GWR Class 769 information. (Units no longer with GWR - Off Lease March 23)

[Invincible]

The GWR units usually run on AC between Didcot and Reading when sets are swapped between Reading TCD and Oxford sidings, and to come off Reading TCD for the Redhill runs, so they get some AC running on a semi-regular basis.

So the 769 will run AC between Didcot and Reading, DC Reading to Wokingham, diesel Wokingham to Redhill and DC Redhill to Gatwick?

From Modern railways 24th June 2022 Class 769 failure generates interference, which can be read if googled ,otherwise subscription only. Said a component failure caused 769 on AC to generate "electronic havoc" in Manchester so had to work diesel till fixed. The component has been changed, but the article says would have affected commissioning of the GWR units. Guess no testing this week Didcot to Gatwick due to the strike?

 

[norbitonflyer]

So the 769 will run AC between Didcot and Reading, DC Reading to Wokingham, diesel Wokingham to Redhill and DC Redhill to Gatwick?

Could run DC Reigate to Gatwick. Are there plans to run DC between Ash and Guildford as well (it's not far but would reduce noise/pollution in Guildford station itself)

 

[DelW]

Could run DC Reigate to Gatwick. Are there plans to run DC between Ash and Guildford as well (it's not far but would reduce noise/pollution in Guildford station itself)

Yes, see posts 1323 and 1326 for details.

 

[TurboMan]

Could run DC Reigate to Gatwick. Are there plans to run DC between Ash and Guildford as well (it's not far but would reduce noise/pollution in Guildford station itself)

Already happening. Towards Gatwick, it's Diesel to DC at Aldershot Sth then back to diesel at Guildford, towards Reading it's Diesel to DC at Shalford Jct then back to diesel at Ash.

== Doublepost prevention - post automatically merged: 25 Jul 2022 ==

So the 769 will run AC between Didcot and Reading, DC Reading to Wokingham, diesel Wokingham to Redhill and DC Redhill to Gatwick?

From Modern railways 24th June 2022 Class 769 failure generates interference, which can be read if googled ,otherwise subscription only. Said a component failure caused 769 on AC to generate "electronic havoc" in Manchester so had to work diesel till fixed. The component has been changed, but the article says would have affected commissioning of the GWR units. Guess no testing this week Didcot to Gatwick due to the strike?

Wednesday is cancelled due to the strike, and Monday cancelled to give the depot time to prepare units for a test of the ASDO system on Thursday/Friday. There's not much testing between Reading and Didcot, but they do run on AC between the two when a set swap is taking place between Oxford UCS and Reading TCD.

The issue at Manchester was down to a defective VCB. The GWR fleet was restricted to diesel and DC only while the cause of the incident was being investigated, but are back on AC too now.

 

[FenMan]

Already happening. Towards Gatwick, it's Diesel to DC at Aldershot Sth then back to diesel at Guildford, towards Reading it's Diesel to DC at Shalford Jct then back to diesel at Ash.

== Doublepost prevention - post automatically merged: 25 Jul 2022 ==


Wednesday is cancelled due to the strike, and Monday cancelled to give the depot time to prepare units for a test of the ASDO system on Thursday/Friday. There's not much testing between Reading and Didcot, but they do run on AC between the two when a set swap is taking place between Oxford UCS and Reading TCD.

The issue at Manchester was down to a defective VCB. The GWR fleet was restricted to diesel and DC only while the cause of the incident was being investigated, but are back on AC too now.

Meanwhile, I'm still looking forward to catching a train at my local station, which is surrounded by DC lines, to hear the "electric whine" as we pull off the platform. But, I'm not so looking forward to the low, and awful, Thameslink seats, which I suspect will still be in these units.

 

[TT-ONR-NRN]

Meanwhile, I'm still looking forward to catching a train at my local station, which is surrounded by DC lines, to hear the "electric whine" as we pull off the platform. But, I'm not so looking forward to the low, and awful, Thameslink seats, which I suspect will still be in these units.

I'm not looking forward to catching the train at North Camp and then trundling along at 25mph. This class has form.

 

[AM9]

I'm not looking forward to catching the train at North Camp and then trundling along at 25mph. This class has form.

