GWR to lease ‘tri-mode’ class 769 multiple units from Porterbrook

[Artless Bodger]

Northmoor, yes, I accept your points, particularly if someone unwitingly wanders on to the track and is impacted. Insensitive comment removed.

Edited August 6, 2021 by Artless Bodger
Original insensitive comment removed

[Zomboid]

9 hours ago, Artless Bodger said:

On the Tyne and Wear Metro I notice that in some places the catenary support wire seems to be in effect a parallel second contact wire (e.g. along the Benton - South Gosforth stretch), I'm not sure if this is due to tight clearance, but presumably would double the current carrying capacity on that stretch

The catenary wire carries current in normal situations, though how much depends on what it's made of and how big it is (amongst other things). It may have more or less current carrying capacity then the contact wire.

 

In any case, a circuit is only as strong as it's weakest stretch (this is how fuses work), so whether it has any impact depends on where it is in relation to the substations.

[KeithHC]

So trying to get back to the subject. When are these units going to come in to service and have they been tested to Oxford yet.

 

Keith

[St. Simon]

Hi Keith,

 

They are being sent to Oxford for stabling, as Reading has run out of space because of the number of multi-coloured 387s that are there. So, in a way, they have been tested to Oxford. 

 

I have an in service date and initial routes, but I don’t think it’s in the public domain yet, so I can’t reveal it, but it’s Autumn into Winter this year, subject to testing and modifications.

 

Simon

[St. Simon]

Hi,

 

The introduction of these units is getting closer.

 

The first ‘sign’ of the introduction is the installation of Static Power Change-Over signage at Reading (and presumably at other stations, but I’ve only been to Reading so far!):

 

 

 

 

The Dynamic Power Change-Over Signage is still in development, albeit it at an advance stage. 
 

The trains themselves aren’t far off for a ‘soft’ launch, but still need some mods before full introduction.

 

Simon

Edited April 18, 2022 by St. Simon

[The Stationmaster]

There was one 769 set visible outdoors on Reading depot yesterday.

 

I'm not sure why 'dynamic changeover' signs need to be designed as such things were around on the national network almost 30 years ago!   They definitely need to be very carefully sited and that does require planning and site investigation.

[St. Simon]

2 hours ago, The Stationmaster said:

There was one 769 set visible outdoors on Reading depot yesterday.

 

I'm not sure why 'dynamic changeover' signs need to be designed as such things were around on the national network almost 30 years ago!   They definitely need to be very carefully sited and that does require planning and site investigation.

Hi Mike,

 

You’re right, we are using the same signage as Eurostar used, although slightly differently, so when I say ‘designed’, I mean the positioning and layout rather than what the signs look like.

 

Simon

[St. Simon]

5 minutes ago, St. Simon said:

Hi Mike,

 

You’re right, we are using the same signage as Eurostar used, although slightly differently.

 

Simon

Hi,

 

Having said that, there is a new standard coming that is formalising Power Change-Over Signage, which involves changing the meaning, slightly, of some existing signage and introducing new signage.

 

This is because we are having to use a very limited suite of signs for a wider variety of uses, so we need some more signs so that we don’t use signs inconsistently, particularly across the same region.

 

Simon

[balders]

10 hours ago, The Stationmaster said:

There was one 769 set visible outdoors on Reading depot yesterday.

 

I'm not sure why 'dynamic changeover' signs need to be designed as such things were around on the national network almost 30 years ago!   They definitely need to be very carefully sited and that does require planning and site investigation.

Been three or four knocking around Oxford sidings in the last three weeks and saw a couple at Reading this afternoon. Personally I think they look very smart..........re-engineering with that retro look. 

 

Can we have one in blue/pearl grey please......just, because

 

Regards

 

Guy

[phil-b259]

On 13/12/2021 at 21:19, St. Simon said:

Hi,

 

The introduction of these units is getting closer.

