Paul Scott wrote:
According to the TL reports, AC/DC changeover stays at Farringdon, its only
DC/AC that moves to City Thameslink. I think so that units that fail to
raise the pan or switch to AC can get into the sidings on third rail. As the
PP suggested, there is already no need for units to stop when dropping the
pan, and most stock can raise the pan on the move as well.
I presume that new trackwork and OHLE will also allow units that fail to
lower the pan/switch to DC to head for the sidings - otherwise what
would be the point of continuing to terminate the 'southbound' OHLE at
Farringdon once the Moorgate branch closes?

David Cantrell wrote:
On Mon, Oct 15, 2007 at 07:30:31PM +0000, Peter Lawrence wrote:

Be thankful for small mervcies. They will have to stop when the AC/DC
changeover point is moved to City TL.!

FFS, if they're going to move it at all, why not move it all the way to
Blackfriars?

Coincidentally, that was actually the original idea (pendantically
speaking the OHLE would also have covered Blackfriars Junction). Judging
by the current plans, units that fail the AC-DC or DC-AC changeover
(at Farringdon and City Thameslink *respectively*) should be able to
retreat to Smithfield Sidings once the new trackwork and OHLE is in
place, although I don't know if the St Paul's Heights guidelines had
influenced Network Rail's decision to cut back on the planned extension
of the OHLE to Blackfriars Junction.

"Sky Rider" wrote in message
...
Paul Scott wrote:
According to the TL reports, AC/DC changeover stays at Farringdon, its
only DC/AC that moves to City Thameslink. I think so that units that fail
to raise the pan or switch to AC can get into the sidings on third rail.
As the PP suggested, there is already no need for units to stop when
dropping the pan, and most stock can raise the pan on the move as well.
I presume that new trackwork and OHLE will also allow units that fail to
lower the pan/switch to DC to head for the sidings - otherwise what would
be the point of continuing to terminate the 'southbound' OHLE at
Farringdon once the Moorgate branch closes?

I don't know the eventual track layout details - does anyone? - but suppose
it has to be looked at in the context of the eventual 24tph service
frequency as well. They'll want to get a southbound failure out of the way
pretty fast, but if there is no provision for a southbound train to get to a
refuge in the sidings, it doesn't really matter where the changeover is
made, so perhaps it might as well just be left where it is. OTOH if there
is to be a crossover to the sidings from the north, then presumably
Farringdon is the best place for an AC/DC failure to be discovered, as you
suggest.

Paul

David Cantrell wrote:
On Mon, Oct 15, 2007 at 07:30:31PM +0000, Peter Lawrence wrote:

Be thankful for small mervcies. They will have to stop when the AC/DC
changeover point is moved to City TL.!

FFS, if they're going to move it at all, why not move it all the way
to Blackfriars?

It would cost more and increase the visual impact of the bridge over the
Thames, for no benefit that I can see.

On 17 Oct, 11:20, "John Rowland"
wrote:
David Cantrell wrote:
On Mon, Oct 15, 2007 at 07:30:31PM +0000, Peter Lawrence wrote:

Be thankful for small mervcies. They will have to stop when the AC/DC
changeover point is moved to City TL.!

FFS, if they're going to move it at all, why not move it all the way
to Blackfriars?

It would cost more and increase the visual impact of the bridge over the
Thames, for no benefit that I can see.

Isn't the bit that goes directly under holborn viaduct very narrow,
height-wise - and not really enough height for overhead lines?

On Tue, 16 Oct 2007 23:22:36 +0100, "Paul Scott"
wrote:


"Sky Rider" wrote in message
...
Paul Scott wrote:
According to the TL reports, AC/DC changeover stays at Farringdon, its
only DC/AC that moves to City Thameslink. I think so that units that fail
to raise the pan or switch to AC can get into the sidings on third rail.
As the PP suggested, there is already no need for units to stop when
dropping the pan, and most stock can raise the pan on the move as well.
I presume that new trackwork and OHLE will also allow units that fail to
lower the pan/switch to DC to head for the sidings - otherwise what would
be the point of continuing to terminate the 'southbound' OHLE at
Farringdon once the Moorgate branch closes?

I don't know the eventual track layout details - does anyone? - but suppose
it has to be looked at in the context of the eventual 24tph service
frequency as well. They'll want to get a southbound failure out of the way
pretty fast, but if there is no provision for a southbound train to get to a
refuge in the sidings, it doesn't really matter where the changeover is
made, so perhaps it might as well just be left where it is. OTOH if there
is to be a crossover to the sidings from the north, then presumably
Farringdon is the best place for an AC/DC failure to be discovered, as you
suggest.

(Partially contradicting what I wrote previously.)

According to the published paper (by Louis G Nel but I have lost the
reference!), the strategy is that southbounds change to DC at
Farringdon but the wires will continue to City TL. In the event of
an AC-DC failure the train will continue on AC to City TL, detrain
passengers and reverse back north (using the existing crossover just
north of Farringdon). Detraining ar Farringdon is impractical due to
the width of the platform.

Northbounds will change over at City TL and will be detrained and
diverted to the sidings in the event of a failure.

I suspect that wiring the sidings may be impractical due to restricted
height.
--
Peter Lawrence

Peter Lawrence wrote:
(Partially contradicting what I wrote previously.)

According to the published paper (by Louis G Nel but I have lost the
reference!), the strategy is that southbounds change to DC at
Farringdon but the wires will continue to City TL.
So the southbound line to City Thameslink will also be wired -
interesting. (By the way, when does the up line from the north become
the down line to the south (and vice-versa)?)
In the event of an AC-DC failure the train will continue on AC to City TL, detrain
passengers and reverse back north (using the existing crossover just
north of Farringdon).
Do you mean the crossover just south of King's Cross Thameslink, or the
crossover between City Thameslink and Smithfield Sidings?
Hypothetically, would 317s be able to use the latter crossover to move
from the southbound line to the northbound line once the OHLE is extended?
Detraining ar Farringdon is impractical due to the width of the platform.
Would this change once Farringdon has been reconstructed in 2011? I
assume this depends on the answer to my second question.
Northbounds will change over at City TL and will be detrained and
diverted to the sidings in the event of a failure.
That certainly ties in with the information regarding the southbound
platform at Farringdon.
I suspect that wiring the sidings may be impractical due to restricted
height.
And there was me looking forward to admiring knitting in the sidings
(not really).

On Thu, 18 Oct 2007 13:24:19 GMT, Sky Rider
wrote:

Peter Lawrence wrote:
(Partially contradicting what I wrote previously.)

According to the published paper (by Louis G Nel but I have lost the
reference!), the strategy is that southbounds change to DC at
Farringdon but the wires will continue to City TL.
So the southbound line to City Thameslink will also be wired -
interesting. (By the way, when does the up line from the north become
the down line to the south (and vice-versa)?)
In the event of an AC-DC failure the train will continue on AC to City TL, detrain
passengers and reverse back north (using the existing crossover just
north of Farringdon).
Do you mean the crossover just south of King's Cross Thameslink, or the
crossover between City Thameslink and Smithfield Sidings?

The latter; I meant south of Farringdon!

Hypothetically, would 317s be able to use the latter crossover to move
from the southbound line to the northbound line once the OHLE is extended?
Detraining ar Farringdon is impractical due to the width of the platform.

Would this change once Farringdon has been reconstructed in 2011? I
assume this depends on the answer to my second question.

I assume not. Widening this platform would mean a considerable
diversion of either LU or TL.


--
Peter Lawrence