GWML Electification

[phil-b259]

12 minutes ago, Edwin_m said:

 

He said...

 

Please note Simons wording. He quite clearly states Bristol has NOT been subject to a resignalling scheme as such.

 

Within the industry the term 'resignalling' has a quite specific meaning, namely a 'big bang' / total replacement of everything situation. By contrast where lesser alterations are made words like 're-control', 're-lock' will be used as appropriate. Like for like conversion of equipment like track circuits doesn't count as a 'resignalling' either - even if it happens alongside other elements such as a re-control.

 

For example, to the lay-person the alterations which took place at Redhill (Surrey) to provide a extra through platform might seem like a 'resignalling' - but the reality is it was simply a modification to the existing geographical relay interlocking modified to control the revised layout which mostly remained completely unchanged.

 

The replacement of Kings cross interlocking a decade or so ago was a 're-lock', not a resignalling.

 

Reading was obviously resignalled as part of the rebuild, but the Newbury area would have simply been a 're-control'. Modifications to non AC immune track circuits would not be resignalling - but would be done under a 'AC immunisation' project

 

Obviously it is your prerogative to call the Bristol alterations what you want - but as someone interested in the specifics its fairly clear to me that the modifications done at Bristol thus far cannot be termed a 'resignalling' of the area.

 

 

 

 

[caradoc]

14 hours ago, Arun Sharma said:

I had an idea that Chiltern wanted to extend their Marylebone to Oxford service by having trains continue past Oxford to Kennington Junction, Littlemore and Cowley. That would have involved extending the present Platform 1 running line through the present booking office(!) so is the remodelling of Oxford really now considered finished?

 

The through Chiltern service has indeed been suggested, but I'm not sure that providing an extra through line on the Up side would be necessary for it; Current (pre-Covid) off-peak use per hour of the through platforms is IIRC, 2 GWR London expresses, 2 GWR Didcot stoppers, and 2 Cross-countries, so an extra two trains an hour, carefully timetabled, would not be impossible with the existing layout, and an additional through platform on the Down side would certainly add flexibility. Personally, while I know there were valid reasons against it, I still believe the easier solution would have been two or three terminal platforms on the Up side south of the Botley Road underbridge, on the site of the car park, so that anything from the south terminating at Oxford would not have to use the through platforms at all. 

 

 

[Nick Gough]

21 hours ago, The Stationmaster said:

...

Incidentally a couple of days ago I drove along the road which roughly parallels the railway between north and south stoke - where the ohle structures were the ones that prompted the start of the 'Goring moans'  with photos featured in several places to show how bad they were.  They were not at all noticeable looking across from the road (although might be a bit more obvious once the leaves are of the trees which stand behind them when viewed from the north.

 

I think this is where you mean? Taken a couple of weeks ago near the turning for South Stoke.

 

And a couple of closer views:

[Edwin_m]

3 hours ago, phil-b259 said:

 

Please note Simons wording. He quite clearly states Bristol has NOT been subject to a resignalling scheme as such.

 

Within the industry the term 'resignalling' has a quite specific meaning, namely a 'big bang' / total replacement of everything situation. By contrast where lesser alterations are made words like 're-control', 're-lock' will be used as appropriate. Like for like conversion of equipment like track circuits doesn't count as a 'resignalling' either - even if it happens alongside other elements such as a re-control.

 

For example, to the lay-person the alterations which took place at Redhill (Surrey) to provide a extra through platform might seem like a 'resignalling' - but the reality is it was simply a modification to the existing geographical relay interlocking modified to control the revised layout which mostly remained completely unchanged.

 

The replacement of Kings cross interlocking a decade or so ago was a 're-lock', not a resignalling.

 

Reading was obviously resignalled as part of the rebuild, but the Newbury area would have simply been a 're-control'. Modifications to non AC immune track circuits would not be resignalling - but would be done under a 'AC immunisation' project

 

Obviously it is your prerogative to call the Bristol alterations what you want - but as someone interested in the specifics its fairly clear to me that the modifications done at Bristol thus far cannot be termed a 'resignalling' of the area.

