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

[Roast Veg]

That surprises me given how slow off the mark a 165/166 is.

 

[reddragon]

The class 165/166 and class 769 should be assumed as roughly the same weight per coach

Class 769 = 1046hp - continuous efficiency = 85%
Class 166 = 1400hp - peak efficiency = 85% (higher speeds)

The class 769 would be quicker due to electric transmission on slower & stopping services, eg TV Branches / Wokingham - Redhill but the Class 166 will be quicker at higher non stop speeds - Reading - Wokingham / Redhill - Gatwick, just where there happens to be 3rd rail.

 

[JonathanH]

The class 769 would be quicker due to electric transmission on slower & stopping services, eg TV Branches / Wokingham - Redhill but the Class 166 will be quicker at higher non stop speeds - Reading - Wokingham / Redhill - Gatwick, just where there happens to be 3rd rail.

The stretches between Reigate and Dorking Deepdene, Dorking Deepdene and Guildford, Guildford and North Camp, North Camp and Blackwater and Blackwater and Wokingham are just as much 'non-stop' as Reading to Wokingham and Redhill to Gatwick Airport. Each will need acceleration. However, Redhill to Gatwick is the only bit of 'fast' route, the rest being no more than 70mph.

 

[fgwrich]

That surprises me given how slow off the mark a 165/166 is.

They aren't the best, thats for sure. Though a 165 is quicker due to the lack of the (useless) Air Conditioning system that the 166's retain. The Air Cooling takes less power. The worst offender is the perpetually slow 166201 - also known by many as Brian.

 

[northernbelle]

That surprises me given how slow off the mark a 165/166 is.

There's no doubt that BREL was trying to squeeze every last horse out of those Perkins engines. The truth is that the demand for creature comforts such as Air Conditioning was ahead of the curve in terms of being able to power it reliably with a suitably sized engine - same with the 158s. The proposed repower plan for the 'Turbo' units could be quite transformational in terms of the power available and their performance.

 

[43096]

There's no doubt that BREL was trying to squeeze every last horse out of those Perkins engines. The truth is that the demand for creature comforts such as Air Conditioning was ahead of the curve in terms of being able to power it reliably with a suitably sized engine - same with the 158s. The proposed repower plan for the 'Turbo' units could be quite transformational in terms of the power available and their performance.

What hasn't helped is the mandatory replacement of the original R22 refrigerant gas with R134a gas in the aircon systems. Unfortunately, although R134a is not ozone depleting (unlike R22), it is also less efficient in terms of heat transfer properties, so with a fixed size of system / limited power, the aircon is far more on the limit than it was ever designed for.

 

[Clarence Yard]

The original air con system fitted to the 166 units was made by Stones Iberica (a unique system) and wasn’t a great power draw on the units. That is not the case with the latest system.

The best accelerating Turbo units on the North Downs were the 165/0 units.

 

[northernbelle]

The original air con system fitted to the 166 units was made by Stones Iberica (a unique system) and wasn’t a great power draw on the units. That is not the case with the latest system.

The best accelerating Turbo units on the North Downs were the 165/0 units.

Were they the lower geared sets?

 

[D6130]

Were they the lower geared sets?

Yes.....designed for the steeply-graded Chiltern Lines, but equally at home on the steeply-graded North Downs line.

 

[Bikeman78]

The class 165/166 and class 769 should be assumed as roughly the same weight per coach

Class 769 = 1046hp - continuous efficiency = 85%
Class 166 = 1400hp - peak efficiency = 85% (higher speeds)

The class 769 would be quicker due to electric transmission on slower & stopping services, eg TV Branches / Wokingham - Redhill but the Class 166 will be quicker at higher non stop speeds - Reading - Wokingham / Redhill - Gatwick, just where there happens to be 3rd rail.

I've travelled on 769s. There is nothing fast about their acceleration at any point. I think a class 205 DEMU would give them a good run for their money.

 

[superalbs]

They aren't the best, thats for sure. Though a 165 is quicker due to the lack of the (useless) Air Conditioning system that the 166's retain. The Air Cooling takes less power. The worst offender is the perpetually slow 166201 - also known by many as Brian.

Where did the name come from?

 

[JonathanH]

Where did the name come from?

Brian

Brian (Ambroise in the French version) is a cheerful, bashful and intelligent snail. He is one of the main characters of The Magic Roundabout. Brian is a very slow, but well-meaning snail, who is hyperactive and cheerful despite Dougal's usual insults. He is quite practical, sensible and...

the-magic-roundabout.fandom.com

Brian (Ambroise in the French version) is a cheerful, bashful and intelligent snail.

