GWR 802s to Plymouth - Where do they switch from Electric to Diesel?

[jhy44]

Hi there,

After travelling from Paddington to Plymouth and back this weekend, I tried to notice when the train switched from electric to diesel, and vice versa on the return, but could not.

The outward stopped at Newbury, the return ran express from Taunton to Reading.

Does the train pan-up/down whilst moving? Aka, would the return leg have panned-up somewhere around Newbury, or would it have ran into Reading on Diesel and then panned up?

 

[Energy]

The bimode Hitachis can change between diesel and electric while moving.

 

[irish_rail]

Pan up and down is on the move just to the east of newbury racecourse station.

 

[pdeaves]

Under normal circumstances the change is Newbury (on the move)

 

[ainsworth74]

It amuses me somewhat they we've had people ask this question many times (no slight against the OP intended! It isn't obvious and so there's absolutely nothing wrong with asking the question!!). To hear it told before they were in service this should never have been a question as people were guaranteed to be deafened by the engines

 

[brad465]

The Video125 film from Exeter to London on an 802 service does reveal as said above the Racecourse location as the on the move changeover point, where the narrator also reveals that if down train drivers forget to drop the pantograph, it will be done for them. This is also where the 110mph line speed begins going west, so while it won't make much difference I suspect going from 100 to 110 on the move has to be done on the slower diesel, not electric.

 

[paul1609]

It amuses me somewhat they we've had people ask this question many times (no slight against the OP intended! It isn't obvious and so there's absolutely nothing wrong with asking the question!!). To hear it told before they were in service this should never have been a question as people were guaranteed to be deafened by the engines

And me and of course then you had all the Rail Industry informed sources who said they wouldnt be able to get over the Devon Banks

 

[Starmill]

I think the confusion sometimes arises because some companies (e.g. TransPennine Express) didn't allow changeovers while moving. I don't know if that's still the case there. The rolling stock is quite capable of it.

 

[Mollman]

I think the confusion sometimes arises because some companies (e.g. TransPennine Express) didn't allow changeovers while moving. I don't know if that's still the case there. The rolling stock is quite capable of it.

It is often to do with the infrastructure too. The OHLE at Colton Jnc isn't designed for trains panning up on the move so the swap over is done at York. Presume to keep it simple it is done in reverse there too. This has also been an issue in Greater Anglia with the new bi-modes. Extending the electrification to Church Fenton will include OHLE designed for pan-up on the move meaning the change over location for TPE Bi-modes (and the daily Leeds - Aberdeen Azuma) will move southwards.

 

[pdeaves]

It is often to do with the infrastructure too.

That's right. The wiring has to be specially designed to cope with a 'sudden whack' for raising the pan at speed. When stationary, the whack is a lot gentler. Thus, changeover on the move can only be done at certain places.

 

[Starmill]

Good point. Hambleton Jn is another one where that question has been raised. Is that one where trains towards Hull can drop the pan but trains from Hull can't raise it until Doncaster? Or something like that?

Presumably in the cases of the routes used by the GWR electro-diesel fleet the infrastructure has been specially installed to accommodate this?

 

[sjm77]

Good point. Hambleton Jn is another one where that question has been raised. Is that one where trains towards Hull can drop the pan but trains from Hull can't raise it until Doncaster? Or something like that?

Sorry to be a pedant but I think you mean Temple Hirst Jcn. Hambleton Jcns are west of Selby. I wish I could answer your question now but sadly cannot!

 

[hexagon789]

Good point. Hambleton Jn is another one where that question has been raised. Is that one where trains towards Hull can drop the pan but trains from Hull can't raise it until Doncaster? Or something like that?

Presumably in the cases of the routes used by the GWR electro-diesel fleet the infrastructure has been specially installed to accommodate this?

Yes, I believe the OLE is deliberately strengthened in specific locations on the Western to allow linespeed pan-ups. Otherwise there is a hefty speed restriction for raising the pan anywhere else, trying to remember the figure...

 

[DidcotDickie]

Yes, I believe the OLE is deliberately strengthened in specific locations on the Western to allow linespeed pan-ups. Otherwise there is a hefty speed restriction for raising the pan anywhere else, trying to remember the figure...

No it isn't, that myth regularly appears. It's the same tension throughout the GWML Series 1 electrification (which is higher than used elsewhere in the UK). The locations simply have to be plain line wire - no overlaps, neutral sections or junctions. They are at specific locations so that NR can monitor wire wear and condition more closely than elsewhere. Raising the pan at other locations is only permitted below 20mph I believe.

 

[Starmill]

Sorry to be a pedant but I think you mean Temple Hirst Jcn. Hambleton Jcns are west of Selby. I wish I could answer your question now but sadly cannot!

Ah sorry. I'd got confused because of a recent conversation elsewhere about trains going to Harrogate. That is indeed what I was thinking.

 

[MotCO]

At what point do the diesel engines need to be started, or are they always on but only ticking over?

 

[DidcotDickie]

At what point do the diesel engines need to be started, or are they always on but only ticking over?

