wrote:
On Sat, 29 Nov 2008 14:06:54 -0000, wrote:
"Charles Ellson" wrote in message
.. .
On Mon, 24 Nov 2008 20:32:20 -0000, wrote:

Is a fourth rail really necessary out that way, however?

It is if you want the same train to work both there and on the
Underground.

Was the 38 stock on Island Line modified to work only on third rail? What
did that require, if that was the case?

I always understood
that they were really needed only for the tub sections of the tube, to
help
power flow into the motors.

No the LU 4-rail power supply is intended to keep the traction current
within the two conductor rails and not find its way back via other
bits of metal with consequent damage.

In case of flooding, perhaps?

No. Current leaking to ground and causing electrolytic corrosion.

Remember, there were already pipes etc under London before the tubes
were built, and the tubes were lined with cast iron segments..

Tram and streetcar track had the running rails at minus 10 volts so
that stray current leaked from ground to the rails instead of vice
versa.

LU's centre rail is I believe at minus 200 volts.

That's interesting, because I was under the impression that there was
no danger from the middle track, but 200 V could presumably give a
whack if there was any current.

In message , Christopher A.
Lee writes
No. Current leaking to ground and causing electrolytic corrosion.

Remember, there were already pipes etc under London before the tubes
were built, and the tubes were lined with cast iron segments..

Tram and streetcar track had the running rails at minus 10 volts so
that stray current leaked from ground to the rails instead of vice
versa.

LU's centre rail is I believe at minus 200 volts.

Traction current is fed at +420v (positive) on the outside rails and
-210v on the centre rail (negative) the sum of these giving a traction
feed of 630v dc.

They are 'loosely' tied to earth through resistances in the sub stations
that feed the supply. Despite being an electrician in a previous life
and now a driver, I struggle to get my head round 'loosely tied to
earth' and what it means in real life.

I recollect an incident a few years ago when the traction current had
been discharged (turned off) due to person under a train. For
complicated reasons, the centre rail had become live at +420v. The
paramedic who was working under the train and touched that rail and
earth looked extremely pale afterwards. It was described to me like
having your hand hit by a sledgehammer.
--
Steve Fitzgerald has now left the building.
You will find him in London's Docklands, E16, UK
(please use the reply to address for email)

On Sat, 29 Nov 2008 09:26:38 -0800 (PST), MIG
wrote:

On Nov 29, 2:52*pm, Christopher A. Lee wrote:
On Sat, 29 Nov 2008 14:06:54 -0000, wrote:
"Charles Ellson" wrote in message
.. .
On Mon, 24 Nov 2008 20:32:20 -0000, wrote:

Is a fourth rail really necessary out that way, however?

It is if you want the same train to work both there and on the
Underground.

Was the 38 stock on Island Line modified to work only on third rail? What
did that require, if that was the case?

I always understood
that they were really needed only for the tub sections of the tube, to
help
power flow into the motors.

No the LU 4-rail power supply is intended to keep the traction current
within the two conductor rails and not find its way back via other
bits of metal with consequent damage.

In case of flooding, perhaps?

No. Current leaking to ground and causing electrolytic corrosion.

Remember, there were already pipes etc under London before the tubes
were built, and the tubes were lined with cast iron segments..

Tram and streetcar track had the running rails at minus 10 volts so
that stray current leaked from ground to the rails instead of vice
versa.

LU's centre rail is I believe at minus 200 volts.

That's interesting, because I was under the impression that there was
no danger from the middle track, but 200 V could presumably give a
whack if there was any current.

There isn't much current if there's nothing in section. You used to
see track workers hopping on and off the centre rail and walking along
it.

"MIG" wrote in message
...

: That's interesting, because I was under the impression that there was
: no danger from the middle track, but 200 V could presumably give a
: whack if there was any current.

Doesn't the live rai change back and forth between third and fourth
position? I remember hearing that the live rail is always in the third
position when in a station, because there is less of a risk of somebody
getting fried, should they fall onto the tracks. But the positive can be in
fourth position just before and after the station.