 

 

 

 

I'm very aware of these differences.  I was the project engineer for the IECC system that first enabled large-scale "re-control".  

 

In the context of this thread it's irrelevant.  The question was whether Bristol is now AC immune and we have the answer that it is.  This almost certainly means it was more than re-control or re-locking, some replacement of trackside equipment must have taken place.  

[96701]

I'll just leave this here: 

Bristol Area Signalling Renewals and Enhancements (BASRE)

 

I will also leave this here so that people who are really interested can compare and contrast.

 

Cardiff Area Signalling Renewal (CASR)

[DY444]

18 hours ago, phil-b259 said:

 

Please note Simons wording. He quite clearly states Bristol has NOT been subject to a resignalling scheme as such.

 

Within the industry the term 'resignalling' has a quite specific meaning, namely a 'big bang' / total replacement of everything situation. By contrast where lesser alterations are made words like 're-control', 're-lock' will be used as appropriate. Like for like conversion of equipment like track circuits doesn't count as a 'resignalling' either - even if it happens alongside other elements such as a re-control.

 

For example, to the lay-person the alterations which took place at Redhill (Surrey) to provide a extra through platform might seem like a 'resignalling' - but the reality is it was simply a modification to the existing geographical relay interlocking modified to control the revised layout which mostly remained completely unchanged.

 

The replacement of Kings cross interlocking a decade or so ago was a 're-lock', not a resignalling.

 

Reading was obviously resignalled as part of the rebuild, but the Newbury area would have simply been a 're-control'. Modifications to non AC immune track circuits would not be resignalling - but would be done under a 'AC immunisation' project

 

Obviously it is your prerogative to call the Bristol alterations what you want - but as someone interested in the specifics its fairly clear to me that the modifications done at Bristol thus far cannot be termed a 'resignalling' of the area.

 

At Bristol TM a number of GPLs were removed, all the point mechanisms and running signals were replaced and some extra ones added to replace the St. Andrew's crosses, all the track circuits were replaced by axle counters, all the interlockings were replaced and the whole lot was put into the TVSC. 

 

I don't want to engage in an argument about what constitutes resignalling and what doesn't but merely observe that many schemes with equivalent or lesser scope have been officially described as such in the past.

[rodent279]

4 minutes ago, DY444 said:

 

At Bristol TM a number of GPLs were removed, all the point mechanisms and running signals were replaced and some extra ones added to replace the St. Andrew's crosses, all the track circuits were replaced by axle counters, all the interlockings were replaced and the whole lot was put into the TVSC. 

 

I don't want to engage in an argument about what constitutes resignalling and what doesn't but merely observe that many schemes with equivalent or lesser scope have been officially described as such in the past.

What did it replace? Was the interlocking an SSI, or was it relay based?

[DY444]

11 minutes ago, rodent279 said:

What did it replace? Was the interlocking an SSI, or was it relay based?

 

I believe all the replaced interlockings were E10k freewired RRIs

[rodent279]

41 minutes ago, DY444 said:

 

I believe all the replaced interlockings were E10k freewired RRIs

I won't pretend that I know what that is, but I guess it means it was relay based, and hard wired

[DY444]

27 minutes ago, rodent279 said:

I won't pretend that I know what that is, but I guess it means it was relay based, and hard wired

 

Yes it's a relay interlocking. 

 

Freewired refers to the predominant underlying architecture of the interlocking which is a very complicated subject but in very simple terms a relay interlocking can be made up of a number of interconnected factory wired standard modules which provide specific functions (this is called geographical) or built up from more elemental components such as individual relay sets wired together on site (this is called freewired). 

 

There are pros and cons of both approaches and different regions had different requirements and preferences.  The WR tended to favour freewired and used it extensively in their late 60s and early 70s resignalling schemes.

[jamie92208]

1 hour ago, DY444 said:

 

Yes it's a relay interlocking. 