Unless it's the linespeed, why do you think 25mph? I've travelled over 70mph in a class 769 and there was less noise than there would be with a 150 at that speed.

 

[Nicholas Lewis]

Meanwhile, I'm still looking forward to catching a train at my local station, which is surrounded by DC lines, to hear the "electric whine" as we pull off the platform. But, I'm not so looking forward to the low, and awful, Thameslink seats, which I suspect will still be in these units.

The one i saw at Redhill a few weeks ago at least had the GWR upholstery style used in the GWRs 387's

 

[Recessio]

Already happening. Towards Gatwick, it's Diesel to DC at Aldershot Sth then back to diesel at Guildford, towards Reading it's Diesel to DC at Shalford Jct then back to diesel at Ash.

== Doublepost prevention - post automatically merged: 25 Jul 2022 ==


Wednesday is cancelled due to the strike, and Monday cancelled to give the depot time to prepare units for a test of the ASDO system on Thursday/Friday. There's not much testing between Reading and Didcot, but they do run on AC between the two when a set swap is taking place between Oxford UCS and Reading TCD.

The issue at Manchester was down to a defective VCB. The GWR fleet was restricted to diesel and DC only while the cause of the incident was being investigated, but are back on AC too now.

VCB?

 

[Richard Scott]

VCB?

Vacuum Circuit Breaker I expect.

 

[Recessio]

Vacuum Circuit Breaker I expect.

Ahh thank you! I googled VCB and it came up with a Vietnamese bank. I'm guessing Vacuum Circuit Breaker is the more likely option...

 

[TurboMan]

Ahh thank you! I googled VCB and it came up with a Vietnamese bank. I'm guessing Vacuum Circuit Breaker is the more likely option...

Yes, Vacuum Circuit Breaker, sorry, I should have made that clear.

 

[Recessio]

Yes, Vacuum Circuit Breaker, sorry, I should have made that clear.

No worries, thank you.

Is there any detail on exactly what the VCB failure "electronic havoc" was? Was it serious enough to affect safety through signalling or something? I'm reminded of the 442s flipping signals when passing. Iirc, but could be incorrect, I think the traction on 465/466 also had interference problems at first... Or did it just blow some OLE fuses or something?

 

[AM9]

No worries, thank you.

Is there any detail on exactly what the VCB failure "electronic havoc" was? Was it serious enough to affect safety through signalling or something? I'm reminded of the 442s flipping signals when passing. Iirc, but could be incorrect, I think the traction on 465/466 also had interference problems at first... Or did it just blow some OLE fuses or something?

Just a guess but would a VCB have a failure mode where there is an insufficent (or no) vacuum around the breaker points meaning that under load there would be considerable flashover as the contacts separate. That would put large spikes onto both the OLE and back through the unit's transformer. Both might cause 'electronic havoc'. I presume that there was a similar issue with older (mostly MKI) EMUs which having air blast breakers (ABB) a failure in the air supply could cause significant electrical disruption.

 

[swt_passenger]

No worries, thank you.

Is there any detail on exactly what the VCB failure "electronic havoc" was? Was it serious enough to affect safety through signalling or something? I'm reminded of the 442s flipping signals when passing. Iirc, but could be incorrect, I think the traction on 465/466 also had interference problems at first... Or did it just blow some OLE fuses or something?

Arcing in the VCB causing electronic noise, thence affecting track circuits, according to August Modern Railways. Also pointed out the VCB is common hardware and in all 3xx EMUs up to the 322. I suppose that means it shouldn’t be seen as an issue directly associated with the 769 conversion process.

 

[Recessio]

Arcing in the VCB causing electronic noise, thence affecting track circuits, according to August Modern Railways. Also pointed out the VCB is common hardware and in all 3xx EMUs up to the 322. I suppose that means it shouldn’t be seen as an issue directly associated with the 769 conversion process.

I see, thank you. I don't have access to Modern Railways, appreciate it.

If it's in everything up to the 322 I'm surprised it's only now being an issue? Or was it just one unit, not a class-wide design flaw?

 

[Towers]

769938 on this morning's voyage.

 

[AM9]

I see, thank you. I don't have access to Modern Railways, appreciate it.

