On Dec 2, 3:39*pm, Tom Anderson wrote:
My gut feeling is that adding a third bore to a two-bore setup is a lot
more expensive than adding a footbridge to a railway bridge. In fact, i
can't see how there being two bores there already makes the third any
cheaper, so it would be as expensive as building it as a standalone.

The DLR Woolwich Arsenal twin tunnels were built by sending one boring
machine from King George V to Woolwich, turning it round, and sending
it back again. So in theory you could give it another twirl (probably
works OK time-wise too, as fitting out a rail tunnel takes a lot
longer than fitting out a foot/cycle tunnel) for at least *some* cost
savings.

--
John Band
john at johnband dot org
www.johnband.org

On Tue, 2 Dec 2008, John B wrote:

On Dec 2, 3:39*pm, Tom Anderson wrote:
My gut feeling is that adding a third bore to a two-bore setup is a lot
more expensive than adding a footbridge to a railway bridge. In fact, i
can't see how there being two bores there already makes the third any
cheaper, so it would be as expensive as building it as a standalone.

The DLR Woolwich Arsenal twin tunnels were built by sending one boring
machine from King George V to Woolwich, turning it round, and sending it
back again. So in theory you could give it another twirl (probably works
OK time-wise too, as fitting out a rail tunnel takes a lot longer than
fitting out a foot/cycle tunnel) for at least *some* cost savings.

Yebbut then you've got to pack it up at the far end, rather than at the
near end, where it started, and where you thus already have all the gear
and access. Logically, you should bore a *fourth* tunnel, to minimise
costs.

tom

--
I could tell you a great many more particulars but suppose that you are
tired of it by this time. -- John Backhouse, Trainspotter Zero

"Tom Anderson" wrote in message
h.li...
On Tue, 2 Dec 2008, John B wrote:

On Dec 2, 3:39 pm, Tom Anderson wrote:
My gut feeling is that adding a third bore to a two-bore setup is a lot
more expensive than adding a footbridge to a railway bridge. In fact, i
can't see how there being two bores there already makes the third any
cheaper, so it would be as expensive as building it as a standalone.

The DLR Woolwich Arsenal twin tunnels were built by sending one boring
machine from King George V to Woolwich, turning it round, and sending it
back again. So in theory you could give it another twirl (probably works
OK time-wise too, as fitting out a rail tunnel takes a lot longer than
fitting out a foot/cycle tunnel) for at least *some* cost savings.

Yebbut then you've got to pack it up at the far end, rather than at the
near end, where it started, and where you thus already have all the gear
and access. Logically, you should bore a *fourth* tunnel, to minimise
costs.


You'd have to bore a fourth tunnel, to separate the cyclists and the
pedestrians.

c.f. the various Tyne tunnels, where they are just completing the fourth
(sunken prefabricated) tunnel, having done everything in the wrong order
over the years... :-)

Paul S

On Tue, 2 Dec 2008, Paul Scott wrote:

"Tom Anderson" wrote in message
h.li...
On Tue, 2 Dec 2008, John B wrote:

On Dec 2, 3:39 pm, Tom Anderson wrote:
My gut feeling is that adding a third bore to a two-bore setup is a lot
more expensive than adding a footbridge to a railway bridge. In fact, i
can't see how there being two bores there already makes the third any
cheaper, so it would be as expensive as building it as a standalone.

The DLR Woolwich Arsenal twin tunnels were built by sending one boring
machine from King George V to Woolwich, turning it round, and sending it
back again. So in theory you could give it another twirl (probably works
OK time-wise too, as fitting out a rail tunnel takes a lot longer than
fitting out a foot/cycle tunnel) for at least *some* cost savings.

Yebbut then you've got to pack it up at the far end, rather than at the
near end, where it started, and where you thus already have all the gear
and access. Logically, you should bore a *fourth* tunnel, to minimise
costs.

You'd have to bore a fourth tunnel, to separate the cyclists and the
pedestrians.

No, you need a cycle tunnel in each direction. Rubber rings for
pedestrians.

tom

--
I could tell you a great many more particulars but suppose that you are
tired of it by this time. -- John Backhouse, Trainspotter Zero

Tom Anderson wrote:
On Tue, 2 Dec 2008, John Rowland wrote:

How about a hand-wound transporter bridge hanging from the fixed bar
of the flood barrier?

APPROVED. Possibly even pedal-powered!

I want one on Dartford Creek too.

There seems to be no fixed bar in the flood barrier there, so it would be
more expensive. And I don't think there are any ships there either, making
it a bit pointless. I don't think a hand-wound chain ferry like the one on
Trowbridge Island, Kingston would work well on a tidal creek. So a standard
bridge would probably be cheaper.

John Rowland wrote:
Tom Anderson wrote:
On Tue, 2 Dec 2008, John Rowland wrote:
How about a hand-wound transporter bridge hanging from the fixed bar
of the flood barrier?
APPROVED. Possibly even pedal-powered!

I want one on Dartford Creek too.

There seems to be no fixed bar in the flood barrier there, so it would be
more expensive. And I don't think there are any ships there either, making
it a bit pointless. I don't think a hand-wound chain ferry like the one on
Trowbridge Island, Kingston would work well on a tidal creek. So a standard
bridge would probably be cheaper.


I've often thought that a simple 'transporter bridge' for foot and bikes
could be built using standard components from a tower crane. With modern
electronics (including secure wireless) the contols and interlocks would
be a piece of cake. You don't need it hand wound as a few small wind
turbines, with a few batteries would easily provide the power and would
give less things for people to fiddle with.

I'd suggested a similar arrangement to cross a 'navigable' river
elsewhere, because approach ramps for a fixed span above navigation
level would require expensive long approach spans (an embankment would
not be permitted as it would obstructe flood flows)

Jim Chisholm

"John Rowland" wrote in message
...
Tom Anderson wrote:
On Tue, 2 Dec 2008, John Rowland wrote:

How about a hand-wound transporter bridge hanging from the fixed bar
of the flood barrier?

APPROVED. Possibly even pedal-powered!

I want one on Dartford Creek too.

There seems to be no fixed bar in the flood barrier there, so it would be
more expensive. And I don't think there are any ships there either, making
it a bit pointless. I don't think a hand-wound chain ferry like the one on
Trowbridge Island, Kingston would work well on a tidal creek. So a
standard bridge would probably be cheaper.

ITYM Trowlock Island, Teddington
--
David Biddulph