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

[DelW]

Good to see the explicit statement from the Mark Hopwood interview in Modern Railways about exactly where they’ll use third rail, the main change being that it will be used Aldershot junction to Guildford station (platform change) eastbound, and Shalford Jn to Aldershot Jn westbound.

IIRC at one stage it was authoritatively posted that the middle of the route in the Guildford area would not see DC power used at all.

That implies that the DC to diesel switch westbound at Aldershot South Junction will be made on the move. Presumably if that proves sufficiently reliable, then at some point in the future the eastbound changeover might be moved to Shalford Junction, which would eliminate diesel running through Guildford station and tunnels (apart from the two per day XCs).

Though I assume that the DC to diesel switch is inherently less reliable than vice versa. Is the short length of third rail east of the junction at Shalford enough to get a 769 clear of the Direct in the event that there was a problem with the changeover?

Even the current plans will reduce diesel running at Guildford by over 50% though, which is undoubtedly a benefit of these units.

 

[AM9]

That would be this video?

Excellent video. One thing that really surprised me was the shocking state of the slow lines at Salfords. Before anybody says it, yes I know that long telephoto lens's make most track look wobbly, but from 06:00 to 06:20 where the 769 enters Salford platforms the train is lurching quite violently at each of the kinks, especially the one it hits at 06:16.

For early days (at anything like real world running), the bugs seem to be fading away on the 769s. The next hurdle will be leaf fall time, but any time they are running instead of pure diesels is a change in the right direction.

 

[JN114]

IIRC at one stage it was authoritatively posted that the middle of the route in the Guildford area would not see DC power used at all.

I will hold my hands up to this one - we were originally told all power changes would be at a stand, which I’ve then regurgitated for discussions here. However I have since been put right - AC to Diesel/DC changeovers and vice versa still have to be done with DDS in neutral as was on a 319; however Diesel and DC can be used fully interchangeably (as Diesel is effectively DC)

Apologies for misleading members.

 

[swt_passenger]

I will hold my hands up to this one - we were originally told all power changes would be at a stand, which I’ve then regurgitated for discussions here. However I have since been put right - AC to Diesel/DC changeovers and vice versa still have to be done with DDS in neutral as was on a 319; however Diesel and DC can be used fully interchangeably (as Diesel is effectively DC)

Apologies for misleading members.

I don’t think you need to apologise. We can only go by what info is available at the time, but in the vast majority of cases info from TOC or NR employees is the best we get…


It will be interesting to see if they ever put the pan up on the short ECS move on or off the depot, although it would at least provide regular checks of the AC equipment, and practice for drivers...

 

[reddragon]

I will hold my hands up to this one - we were originally told all power changes would be at a stand, which I’ve then regurgitated for discussions here. However I have since been put right - AC to Diesel/DC changeovers and vice versa still have to be done with DDS in neutral as was on a 319; however Diesel and DC can be used fully interchangeably (as Diesel is effectively DC)

Apologies for misleading members.

That's fine. We all have to remember that these are a first of a type and we all would have based our views on the standard 319/769 set up not the unique GWR 769 variant.

 

[JonathanH]

That implies that the DC to diesel switch westbound at Aldershot South Junction will be made on the move.

Kind of comes back to the question I posed a few months ago about whether North Camp is effectively within range of 'coasting' with momentum from Aldershot South Junction. I can't quite recall where power is disapplied on a Turbo approaching North Camp. I suspect it is too far given the slowing to 40mph at Ash Junction and the occasional slowing for the level crossing barriers at Ash.

 

[adc82140]

I presume that diesel to DC and vice versa is easier because the diesel genset is effectively imitating the DC supply, whereas AC to DC (and therefore diesel) is much more involved?

 

[JN114]

It will be interesting to see if they ever put the pan up on the short ECS move on or off the depot, although it would at least provide regular checks of the AC equipment, and practice for drivers...

They almost certainly will use AC to get on/off depot, there are noise abatement restrictions which make depot operations for Turbos awkward. Being able to use AC negates all those.

 

[big all]

Kind of comes back to the question I posed a few months ago about whether North Camp is effectively within range of 'coasting' with momentum from Aldershot South Junction. I can't quite recall where power is disapplied on a Turbo approaching North Camp. I suspect it is too far given the slowing to 40mph at Ash Junction and the occasional slowing for the level crossing barriers at Ash.

yes easily
from memory on a stopper [pre 94]cross the canal just before the junction about 30-35 mph and coast you loose perhaps 7 or 8mph on the gentle grade but you keep to time ??

 

[swt_passenger]

They almost certainly will use AC to get on/off depot, there are noise abatement restrictions which make depot operations for Turbos awkward. Being able to use AC negates all those.

Ah yes of course, there’s been a bit of a long term campaign against Diesel engines along there since the massive depot changes .

 

[FenMan]

Out of interest, are the current timetables, which (we are told) have been built around 769 operation, predicated on DC or diesel power being used between Guildford - Aldershot South junction?