 

Freewired refers to the predominant underlying architecture of the interlocking which is a very complicated subject but in very simple terms a relay interlocking can be made up of a number of interconnected factory wired standard modules which provide specific functions (this is called geographical) or built up from more elemental components such as individual relay sets wired together on site (this is called freewired). 

 

There are pros and cons of both approaches and different regions had different requirements and preferences.  The WR tended to favour freewired and used it extensively in their late 60s and early 70s resignalling schemes.

In 1971 I had a tour of Trent Junction PSB. IIRC the relay room was at least twice the size of the control room upstairs.  Whilst we were downstairs a route was set up from Nottingham Station to Loughborough. We saw the lights some on on the maintainers panel then heard the relays start clicking and could follow the route round the room by the sound as they were arranged geographically.  Fabulous to see and listen to.

 

Jamie

[ess1uk]

On 01/10/2020 at 12:09, SouthernMafia said:

An interesting development found buried away in the GWR internal weekly newsletter:

 

"We are working with NR to secure the funding to progress the development of electrification between Acton Wells Junction and Acton West Junction (aka The Poplars) and between Didcot and Oxford, extending to Hanborough. This has been approved at the Great Western & Wales Programme Board and we waiting for are wider Government sign-off to release the funds.   "

 

I'm not sure how the Poplar is of any interest to GWR 

Are those lines not Anglia?

[corneliuslundie]

The GER had only one Poplar.

These are in West London. I don't have a modern map but I suspect that they on the former North & South Western Junction line

Jonathan

[Edwin_m]

3 hours ago, jamie92208 said:

In 1971 I had a tour of Trent Junction PSB. IIRC the relay room was at least twice the size of the control room upstairs.  Whilst we were downstairs a route was set up from Nottingham Station to Loughborough. We saw the lights some on on the maintainers panel then heard the relays start clicking and could follow the route round the room by the sound as they were arranged geographically.  Fabulous to see and listen to.

 

Jamie

At the risk of encouraging a tangent I should point out that the relay room at Trent was unusually large relative to the control room.  Trent and Saltley had all their interlocking housed centrally, connecting to the track by vital frequency division multiplex.  Every other power box had several smaller interlockings, each located in a building near, and hard-wired to, the track it controlled.  All these except the one in the power box itself were connected back to the panel by non-vital time division multiplex.  So the interlocking downstairs in the box itself only controlled the immediate vicinity and was therefore smaller. 

 

Getting back on topic, I think the Temple Meads interlocking would also have been hardwired to its panel upstairs, and if so any sort of re-control would have been difficult as each wire would have needed to be diverted to a new interface.  

 

As far as I know the Temple Meads power box is still there and still controls some track west of the station which was never included in the electrification.  If the northern trainshed was ever to be brought back into use, this remaining area would need some form of re-signaling so the power box could be demolished.  

[Mike_Walker]

59 minutes ago, corneliuslundie said:

The GER had only one Poplar.

These are in West London. I don't have a modern map but I suspect that they on the former North & South Western Junction line

Jonathan

The incline between Action Main Line (actually Poplar Line Junction) on the GWML and Acton Wells Junction on the N&SWJ are designated the Poplar Lines and have been since they were built. The name comes from them being the way the GWR accessed the North London Lines to reach its goods depot within the docks at Poplar.

 

Wiring them would be of little use to today's GWR apart from allowing 387s to get to Bombardier's Ilford works under their own power but it would be useful for through freight services. I can't see any justification for extend the OLE from Oxford to Handborough.

 

On the subject of PSBs, the first floor room that housed Swindon Panel (and that it lives in today at Didcot) was roughly the equivalent of a quarter of the building's footprint and around three quarters of the ground floor was occupied by the relay interlocking. But that wasn't all, there were around a dozen remote interlockings at places such as Wootton Bassett.

 

In addition to the sound of the relays working, the most noticeable thing was the distinctive aroma given off which would even permeate to the operating floor - something we haven't managed to replicate at Didcot.

