In article ,
() wrote:

On Tue, 8 Aug 2017 17:47:29 +0100, Basil Jet
wrote:

On 2017\08\08 11:54, Recliner wrote:

That's true of most Tube tunnel portals, as the initial shallow
section is cut and cover. The TBMs only do the deep tunneling.

I've just looked at numerous tube portals in Bing Maps using the 45
degree view. The pair of round portals are clearly visible in most. I
have found none which clearly match your description.

The Picaddilly tunnel where it goes down after Barons Court is just
visible on those maps and isn't round portals.

Only because there's a (fairly short) covered way before the tunnels start.

--
Colin Rosenstiel

wrote:
In article ,
() wrote:

On Tue, 8 Aug 2017 17:47:29 +0100, Basil Jet
wrote:

On 2017\08\08 11:54, Recliner wrote:

That's true of most Tube tunnel portals, as the initial shallow
section is cut and cover. The TBMs only do the deep tunneling.

I've just looked at numerous tube portals in Bing Maps using the 45
degree view. The pair of round portals are clearly visible in most. I
have found none which clearly match your description.

The Picaddilly tunnel where it goes down after Barons Court is just
visible on those maps and isn't round portals.

Only because there's a (fairly short) covered way before the tunnels start.

Of course, but that was exactly my point (read the thread): many of the
tube tunnel portals have a short, double-track, cut and cover section
before the separate circular deep tubes start. As a result, the latter
aren't visible from outside.

On 2017\08\08 22:02, Recliner wrote:
Basil Jet wrote:
On 2017\08\08 11:54, Recliner wrote:

That's true of most Tube tunnel portals, as the initial shallow
section is cut and cover. The TBMs only do the deep tunneling.

I've just looked at numerous tube portals in Bing Maps using the 45
degree view. The pair of round portals are clearly visible in most. I
have found none which clearly match your description.

I don't think the round Tube tunnels are visible at either end of the
Jubilee line,

Finchley Road - N/A shared with Met.
Canning Town - the lines are covered by a structure which I believe has
something to do with flood protection.

nor the Bakerloo line,

N/A straddling DC line

nor the western end of the Piccadilly line;

N/A shared with District

not sure of the eastern end,

Bounds Green, Southgate South and Southgate North all have twin portals
visible from the air. Southgate North is very visible from a footbridge
(IRL, not on the internet) which enables you to easily see that the
entrance is larger than the exit for air pressure reasons.

but I don't think so. The Central line
Stratford tunnel portals are separate, with Crossrail tracks in between,
while the (separate) western portals are buried under the Westfield
development and no longer visible. I'm not sure about the Northern line
northern portals,

Finchley - N/A because of depot access between passenger tracks
Golders Green - 3 tubes visible (sic)
Hendon Central - 2 tubes visible
Colindale - can't tell, but almost certainly has separate tubes visible
in the right light

but the tube tunnels are visible at Morden.

Visible from the platforms IIRC.

The Victoria line and Drain are entirely underground, so no portals. The
DLR Bank tunnel round tube tunnels are visible, but I don't think the other
DLR tube tunnels are.

On 2017\08\09 03:18, wrote:
On Wed, 9 Aug 2017 02:22:46 +0100, Basil Jet
wrote:


nor the western end of the Piccadilly line;

N/A shared with District
Where do District trains share a tunnel entrance with the Piccadilly ?

You're right, they don't... the Picc trains descend between the District
tracks west of West Kensington. I can't be sure from Bing what the
portal looks like.


visible from the air. Southgate North is very visible from a footbridge
(IRL, not on the internet) which enables you to easily see that the
entrance is larger than the exit for air pressure reasons.

Is that this location
http://www.geograph.org.uk/photo/1400129

Yes

The exit northbound is two different sizes in quick succession
http://www.geograph.org.uk/photo/1400129

I think the outer one is to create an impression of symmetry with the
entrance, which is the same size but extends inward with the larger
diameter. I'm not sure why symmetry would be important in a portal pair
though.