If it's in everything up to the 322 I'm surprised it's only now being an issue? Or was it just one unit, not a class-wide design flaw?

It's a failure mode of the on-board isolators and/or their control equipment. Breaking upwards of 40A* at a potential of 40kV peaks requires very fast moving contacts and some means of arc suppression. Early EMUs and locos used Air Blast Breakers (ABBs), where a high pressure blast of air from the compressors physically blew the ionised air in which the arc was forming 'sideways' thereby lengthening the path until there was insufficient transient voltage to sustain the arc.
Vacuum circuit breakers (VCBs) go the other way where the contacts are in an environment that is at a low enough pressure to not support an arc. No vacuum is perfect but for rail use, the combination of a relatively hard vacuum and fast moving contacts (which is why there is a loud bang when they operate) achieves reliable enough operation.
Either type of breaker can fail or even operate poorly which may expose the supply, load or local electrical environment (e.g. signalling equipment) to ElectroMagnetic Interference (EMI) that it's design wasn't fully able to endure. That is the essence of the world or ElectroMagnetic Compatibility (EMC) and is by law, central to modern designs of anything electrical both in the possibility of it emitting EMI or not being immune to it.

*This figure is the current being drawn at the time of opening the circuit, - 40A is typical for a 1MW MKIII EMU, a class 390 however can draw up to 250A on full power.

 

[Recessio]

It's a failure mode of the on-board isolators and/or their control equipment. Breaking upwards of 40A* at a potential of 40kV peaks requires very fast moving contacts and some means of arc suppression. Early EMUs and locos used Air Blast Breakers (ABBs), where a high pressure blast of air from the compressors physically blew the ionised air in which the arc was forming 'sideways' thereby lengthening the path until there was insufficient transient voltage to sustain the arc.
Vacuum circuit breakers (VCBs) go the other way where the contacts are in an environment that is at a low enough pressure to not support an arc. No vacuum is perfect but for rail use, the combination of a relatively hard vacuum and fast moving contacts (which is why there is a loud bang when they operate) achieves reliable enough operation.
Either type of breaker can fail or even operate poorly which may expose the supply, load or local electrical environment (e.g. signalling equipment) to ElectroMagnetic Interference (EMI) that it's design wasn't fully able to endure. That is the essence of the world or ElectroMagnetic Compatibility (EMC) and is by law, central to modern designs of anything electrical both in the possibility of it emitting EMI or not being immune to it.

*This figure is the current being drawn at the time of opening the circuit, - 40A is typical for a 1MW MKIII EMU, a class 390 however can draw up to 250A on full power.

Thank you for the very detailed explanation!

 

[Benjwri]

Saw 769930 and 769959 at Oxford station today, headed to Reading Traincare. 769959 was badly graffitied, believe this might have been to take it for cleaning as 769930 returned an hour later with 769943 in tow this time. 769959 was hidden behind the sleeper when I went past Reading Traincare later.

 

[FGW_DID]

Saw 769930 and 769959 at Oxford station today, headed to Reading Traincare. 769959 was badly graffitied, believe this might have been to take it for cleaning as 769930 returned an hour later with 769943 in tow this time. 769959 was hidden behind the sleeper when I went past Reading Traincare later.

Should have been a double swap with 930 & 959 > RG, 938 & 943 > Oxford but 938 had a few faults found on prep that couldn’t be rectified in time so 930 was just sent back to Oxford with 943.

 

[FenMan]

Should have been a double swap with 930 & 959 > RG, 938 & 943 > Oxford but 938 had a few faults found on prep that couldn’t be rectified in time so 930 was just sent back to Oxford with 943.

I do wonder who is paying for this (non) performance of one the slowest roll-outs I've ever seen. None of the interested parties seem to be much fussed by the glacially slow process, so why do I suspect it's us taxpayers who are paying to keep this "enterprise"* afloat and not them?

*"Enterprise" is the kindest term I could think of. Insert your own words of choice.

 

[Southern Dvr]

I think we all know it’s us taxpayers footing the bill. I’m inclined to start looking for any connections between government and ‘the enterprise’ to figure out why this hasn’t been dropped in the bin as fast as the 442s were and indeed as fast as Southern’s recently refurbished 455s!