 

The first ‘sign’ of the introduction is the installation of Static Power Change-Over signage at Reading (and presumably at other stations, but I’ve only been to Reading so far!):

 

 

 

The Dynamic Power Change-Over Signage is still in development, albeit it at an advance stage. 
 

The trains themselves aren’t far off for a ‘soft’ launch, but still need some mods due fully introduction.

 

Simon

 

A shame the link across to the SR isn't electrified (on either system)

 

I guess that as with Acton Wells, the fact that it doesn't host a regular passenger service (most of the scheduled Reading - Gatwick runs will go from the SR platforms unless coming to / from Reading depot) means it doesn't pass the been counters BCR tests.

[Zomboid]

1 hour ago, phil-b259 said:

guess that as with Acton Wells, the fact that it doesn't host a regular passenger

I think some early/ late trains where the unit goes empty to/from the depot use the dive under from the high numbered platforms. That certainly used to be the case going the other direction to Basingstoke, and would make sense rather than a shunt into 4/5/6.

 

If Cross Country still run to Guildford then that'll use one of the connections too.

 

Edit - I should have read your post more carefully...

 

Either way, it would need to be a regular Didcot to Ascot train or something to justify it, because AC/DC interfaces are very expensive and complex. If it were just a matter of fitting a few skyhooks then the BCR would probably work out, but the fact that you must always earth AC tracks and the fact that you must not deliberately earth DC tracks makes the whole thing a nightmare. Fitting dual voltage trains with a 5km battery to get from one to the other is probably a better solution.

Edited December 15, 2021 by Zomboid

[The Stationmaster]

1 hour ago, phil-b259 said:

 

A shame the link across to the SR isn't electrified (on either system)

 

I guess that as with Acton Wells, the fact that it doesn't host a regular passenger service (most of the scheduled Reading - Gatwick runs will go from the SR platforms unless coming to / from Reading depot) means it doesn't pass the been counters BCR tests.

The Poplar Branch at Acton (up the bank to Acton Wells) was intended to be electrified as part of the Paddington - Heathrow scheme but survey work found that there was insufficient clearance under the Western Avenue overbridge.  So the alternative of lowering the track was duly considered but was found to be impossible because very close to the bridge there is a very large gas main underneath the formation and it was inadvisable to lower the track.

 

Just to be awkward I believe the replacement bridge in fact provides sufficient clearance but it post dates the electrification work by some years so no scheme was going on which could have the electrification up the bank tagged onto it.  It would inevitably have to have been electrified if the St. Pancras - Heathrow link proposal had ever happened but that never really stood much chance due to the need for it to incorporate major flyover works in order to access the Down Relief at Acton (although Crossrail has of course resulted in a diveunder at Acton).

[Zomboid]

Acton Wells really should have been done for the GWML scheme. Without that, the GWML has no electrified connection to the rest of the network. I'm sure one day it will be...

[phil-b259]

6 hours ago, The Stationmaster said:

 

Just to be awkward I believe the replacement bridge in fact provides sufficient clearance but it post dates the electrification work by some years so no scheme was going on which could have the electrification up the bank tagged onto it.  It would inevitably have to have been electrified if the St. Pancras - Heathrow link proposal had ever happened but that never really stood much chance due to the need for it to incorporate major flyover works in order to access the Down Relief at Acton (although Crossrail has of course resulted in a diveunder at Acton).

 

It could have been tagged onto the more recent GWML scheme as the bridge rebuild happened before GWML (beyond airport junction) electrification was announced.

 

Moreover even Railtrack manged to wire the NLL to WCML freight line (which bypasses Willesden Junction station) despite there not being any other electrification happening in the UK at the time so the 'need' for it to link directly to a line already undergoing electrification is a red herring.

 

No, the only reason it hasn't been done in recent years is the been counters do not believe it to be justified (with some justification) when in reality the lack of the useful links generally speaking presents a serious problem in pushing the use of electric traction for non passenger operations.