In message
-septe
mber.org, at 21:02:55 on Tue, 8 Aug 2017, Recliner
remarked:

The Victoria line

Must make getting the trains in and out of the depot at Northumberland
Park a bitch.

and Drain

Up to a point. The depot at Waterloo (which I've had a walking tour
round back in the day) is more sunken than under*ground*.

https://c1.staticflickr.com/6/5067/5...83047678_b.jpg

are entirely underground, so no portals.

https://binged.it/2frzpgA
--
Roland Perry

wrote:
On Wed, 9 Aug 2017 02:22:46 +0100, Basil Jet
wrote:


nor the western end of the Piccadilly line;

N/A shared with District
Where do District trains share a tunnel entrance with the Piccadilly ?
AFAIK they only share tracks occasionally between Hammersmith and
Acton town and the odd District non passenger working to Northfields.

The District and Picc lines share track from Acton Town through Ealing
Common station to Hanger Lane Junction. Once in a while, a District line
train gets sent, wrongly, towards North Ealing, and occasionally Piccadilly
line trains serve Ealing Broadway.

Years ago it used be a District route shared with the Piccadilly but
that stopped long before the line was extended to Heathrow

Originally it was purely a District line route all the way to Hounslow. The
Piccadilly line came later.

In message , at 07:44:52 on Thu, 3 Aug
2017, Roland Perry remarked:

2. Bedford to Kettering. Newly electrified,

Is it, already?

Not completed, but intended to be.

We are talking about NR and Grayling here. The only thing you can
reasonably expect is that whatever they claim today may change tomorrow.

suitable for 125 mph electric
or diesel trains. IEPs will outperform the existing diesels.

3. Kettering to Leicester and on to Derby, Nottingham and Sheffield.
Electrification work started,

Just a few bridge works.

but work will be suspended indefinitely. Bi-mode IEPs will be able to
run, but performance will be worse than current diesel trains,
specially the Meridians.

So keep the Meridians.

Yes, but not the HSTs.

There's only one tph (to Nottingham) operated by HSTs, and now
electrification has been cancelled they'll have to find something else
to replace the HST. But I doubt it'll be IEPs.

It occurs to me that if the line is electrified to Corby (despite it
being "North of Kettering", that's what the "Bedford to Kettering
electrification" is all about) then they could release the three
Meridians used for that service to replace HSTs on the main line.

--
Roland Perry

On Wed, 09 Aug 2017 09:41:23 +0100
wrote:
As a child I liked going to Hounslow West as walking along the pathway
behind the buffers gave you an unusual view of the trains, it aslo
meant we were visiing Heathrow either to watch planes from the viewing
area or visit the hangers where a relative had access.

I think the only sub surface train I have travelled on the route was
the Steam special from Northfields a couple of years back.

How far can a sub surface stock go down the heathrow branch these days?
Obviously the heathrow tunnels and houslow west are too small for one.

--
Spud

In article , (Basil Jet)
wrote:

On 2017\08\09 03:18, wrote:

The exit northbound is two different sizes in quick succession
http://www.geograph.org.uk/photo/1400129

I think the outer one is to create an impression of symmetry with the
entrance, which is the same size but extends inward with the larger
diameter. I'm not sure why symmetry would be important in a portal
pair though.

Aesthetics. London Transport was very keen on them in the 1930s, thanks to
Frank Pick.

--
Colin Rosenstiel

In article ,
() wrote:

On Tue, 08 Aug 2017 19:42:39 -0500,
wrote:

In article ,
() wrote:

On Tue, 8 Aug 2017 17:47:29 +0100, Basil Jet
wrote:

On 2017\08\08 11:54, Recliner wrote:

That's true of most Tube tunnel portals, as the initial shallow
section is cut and cover. The TBMs only do the deep tunneling.

I've just looked at numerous tube portals in Bing Maps using the 45
degree view. The pair of round portals are clearly visible in most. I
have found none which clearly match your description.

The Picaddilly tunnel where it goes down after Barons Court is just
visible on those maps and isn't round portals.

Only because there's a (fairly short) covered way before the tunnels
start.

So there is a short section on the approach to the tunnels from the
surface that was dug and covered . Seems to match what Recliner
described fairly accurately. Are you saying that section just because
it is short does not count as Cut and Cover.

In the case of the Piccadilly line portal east of Baron's Court it's all
part of the structure of the cutting from which the tunnels start. It's even
possible that part of the covered way was added later when the tracks
between West Kensington and Hammersmith were rearranged when the Piccadilly
was projected westwards in the 1930s.

--
Colin Rosenstiel