[keefer]

3 hours ago, Mike_Walker said:

Wiring them would be of little use to today's GWR apart from allowing 387s to get to Bombardier's Ilford works under their own power but it would be useful for through freight services

Incidentally, what's the capacity of the OLE like after Acton Wells Jcn? Given there's an intensive passenger service now on the NLL/WLL, is there enough juice in the wires to cope with electric-hauled freight too?

And linked to that, do/can any of the modern units use regen braking to put some energy back into the system - I'm sure I've read that some relatively recent schemes were built to a price and can't handle the extra load unless there's another train nearby that can use the power being put back in.

[Zomboid]

13 minutes ago, keefer said:

Incidentally, what's the capacity of the OLE like after Acton Wells Jcn?

There's plenty of power unless one of the supplies is unavailable, is the short answer.

 

The long answer is that there's a feeder station near Willesden Junction with one transformer for the NLL and one for the WCML, and they back each other up, so if it's only supplying the NLL there's loads of capacity. There's a third transformer there which used to feed the GWML at OOC, but that's been superseded by a much bigger supply. That supply could be brought back relatively simply (it's not a new connection) to provide more resilience to the NLL/ WCML if necessary.

[Zomboid]

3 hours ago, Mike_Walker said:

I can't see any justification for extend the OLE from Oxford to Handborough

Presumably having the power change over away from Oxford station will offer operational benefits. Hanborough itself isn't much of a place to terminate an electric service.

[rodent279]

9 hours ago, DY444 said:

 

Yes it's a relay interlocking. 

 

Freewired refers to the predominant underlying architecture of the interlocking which is a very complicated subject but in very simple terms a relay interlocking can be made up of a number of interconnected factory wired standard modules which provide specific functions (this is called geographical) or built up from more elemental components such as individual relay sets wired together on site (this is called freewired). 

 

There are pros and cons of both approaches and different regions had different requirements and preferences.  The WR tended to favour freewired and used it extensively in their late 60s and early 70s resignalling schemes.

Ah I see. So a geographical interlocking is a series of functional modules that can be connected together as required, rather like plugging ic's into a circuit board, whereas in a freewired interlocking every connection is made individually?

[phil-b259]

1 hour ago, rodent279 said:

Ah I see. So a geographical interlocking is a series of functional modules that can be connected together as required, rather like plugging ic's into a circuit board, whereas in a freewired interlocking every connection is made individually?

 

Sort of - but significantly larger.

 

Here are some photos of a 'WestPac' Geographical interlocking by Westinghouse*. Note that those relays (which are officially called 'BR 930 Series miniature relays'** are not exactly small - and a Westpack module can contain anything from 12 to 48 of the things depending on the function the module has been designed to perform. They are linked together by colour coded plug couplers and the individual functions are passed from pack to pack.

 

However because no two locations are the same, each Geographical interlocking requires a certain amount of 'freewire' (i.e. yet more relays to tune each pack) to make it respond as required for that particular site. In the photos the 'freewire' occupies the top row with Westpac modules on the middle and bottom rows

 

Some electrical feeds start at the 'first pack and run through to the last, others from from the last to the first and some require feeds from both ends to meet in the middle. Each module will also have further plug couplers to interface with the freewire above it and to extract certain electrical circuits to the outside world.

 

The original idea was that faults would be traced to each pack and the whole pack unplugged, swapped for a fresh one and the defective one sent back to Westinghouse for repair. Aside from the fact the packs are incredibly heavy thanks to all the relays and metal chassis - doing this would cost a fortune and so replacement of individual relays within the pack was soon sanctioned.

 

* This is a training setup and a real Westpac interlocking would consist of many more racks of modules

 

**I kid you not - and if you compare them to the relays the railways used in the 1930s / 1940s then they are sort of miniature

Edited October 3, 2020 by phil-b259

[phil-b259]

8 hours ago, jamie92208 said:

In 1971 I had a tour of Trent Junction PSB. IIRC the relay room was at least twice the size of the control room upstairs.  Whilst we were downstairs a route was set up from Nottingham Station to Loughborough. We saw the lights some on on the maintainers panel then heard the relays start clicking and could follow the route round the room by the sound as they were arranged geographically.  Fabulous to see and listen to.