They are usually started shortly before the traction changeover. They are switched off when running on electric.

It's a while since I've been on an 80x doing a traction change but IIRC, westbound Oxford fasts (not stopping at Didcot) would have the engines running between Goring and Cholsey for the switch to the non-wired avoiding lines at Didcot East Junction. Further west, trains to Bath and Bristol TM have the diesels running between Wootton Bassett and Christian Malford for where the wires run out east of Chippenham.

 

[MotCO]

They are usually started shortly before the traction changeover. They are switched off when running on electric.

I assume that the driver needs to do this - it is not automatically done like with the pans which are dropped if the driver forgets. Are there any examples of the driver forgetting to start the engine, or if the engine fails to start?

 

[DidcotDickie]

I assume that the driver needs to do this - it is not automatically done like with the pans which are dropped if the driver forgets. Are there any examples of the driver forgetting to start the engine, or if the engine fails to start?

Good question - there is a system called APCO (Automated Power ChangeOver) which works using lineside balises (beacons) which signals to the train to change traction mode (and which mode to change to). However, from what I've read from informed insiders elsewhere, most traction changes on the GWML are performed by the driver. I believe that APCO can intervene if, say, a driver forgets to lower the pantograph (so-called 'kill' balise) so there is some driver backup.

The only instance I recall of a driver forgetting to lower the pantograph at the end of a wire run occurred in the early days of testing the 80x, well before GWML electrification was put into passenger use. The first section of OLE to be energised was between Tilehurst (W of Reading) and Didcot and this was used as a test section for both trains and OLE. The 80x were being tested by GBRf drivers between Didcot and Reading but had to switch to diesel when eastbound as there was a gap between Tilehurst East Junction and Scours Lane on the recently completed flyover as the OLE was still being erected in the Reading station area. One driver unfortunately failed to lower the pantograph in time when passing eastbound through Tilehurst and it was removed by the first portal at Scours Lane on the uncompleted section of OLE. Presumably the Automated Device Drop (ADD - automatically lowers the pantograph if it goes overheight, as it would at the end of the wire run) didn't have time to operate in the short gap between OLE sections. There were some photos posted on Twitter of Hitachi staff sawing off the mangled remains of the pantograph on the unit in Reading station. The rest of it was located on the flyover.

 

[route101]

I never noticed the changover when i was on GWR, i suppose if your in the motor coach you would. To me being on a diesel train feels heavier compared to electric.

 

[4REP]

I think the confusion sometimes arises because some companies (e.g. TransPennine Express) didn't allow changeovers while moving. I don't know if that's still the case there. The rolling stock is quite capable of it.

Last week I saw a class 802 TP Arrive in Leeds with pan up coming from the York direction so they have been panning up on the move unless stopped at a signal on the way in?

 

[route101]

LNER do it aswell north of Stirling.

 

[Brissle Girl]

And me and of course then you had all the Rail Industry informed sources who said they wouldnt be able to get over the Devon Banks

Which is probably why the later order of the 802s have their engines higher rated to ensure that they can, as opposed to the 800s, which clearly would have had a problem given the change was made.

 

[Railperf]

And me and of course then you had all the Rail Industry informed sources who said they wouldnt be able to get over the Devon Banks

I was on a service with only 2/3 power struggling to reach 40mph on those gradients! Any slower we would have been going backwards Lol.
Scenic route but too slow!

 

[Prestige15]

Electric to diesel at 10:40
Diesel to electric at 20:20
Both of which while the train is in motion

 

[_toommm_]

Last week I saw a class 802 TP Arrive in Leeds with pan up coming from the York direction so they have been panning up on the move unless stopped at a signal on the way in?

They shouldn't be panning up at all West of York until Manchester Victoria. It's not worth it to run electric on the tiny bit between Neville Hill Depot and Holbeck Jn.

 

[Mintona]

They are usually started shortly before the traction changeover. They are switched off when running on electric.

It's a while since I've been on an 80x doing a traction change but IIRC, westbound Oxford fasts (not stopping at Didcot) would have the engines running between Goring and Cholsey for the switch to the non-wired avoiding lines at Didcot East Junction. Further west, trains to Bath and Bristol TM have the diesels running between Wootton Bassett and Christian Malford for where the wires run out east of Chippenham.

There is actually no requirement to start the engines before the switch from electric. They will often be started at the same point at which the pan is dropped. However some drivers do switch them on a few minutes earlier to get them running and make sure they start without problems.

 

[MotCO]

There is actually no requirement to start the engines before the switch from electric. They will often be started at the same point at which the pan is dropped. However some drivers do switch them on a few minutes earlier to get them running and make sure they start without problems.

Presumably there is a bit of a lag before the diesel engine is up to speed, so will the train coast for a bit?

 

[route101]

Do they ever run on diesel from London Paddington?

 

[pdeaves]

Presumably there is a bit of a lag before the diesel engine is up to speed, so will the train coast for a bit?

Measured in low numbers of seconds, I believe. Nothing significant.