 

[Snow1964]

I think we all know it’s us taxpayers footing the bill. I’m inclined to start looking for any connections between government and ‘the enterprise’ to figure out why this hasn’t been dropped in the bin as fast as the 442s were and indeed as fast as Southern’s recently refurbished 455s!

Probably lack of alternative stock is keeping project going, both 442s and 455s were used in commuter areas so other fleets could be stretched to cover their withdrawal.

GWR is suffering overcrowding in Wiltshire, Avon, Gloucestershire etc so desperately needs the units which haven’t been released. Unlike the commuter franchises with shrinking numbers, GWR seems to have a growing leisure traffic.

I suspect the 769 project would be abandoned if GWR could find about 20-25 alternative trains with diesel (or bi-mode) power. Not that I can think of any suitable stock lying idle anywhere.

 

[JonathanH]

I suspect the 769 project would be abandoned if GWR could find about 20-25 alternative trains with diesel (or bi-mode) power. Not that I can think of any suitable stock lying idle anywhere.

Every day that training is deferred on the 769s is another day closer to stock becoming available that could be used in the west instead of the LTV 165s though.

 

[Clarence Yard]

I suspect the 769 project would be abandoned if GWR could find about 20-25 alternative trains with diesel (or bi-mode) power. Not that I can think of any suitable stock lying idle anywhere.

It will be the DfT who will have to find the stock as they are in charge of rolling stock cascades now. That is one reason why the GWR 769 project is still live - they are effectively paying for it.

 

[DelW]

It will be the DfT who will have to find the stock as they are in charge of rolling stock cascades now. That is one reason why the GWR 769 project is still live - they are effectively paying for it.

Which means, of course, that we taxpayers are funding the whole sorry farrago.
No wonder none of the supposedly interested parties are actually doing much about getting these trains into service, why bother when taxpayers are footing everyone's bills? Just send one train to Gatwick and back three days a week and pretend that's an exercise with some point to it.
Sometime in the future the endless stream of taxpayers' money will be cut back at source, and "the railway" is likely to find that a painful experience. It's possible that these units will then go for scrap without ever entering post-rebuild service, just as the 442s did - another monumental waste of other people's money.

 

[Nicholas Lewis]

Which means, of course, that we taxpayers are funding the whole sorry farrago.
No wonder none of the supposedly interested parties are actually doing much about getting these trains into service, why bother when taxpayers are footing everyone's bills? Just send one train to Gatwick and back three days a week and pretend that's an exercise with some point to it.
Sometime in the future the endless stream of taxpayers' money will be cut back at source, and "the railway" is likely to find that a painful experience. It's possible that these units will then go for scrap without ever entering post-rebuild service, just as the 442s did - another monumental waste of other people's money.

DfT have culled plenty of other trains as well as turning the screws on non essential TOC expenditure but have yet to cull this project. Guess someone at GWR is giving them confidence to stick with it.

 

[3141]

Which means, of course, that we taxpayers are funding the whole sorry farrago.
No wonder none of the supposedly interested parties are actually doing much about getting these trains into service, why bother when taxpayers are footing everyone's bills? Just send one train to Gatwick and back three days a week and pretend that's an exercise with some point to it.
Sometime in the future the endless stream of taxpayers' money will be cut back at source, and "the railway" is likely to find that a painful experience. It's possible that these units will then go for scrap without ever entering post-rebuild service, just as the 442s did - another monumental waste of other people's money.

Of course, taxpayers are funding the whole railway. I doubt that anybody at GWR or Porterbrook is saying "we don't actually need to do much about getting these trains into service when taxpayers are footing everyone's bills". I'd guess that Porterbrook, GWR, Northern and TfW would like the 769s to work. The TOCs are probably counting the days till new stock arrives to replace them (TfW) or existing stock becomes available from elsewhere (Northern and GWR) - as suggested a few posts earlier. Material for a speculative thread there. We know that Northern have had some pretty direct discussions with Porterbrook, and it wouldn't be surprising if there's been some tough talking behind the scenes at GWR as well.

 

[zwk500]

Sometime in the future the endless stream of taxpayers' money will be cut back at source, and "the railway" is likely to find that a painful experience.

The recent strikes indicate that point was reached a few months ago.