 

Jamie

 

There is something quite satisfying about a traditional relay room - the large quantity of relays clicking as signallers set routes being a tangible reminder of the complexity of the system.

 

It also provides a good brain workout when things go wrong - while in principle its a simple choice of tracking a voltage till you lose it (or working through till you find one) its actually a lot harder to do in practice. Of course the more tricky it is of course the better it feels when you get to the bottom of the issue - simply replacing a computer card just doesn't come close.

 

I guess the same could be said about a busy mechanical box too with the movement of levers, locking in the locking tray, etc or even the way a steam loco with all those connecting rods always seems to convey an image of brute force.

 

The modern idea of a computer driven railway with nothing more than a bunch of flashing LEDs and the hum of computer fans just doesn't have the same gravitas as it were....

[jamie92208]

52 minutes ago, phil-b259 said:

 

There is something quite satisfying about a traditional relay room - the large quantity of relays clicking as signallers set routes being a tangible reminder of the complexity of the system.

 

It also provides a good brain workout when things go wrong - while in principle its a simple choice of tracking a voltage till you lose it (or working through till you find one) its actually a lot harder to do in practice. Of course the more tricky it is of course the better it feels when you get to the bottom of the issue - simply replacing a computer card just doesn't come close.

 

I guess the same could be said about a busy mechanical box too with the movement of levers, locking in the locking tray, etc or even the way a steam loco with all those connecting rods always seems to convey an image of brute force.

 

The modern idea of a computer driven railway with nothing more than a bunch of flashing LEDs and the hum of computer fans just doesn't have the same gravitas as it were....

Perhaps it was that experience that gave me a love of relays that I like to use on my layout. I won't take the us any further off topic but I will post a couple of pictures on my layout thread that's in my signature below.

In the meantime I look forward to hearing positive news about the spread of the overhead wires.

 

Jamie

[Edwin_m]

1 hour ago, phil-b259 said:

**I kid you not - and if you compare them to the relays the railways used in the 1930s / 1940s then they are sort of miniature

A BR930 is 135 by 57 by 175mm according to a quick search.  About the size of a couple of paperbacks.  

[rodent279]

37 minutes ago, Edwin_m said:

A BR930 is 135 by 57 by 175mm according to a quick search.  About the size of a couple of paperbacks.  

Aye, I know the the word "miniature" was used in a relative sense! I have seen the real thing a couple of times. To me, miniature is anything under a cm or so!

I guess they are built for reliability, robustness and longevity in service, rather than space saving.

[iands]

12 hours ago, phil-b259 said:

 

There is something quite satisfying about a traditional relay room - the large quantity of relays clicking as signallers set routes being a tangible reminder of the complexity of the system.

 

It also provides a good brain workout when things go wrong - while in principle its a simple choice of tracking a voltage till you lose it (or working through till you find one) its actually a lot harder to do in practice. Of course the more tricky it is of course the better it feels when you get to the bottom of the issue - simply replacing a computer card just doesn't come close.

 

I guess the same could be said about a busy mechanical box too with the movement of levers, locking in the locking tray, etc or even the way a steam loco with all those connecting rods always seems to convey an image of brute force.

 

The modern idea of a computer driven railway with nothing more than a bunch of flashing LEDs and the hum of computer fans just doesn't have the same gravitas as it were....

I couldn't agree more Phil about the sounds a smells of relay rooms and mechanical signal boxes. I would also add that there is something special about the sounds of a Strowger telephone exchange; 2-motion selectors stepping through the banks, uni-selectors whirring away and the relays chattering away in the relay sets, you become quite attuned to the melodic sound - and you can instantly hear when a selector goes out of adjustment - akin to a bag of spanners being rattled at the back of an orchestra. All lost when 'Electronic Exchanges' became the norm. However, even they're being replaced now by 'Data Switches' to support computing and the internet as the main communication mode rather than "speech" - funny how things change over time.

However, going seriously off topic, apologies for that.