On Mon, 8 Oct 2007, Paul Scott wrote:

"Abigail Brady" wrote in message
ups.com...

I was pondering a map the other day, and I noted quite how close
Moorgate and Cannon Street are. I guess the city widened lines to
Moorgate are a lost cause due to the planned work at Farringdon, but I
wondered whether it has ever been suggested to extend the Northern City
Line south of Moorgate and link up with the line at Cannon Street,
making Cannon Street into a through station.

Has this ever been suggested?

Yes, about every eighteen months on this group!

Are they any especial difficulties apart from the sheer cost of
tunnelling in EC2. (Bank of England vaults?, I can also imagine the
gradient being a problem)?

Gradient would definitely be an issue

Cannon Street bridge is 7.1 metres above the high water level of the
Thames [1], perhaps less at the ends. The rail deck will be a little above
that - not more than 9 metres, and probably less. It's about 260 metres
from the point where the bridge makes landfall to Cannon Street itself,
where the space occupied by the station ends (ish). If you hollowed out
the existing station and put in a downward-sloping track at a gradient of
1:30 (generally considered the practical maximum, i think), you could drop
8.5 metres in that distance, leaving you at about the level of the river.
You need about four metres over the top of the track for the train (six if
you want OHLE, which we don't). If Cannon Street is four metres or more
above the level of the river, this idea is just about plausible - at least
this far!

In terms of getting to Moorgate, you're then alright, as you have about
650 metres to run, in which space you can dive another 20 metres, which i
think is enough. The problem, of course, is all the buildings and whatnot
in between the two. If you could run under Walbrook and Prince's St,
though, you might be alright. You might need to demolish No 1 Poultry, but
it's a horrible building anyway.

Don't ask me about how it all fits in with the Bank station complex.
Didn't someone say they thought that was plausible?

Lonelytraveller mentioned the Walbrook; i don't know what you'd do about
that either.

When DLR extensions have been suggested in the past it is usually
mentioned that the Bank of England vaults are in the way too!

The vaults thing is a red herring when it comes to the NCL, though - there
have been serious proposals from the time it opened up to the 1960s to
extend it southward, and none of those had any problem with vaults.

The alternative to going to Cannon Street is to stay in deep tunnel, cross
the river, go to underground platforms at London Bridge, and then surface
onto the appropriate tracks east of the station, bypassing Cannon Street
and its spur altogether. Although if you're going to do this, you might as
well take the tunnel west and do something more interesting ...

tom

[1] http://www.the-river-thames.co.uk/bridgeheights.htm

--
Hawaii may be many things, but it is not the sort of place you go to
for smart, sexy, geeky women. It's more the place for luau excess,
non-literate arts, and maritime athleticism. -- applez

Tom Anderson wrote:

Cannon Street bridge is 7.1 metres above the high water level of the
Thames [1], perhaps less at the ends. The rail deck will be a little
above that - not more than 9 metres, and probably less. It's about
260 metres from the point where the bridge makes landfall to Cannon
Street itself, where the space occupied by the station ends (ish). If
you hollowed out the existing station and put in a downward-sloping
track at a gradient of 1:30 (generally considered the practical
maximum, i think), you could drop 8.5 metres in that distance, leaving you
at about the level of the
river. You need about four metres over the top of the track for the
train (six if you want OHLE, which we don't). If Cannon Street is
four metres or more above the level of the river, this idea is just
about plausible - at least this far!

In terms of getting to Moorgate, you're then alright, as you have
about 650 metres to run, in which space you can dive another 20
metres, which i think is enough.

You would need to have flat platforms under Walbrook, to replace Cannon
Street Station.

You would need to have flat platforms under Walbrook, to replace Cannon
Street Station.
But if you did that, you'd have to avoid the Walbrook river on top of
you, as well as building foundations either side - you'd make it quite
awkward for the platform exits..

On Tue, 9 Oct 2007, John Rowland wrote:

Tom Anderson wrote:

Cannon Street bridge is 7.1 metres above the high water level of the
Thames [1], perhaps less at the ends. The rail deck will be a little
above that - not more than 9 metres, and probably less. It's about 260
metres from the point where the bridge makes landfall to Cannon Street
itself, where the space occupied by the station ends (ish). If you
hollowed out the existing station and put in a downward-sloping track
at a gradient of 1:30 (generally considered the practical maximum, i
think), you could drop 8.5 metres in that distance, leaving you at
about the level of the river. You need about four metres over the top
of the track for the train (six if you want OHLE, which we don't). If
Cannon Street is four metres or more above the level of the river, this
idea is just about plausible - at least this far!

In terms of getting to Moorgate, you're then alright, as you have about
650 metres to run, in which space you can dive another 20 metres, which
i think is enough.

You would need to have flat platforms under Walbrook, to replace Cannon
Street Station.

