On Sun, 20 Apr 2008, Richard J. wrote:

Mwmbwls wrote:

Preliminary Airtrack plans - designed to provide new rail access to
Heathrow from the south and west - were discussed at the meeting of
Spelthorne Council's executive committee on Tuesday. It voted to
strongly oppose overhead electrification on environmental grounds.

That's rich, coming from the council that did a U-turn and voted in
favour of Heathrow expansion. They don't mind destroying someone else's
village and forcing environmental damage on thousands of West London
residents, but they don't want the view of their sodding bit of grass
spoilt.

Aha - 'sodding grass'. Very good.

tom

--
Initial thoughts - who cares? Subsequent thoughts - omg!!! (Female, 14,
Scotland) -- 4.5 million young Brits' futures could be compromised by
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In uk.railway Mwmbwls wrote:
Spelthorne Councillors seek to choose Airtrack electrification
voltage. It reminds me of the days when London had conduit trams
because overhead wires were considered unsightly - but then at least
they owned the streets and the trams - unlike Spelthorne. This is
surely a technical rather than a political question. Note also Mr
Livingstone's response.

Airtrack's going to have to have a voltage changeover point somewhere. The
council have suggested it should be at T5 for environmental reasons. I
don't see a problem with them saying that, if it is just a proposal. There
may well be technical, operational or other reasons which means third rail
is impractical or costly on that stretch but that's for the developers to
make a case for.

The council have stated their opinion. Often planning ends up being
something of a compromise; you have to start from some negotiating positions
so you can then move towards that compromise. The negotiating positions are
by definition more extreme (at both sides) than the compromise.

Theo

"Theo Markettos" wrote

Airtrack's going to have to have a voltage changeover point somewhere.
The
council have suggested it should be at T5 for environmental reasons. I
don't see a problem with them saying that, if it is just a proposal.
There
may well be technical, operational or other reasons which means third rail
is impractical or costly on that stretch but that's for the developers to
make a case for.

Airtrack, as currently planned, will terminate at T5. It has been stated
that the tunnel approach to the station, and the Airtrack platforms at T5
will have to be 25kV OHLE, though I haven't seen an explanation of why this
is so. This being the case, there will have to be a voltage change somewhere
between Staines and T5. It would seem to make sense, in the longer term, for
Airtrack and Heathrow Express and/or Crossrail to link up, with through
running, which of course would require dual-voltage stock and a voltage
change somewhere. An intermediate possibility is for HEx to be extended to
Staines.

Peter

Peter Masson wrote:
Airtrack, as currently planned, will terminate at T5. It has been stated
that the tunnel approach to the station, and the Airtrack platforms at T5
will have to be 25kV OHLE, though I haven't seen an explanation of why this
is so.

I wondered about corrosion of rails etc in the tunnels?

This being the case, there will have to be a voltage change somewhere
between Staines and T5. It would seem to make sense, in the longer term, for
Airtrack and Heathrow Express and/or Crossrail to link up, with through
running, which of course would require dual-voltage stock and a voltage
change somewhere. An intermediate possibility is for HEx to be extended to
Staines.

So that starts to make the case for a change at Staines...

Theo

On Sun, 20 Apr 2008, Peter Masson wrote:

"Theo Markettos" wrote

Airtrack's going to have to have a voltage changeover point somewhere.
The council have suggested it should be at T5 for environmental
reasons. I don't see a problem with them saying that, if it is just a
proposal. There may well be technical, operational or other reasons
which means third rail is impractical or costly on that stretch but
that's for the developers to make a case for.

Airtrack, as currently planned, will terminate at T5.

Yes. Which means there's no reason for any OHLE at all.

It has been stated that the tunnel approach to the station, and the
Airtrack platforms at T5 will have to be 25kV OHLE, though I haven't
seen an explanation of why this is so.

Which would be nice to see, because that sounds like a totally bonkers
idea.

This being the case, there will have to be a voltage change somewhere
between Staines and T5. It would seem to make sense, in the longer term,
for Airtrack and Heathrow Express and/or Crossrail to link up, with
through running, which of course would require dual-voltage stock and a
voltage change somewhere.

In which case, since the stock will have to be dual-voltage anyway, why
bother making the Airtrack bit OHLE? Why not have the change at T5, thus
allowing third-rail trains to run from the south into T5 too?

An intermediate possibility is for HEx to be extended to Staines.

This is the only reason i can think of for doing it. Even then, it means
sacrificing the ability to run third-rail stock into T5 for this mythical
future option. Is it the case that existing stock won't be allowed anyway,
for safety or ABB [1] reasons?

tom

[1] Arbitrary BAA bull****

--
Initial thoughts - who cares? Subsequent thoughts - omg!!! (Female, 14,
Scotland) -- 4.5 million young Brits' futures could be compromised by
their electronic footprint, Information Commissioner's Office

"Tom Anderson" wrote in message
h.li...

An intermediate possibility is for HEx to be extended to Staines.

This is the only reason i can think of for doing it. Even then, it means
sacrificing the ability to run third-rail stock into T5 for this mythical
future option.

As the consultation report points out though, the two dedicated Airtrack
platforms under T5 are a terminus from the west, it is only the HEx
platforms that can be turned into through platforms, joining Airtrack
somewhere to the west of the station. So even extensions to HEx might'nt
necessarily affect terminating DC trains if the changeover was in the
vicinity of the station.

Is it the case that existing stock won't be allowed anyway, for safety or
ABB [1] reasons?

If existing stock such as 450s was used by SWT - except for having shoes
rather than pantograph it is to all intents identical to the Heathrow
Connect 360s [ref other discussions about AC traction in all modern EMUs],
with the end gangways being an additional safety feature, [although not
required in the Heathrow tunnels as they have walkways].

I also don't believe there are any increased safety issues with underground
third rail stations, if there was such a huge issue why would they be
carrying on with a new third rail installation for the ELL? Another poster
has mentioned corrosion in the tunnels, but this is surely overcome with
modern slab track and fastenings in concrete linings - they don't suffer
from groundwater ingress like the early LU tunnels...

Paul S