 

[fgwrich]

I don’t think you need to apologise. We can only go by what info is available at the time, but in the vast majority of cases info from TOC or NR employees is the best we get…


It will be interesting to see if they ever put the pan up on the short ECS move on or off the depot, although it would at least provide regular checks of the AC equipment, and practice for drivers...

I wonder how the Basingstoke branch will be treated - electric Reading to Reading West then diesel onwards, or Diesel all the way?

 

[Nicholas Lewis]

After all the delay its great to see this project finally begin to deliver the vision of Porterbrook and the NDL is excellent route to deploy them on as long as they don't use it as an excuse to slow the service down as per the test train timings last week. The fact it will be able to change over over on the move is excellent news and quite frankly anything new thats Bi Mode or multi voltage must have this built in.

Even if they get no more orders from passenger operators/govt we need to be building more BiMode units in future as that's quickest way to decarbonise the railway and as electrification progresses just remove the engines.

 

[FGW_DID]

I don’t think you need to apologise. We can only go by what info is available at the time, but in the vast majority of cases info from TOC or NR employees is the best we get…


It will be interesting to see if they ever put the pan up on the short ECS move on or off the depot, although it would at least provide regular checks of the AC equipment, and practice for drivers...

AC will be the default mode for all internal depot moves and on / off depot.

 

[andreading]

I wonder how the Basingstoke branch will be treated - electric Reading to Reading West then diesel onwards, or Diesel all the way?

Electrify to Reading Green Park? No structures in the way.

 

[SteelWeelApeal]

I wonder how the Basingstoke branch will be treated - electric Reading to Reading West then diesel onwards, or Diesel all the way?

As they tend to sit in Reading for a while, I’m hoping they will switch.

 

[43102EMR]

As they tend to sit in Reading for a while, I’m hoping they will switch.

My guess is it will be a similar situation to the GA 755s in which they’ll use overheads/third rail where possible if there are long dwell times, if the testing of the units is anything to go by.

 

[Fincra5]

Environmentally it makes sense for them to sit at Reading on AC, if there are there for a while. Really it depends how quick the switch is from GenSets to AC

As they tend to sit in Reading for a while, I’m hoping they will switch.

 

[FenMan]

Environmentally it makes sense for them to sit at Reading on AC, if there are there for a while. Really it depends how quick the switch is from GenSets to AC

It could be a struggle for the 769s to sit at Reading on AC when they will be mainly berthed on platforms 4-6, which are DC.

 

[swt_passenger]

It could be a struggle for the 769s to sit at Reading on AC when they will be mainly berthed on platforms 4-6, which are DC.

This part of the discussion (from post #946) is about the prospective Basingstoke service...

 

[FenMan]

This part of the discussion (from post #946) is about the prospective Basingstoke service...

Something for the Speculative Ideas sub-forum then.

 

[swt_passenger]

Something for the Speculative Ideas sub-forum then.

Not really, it has always been intended to use them on the Basingstoke service as well as North Downs.

 

[FenMan]

Not really, it has always been intended to use them on the Basingstoke service as well as North Downs.

Fair enough.

 

[Fincra5]

It could be a struggle for the 769s to sit at Reading on AC when they will be mainly berthed on platforms 4-6, which are DC.

Yes sorry, my comment was in relation to the Basingstoke Services and the NDL ones

 

[Mike Buckner]

I joined an on-line meeting/discussion with Mark Hopwood earlier this week and asked him about the 769s on the NDL.
.... On the matter of the passenger experience, he said that the trains are air-cooled (not air conditioned)

I would be grateful for enlightenment on the difference between air-cooled and air conditioned.

 

[Clarence Yard]

Air cooling generally takes air from outside the vehicle and cools or heats it where as air conditioning generally recirculates the air from inside the vehicle and cools or heats it.

 

[WAO]

Air conditioning requires refrigeration; the air being passed over the refrigerant evaporator which absorbs heat from the air. Refrigeration is heavy and requires power for the compressor, a problem for a dmu.

Air cooling is only ventilation; cooling being provided partly because outside air is usually cooler than cabin air and partly because moving or blown air has a higher convection coefficient than still air.

WAO

 

[Meerkat]

I thought the only difference was that cooling just cooled the air, whereas conditioning took the current air and filtered, cooled, and dehumidifier it?

 

[skyhigh]

I thought the only difference was that cooling just cooled the air, whereas conditioning took the current air and filtered, cooled, and dehumidifier it?

That was my understanding -

Air cooling is only ventilation; cooling being provided partly because outside air is usually cooler than cabin air and partly because moving or blown air has a higher convection coefficient than still air.

Isn't that just forced air ventilation? I thought air cooling still required refrigeration?

 

[AM9]

That was my understanding -

Isn't that just forced air ventilation? I thought air cooling still required refrigeration?

If the air being brought into the driver's cab is cooler than the normal ambient air there then the cab air is being cooled. In virtuallly all instances that I can think of, the air being drawn into a properly sited ventilation system on a train will be cooler than that already inside the train.