 

 

 

Edited December 15, 2021 by phil-b259

[phil-b259]

2 hours ago, Zomboid said:

 

Either way, it would need to be a regular Didcot to Ascot train or something to justify it, because AC/DC interfaces are very expensive and complex. If it were just a matter of fitting a few skyhooks then the BCR would probably work out, but the fact that you must always earth AC tracks and the fact that you must not deliberately earth DC tracks makes the whole thing a nightmare. 

 

You need to remember that even where 3rd rail stops then all equipment must be made DC proof for a minimum of 2 miles - and frequently further if long trains are operated. As such the whole of Reading station area will have needed to ensure it is suitably equipped against stray DC currents from the SWR lines.

 

There are also plenty of locations where AC and DC co-exist* (noting that the rails of the two don't have to be directly connected for stray DC currents to be an issue) already so its not as if its technically challenging to devise an engineering solution at a reasonable cost.

 

* List

City Thameslink - Farringdon  (and St Pancras if you factor in the parallel LU lines)

The West London Line

The WCML at Camden

Ebbsfleet

Ashford

Dollands Moor

Hunts Cross (Liverpool)

The H&C and the GWML on the approach to Paddington

The GE and the Central Line at Stratford

The LTSR and the District line out to Upminster

The DC line and the WCML.

 

[phil-b259]

3 hours ago, Zomboid said:

Fitting dual voltage trains with a 5km battery to get from one to the other is probably a better solution.

 

No space on the 769s to do that! (unless you scrap the diesel engines)

 

However it is true that in the longer term the use of battery technology could be used to overcome such gaps with regards passenger trains, though whether batteries could cope with the hilly Guildford - Reigate section is questionable at present.

 

More widely though, it is accepted by everyone with a brain that when it comes to freight, battery solutions simply don't have enough oomph and as such electrification remains the best way of decarbonising* that sector.

 

 

* Hydrogen is all very well but given that has been touted as the solution for everything from planes to cars and gas boilers, its madness to also use it for rail where electrification is a very practical way of delivering the same benefits.

[Zomboid]

The thing there is "reasonable cost". Yes, solutions exist, but for the handful of movements between the Southern and Western routes at Reading they're unlikely to be justifiable, especially when the services which would change over onward need on board power of some sort from Wokingham anyway. And not all of those examples are things that anyone would choose to repeat.

[Zomboid]

1 minute ago, phil-b259 said:

 

No space on the 769s to do that! (unless you scrap the diesel engines)

 

However it is true that in the longer term the use of battery technology could be used to overcome such gaps with regards passenger trains, though whether batteries could cope with the hilly Guildford - Reigate section is questionable at present.

 

More widely though, it is accepted by everyone with a brain that when it comes to freight, battery solutions simply don't have enough oomph and as such electrification remains the best way of decarbonising* that sector.

 

 

* Hydrogen is all very well but given that has been touted as the solution for everything from planes to cars and gas boilers, its madness to also use it for rail where electrification is a very practical way of delivering the same benefits.

I wasn't thinking of 769s specifically there. But to take a different example, if City Thameslink to Farringdon was unelectrified and the 700s had some limited battery capability to get between the two, the changeover would be orders of magnitude simpler.

 

There's no one size fits all solution of course. If dual voltage freight locomotives are part of the plan for a given route then you probably will need a changeover, but for other routes where the range of rolling stock is limited it may not be worthwhile.

[phil-b259]

6 minutes ago, Zomboid said:

I wasn't thinking of 769s specifically there. But to take a different example, if City Thameslink to Farringdon was unelectrified and the 700s had some limited battery capability to get between the two, the changeover would be orders of magnitude simpler.

 

Maybe - maybe not.

 

IIRC when checked prior to re-opening  stray DC currents were detected as far away as Kentish Town in the north while AC traction currents could be detected as far as Elephant & Castle in the south.

 

In other words its not just a case that the actual physical overlap of the OLE / con rail which matters....