Either there or further north. If the station was part of the Bank
complex, you might need to add another exit somewhere.

tom

--
It is a laborious madness, and an impoverishing one, the madness of
composing vast books. -- Jorge Luis Borges

If you hollowed out
the existing station and put in a downward-sloping track at a gradient of
1:30 (generally considered the practical maximum, i think), you could drop
But if you did that, you wouldn't have Cannon Street Station, meaning
that the Commuters all pile off the trains at whatever the next
station is - presumably Bank, which would be a disaster in terms of
how busy that station is already.

You might need to demolish No 1 Poultry, but it's a horrible building anyway.
Its not such a problem - the bottom 2 floors worth of basement are
isolated from the rest of the building with a concrete slab in between
- they did that so that archaeologists could get down there while they
were building the building above them. But, if you were heading in
that direction, you'd run straight into the Waterloo & City line
platforms, travelator, or the passenger tunnel between the Waterloo &
City platforms and the Central Line.

Don't ask me about how it all fits in with the Bank station complex.
Didn't someone say they thought that was plausible?
It's only really possible if you rebuild the waterloo and city line
platform entrances so that they take a different route; the travelator
and the interchange tunnel effectively block the through-route - the
only way to avoid this is to go below this level, but then you would
need a very steep slope indeed. You can't get through on the right
hand side of the northern line either, because that's where the
Central line platforms and escalator are.

When DLR extensions have been suggested in the past it is usually
mentioned that the Bank of England vaults are in the way too!
The vaults thing is a red herring when it comes to the NCL, though - there
have been serious proposals from the time it opened up to the 1960s to
extend it southward, and none of those had any problem with vaults.
(from the north) I'd assume it would be fine until you actually reach
Bank station - at that point, if you turn right, you hit the (former)
Midland Bank HQ (now some other bank's important building) vaults,
unless you make it a 45 degree turn. The alternative is to pass
through the slight gap between the central line and the ticket hall,
over the northern line, and then turn right. You can't really head
straight on, because there are loads of vaults around there. The DLR
platforms are to the west of the Northern line ones, rather than
directly below, presumably to help avoid undermining them, or the
buildings above - anything any higher would thus need to be to the
east, which basically means you end up heading more towards Monument,
not Cannon street, and there are quite a few listed churches in that
direction, as well as office vaults, that you wouldn't want to
interfere with.

On Tue, 9 Oct 2007, lonelytraveller wrote:

If you hollowed out the existing station and put in a downward-sloping
track at a gradient of 1:30 (generally considered the practical
maximum, i think), you could drop

But if you did that, you wouldn't have Cannon Street Station, meaning
that the Commuters all pile off the trains at whatever the next station
is - presumably Bank, which would be a disaster in terms of how busy
that station is already.

You'd add more exits and passageways when you added the platforms.

You might need to demolish No 1 Poultry, but it's a horrible building anyway.

Its not such a problem - the bottom 2 floors worth of basement are
isolated from the rest of the building with a concrete slab in between -
they did that so that archaeologists could get down there while they
were building the building above them.

Ah, interesting.

But, if you were heading in that direction, you'd run straight into the
Waterloo & City line platforms, travelator, or the passenger tunnel
between the Waterloo & City platforms and the Central Line.

Yes, you'd have to get deep enough to pass under those. Getting past the
District line is going to be interesting too.

When DLR extensions have been suggested in the past it is usually
mentioned that the Bank of England vaults are in the way too!

The vaults thing is a red herring when it comes to the NCL, though -
there have been serious proposals from the time it opened up to the
1960s to extend it southward, and none of those had any problem with
vaults.

(from the north) I'd assume it would be fine until you actually reach
Bank station - at that point, if you turn right, you hit the (former)
Midland Bank HQ (now some other bank's important building) vaults,
unless you make it a 45 degree turn. The alternative is to pass through
the slight gap between the central line and the ticket hall, over the
northern line, and then turn right. You can't really head straight on,
because there are loads of vaults around there. The DLR platforms are to
the west of the Northern line ones, rather than directly below,
presumably to help avoid undermining them, or the buildings above -
anything any higher would thus need to be to the east, which basically
means you end up heading more towards Monument, not Cannon street, and
there are quite a few listed churches in that direction, as well as
office vaults, that you wouldn't want to interfere with.

I believe the plan for extensions of the line beyond Bank has always been
to make it really deep, so it's below any of this stuff.

tom

--
It is a laborious madness, and an impoverishing one, the madness of
composing vast books. -- Jorge Luis Borges

On 10 Oct, 06:10, Tom Anderson wrote:
I believe the plan for extensions of the line beyond Bank has always been
to make it really deep, so it's below any of this stuff.
And how does it get below the northern line in the short distance to
travel, when it starts by being above it, without it having to invade
bank vaults on either side?

On Wed, 10 Oct 2007, lonelytraveller wrote:

On 10 Oct, 06:10, Tom Anderson wrote:

I believe the plan for extensions of the line beyond Bank has always been
to make it really deep, so it's below any of this stuff.

And how does it get below the northern line in the short distance to
travel, when it starts by being above it, without it having to invade
bank vaults on either side?

Not a clue. But that's what the plans were!

tom

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