[DY444]

2 hours ago, phil-b259 said:

 

You need to remember that even where 3rd rail stops then all equipment must be made DC proof for a minimum of 2 miles - and frequently further if long trains are operated. As such the whole of Reading station area will have needed to ensure it is suitably equipped against stray DC currents from the SWR lines.

 

There are also plenty of locations where AC and DC co-exist* (noting that the rails of the two don't have to be directly connected for stray DC currents to be an issue) already so its not as if its technically challenging to devise an engineering solution at a reasonable cost.

 

* List

City Thameslink - Farringdon  (and St Pancras if you factor in the parallel LU lines)

The West London Line

The WCML at Camden

Ebbsfleet

Ashford

Dollands Moor

Hunts Cross (Liverpool)

The H&C and the GWML on the approach to Paddington

The GE and the Central Line at Stratford

The LTSR and the District line out to Upminster

The DC line and the WCML.

 

 

Ealing Broadway

[The Stationmaster]

1 hour ago, DY444 said:

 

Ealing Broadway

And, already, at Reading station where £rd rail electrified and 25kv overhead are literally onluy a few feet apart (but no track circuits of course) 

 

3 hours ago, Zomboid said:

I wasn't thinking of 769s specifically there. But to take a different example, if City Thameslink to Farringdon was unelectrified and the 700s had some limited battery capability to get between the two, the changeover would be orders of magnitude simpler.

 

Simpler maybe but not, surely 'orders of magnitude'?  Changeover between one system of electrification and another - either while stationary or while moving at speed - has been around for a long while in everyday railway operation and usually amounts to nothing more than operating  2 or 3 switches in the correct order (and even some of that can be very easily dealt with automatically).  

 

The problem - as noted by Phil - is more a matter of stray currents finding their way between the two systems (and upsetting signalling equipment if they do anything at all).  Physically changing from one system to another is not really any different from changing to or from a battery supply - except in the case of Thameslink you only need to do it once as things currently stand rather than do it twice if you had a battery powered 'gap' between the two systems.

[Zomboid]

22 minutes ago, The Stationmaster said:

Simpler maybe but not, surely 'orders of magnitude'?

Farringdon is a unique case, there's a huge number of track circuits and rectifiers there to manage the changeover. It's vastly complicated.

[St. Simon]

Hi,

 

The other designer currently on 769 Dynamic PCO was, in a previous life, one of the Track PEs for the Reading remodelling, with particular responsibility for the Southern lines (he was the one who named Reading Southern Junction).

 

He has said in the past that there was discussion at the time of providing 3rd rail up from the Southern to the Western to allow Class 92s on operate all the way from the Chanel Tunnel up to the Midlands via Reading (although I think this a hypothetical scenario). However I think cost and actual need, plus the conditions at the bottom of the dive under meant that it didn’t go any further.

 

As for wiring Ealing Broadway to Acton Wells, that is in the cards as part of the Old Oak Common Station scope.

 

Simon

[St. Simon]

1 hour ago, The Stationmaster said:

Simpler maybe but not, surely 'orders of magnitude'?  Changeover between one system of electrification and another - either while stationary or while moving at speed - has been around for a long while in everyday railway operation and usually amounts to nothing more than operating  2 or 3 switches in the correct order (and even some of that can be very easily dealt with automatically).  

Hi Mike,

 

I think that the change-over information for Thameslink is now handled automatically using packet 39 in the E.T.C.S. movement authority / balise data.

 

Simon

[Zomboid]

1 hour ago, St. Simon said:

He has said in the past that there was discussion at the time of providing 3rd rail up from the Southern to the Western to allow Class 92s on operate all the way from the Chanel Tunnel up to the Midlands via Reading (although I think this a hypothetical scenario). However I think cost and actual need, plus the conditions at the bottom of the dive under meant that it didn’t go any further.

The DC all the way from Clapham Jn to Reading would need a lot of reinforcement to allow that, plus the air gap neutral section between Didcot and Coventry would cost a lot more than the AC/DC changeover in Reading