If a 166 is referred to as a snail, there might be some different names given to the 769s.

 

[superalbs]

Brian

Brian (Ambroise in the French version) is a cheerful, bashful and intelligent snail. He is one of the main characters of The Magic Roundabout. Brian is a very slow, but well-meaning snail, who is hyperactive and cheerful despite Dougal's usual insults. He is quite practical, sensible and...

the-magic-roundabout.fandom.com

If a 166 is referred to as a snail, there might be some different names given to the 769s.

Let's start with dead snail!

 

[D6130]

Where did the name come from?

Several episodes of "The Magic Roundabout" are available to watch on YouTube although, ironically, Brian the snail seems to be quite a nippy mover!

 

[FGW_DID]

It’s actually nothing to do with Brian the Snail and 201 being slow. It was given the name by one of the RPIs, it was her very first train worked as an RPI and the Driver just happened to be called Brian. The name just stuck.

 

[Greybeard33]

I've travelled on 769s. There is nothing fast about their acceleration at any point. I think a class 205 DEMU would give them a good run for their money.

Remember the GWR 769s have aircon air cooling. The power that abstracts from the gensets will presumably make them even more sluggish than the TfW and Northern examples.

 

[Bikeman78]

Remember the GWR 769s have aircon. The power that abstracts from the gensets will presumably make them even more sluggish than the TfW and Northern examples.

Oh wow. Doesn't bear thinking about. I shall be out and about next week so I'll have another go on a 769 (if any are out) and do some more timings.

 

[JonathanH]

Remember the GWR 769s have aircon. The power that abstracts from the gensets will presumably make them even more sluggish than the TfW and Northern examples.

Isn't is air cooling like the 165s rather than air conditioning?

 

[big all]

I've travelled on 769s. There is nothing fast about their acceleration at any point. I think a class 205 DEMU would give them a good run for their money.

you will soon know
with a tadpole leaving dorking town you would hit 42-46mph [approx] by welcome bridge at the top??

 

[Greybeard33]

Isn't is air cooling like the 165s rather than air conditioning?

Air cooling, yes, but it still needs power.

 

[AM9]

Air cooling, yes, but it still needs power.

Peanuts compared with the traction demand.

 

[Greybeard33]

Peanuts compared with the traction demand.

I recall reading that the GWR 769s are equipped with solid state Auxiliary Power Supply units in place of the 319 Motor Alternator sets, because of the increased auxiliary power demand for air cooling.

 

[II]

Do we have any updates on Class 769s being able to use the 3rd rail on any of the three short(ish) sections between Reading and Gatwick? The middle one (Guildford to Ash) would be little use anyway, but it would be a positive to be able to use the juice between Reading<>Wokingham and Reigate/Redhill<>Gatwick.

 

[DelW]

Do we have any updates on Class 769s being able to use the 3rd rail on any of the three short(ish) sections between Reading and Gatwick? The middle one (Guildford to Ash) would be little use anyway, but it would be a positive to be able to use the juice between Reading<>Wokingham and Reigate/Redhill<>Gatwick.

There would be an advantage from the middle section too, in that it would eliminate diesel operations from Guildford station (other than the XC Voyagers at either end of the day, and occasional infrastructure or freight services).

It doesn't matter that much at present, though idling Turbos are both noisy and smelly, but it'll be more an issue if the plan to roof over the station and build above it ever goes ahead. (Though with luck, the likely post-Covid downturn in the office market, and more availability of areas for residential use in town centres, will have consigned that scheme to the bin.)

 

[JonathanH]

There would be an advantage from the middle section too, in that it would eliminate diesel operations from Guildford station (other than the XC Voyagers at either end of the day, and occasional infrastructure or freight services).

It only works for trains that stop at Guildford and Ash though.

I doubt coasting from Shalford Junction to Shalford or Aldershot South Junction to North Camp is going to work. As a genuine question, would this work technically at all?

It does seem that extension of electrification to North Camp and Shalford using existing grid supplies would be a good step even if the whole line can't be done. Is that technically feasible?

Maybe I need to start a speculative ideas thread.

https://www.railforums.co.uk/threads/third-rail-or-coasting-from-an-electrified-junction-to-the-next-station.215570/

 

[AM9]

I recall reading that the GWR 769s are equipped with solid state Auxiliary Power Supply units in place of the 319 Motor Alternator sets, because of the increased auxiliary power demand for air cooling.

The total load on the MA sets is tiny compared to the traction current from the 750VDC. The SS inverter would be more reliable and more efficient, as well as probably much lower mass.

 

[FGW_DID]

Any testing today?

Reported elsewhere as deferred to Monday. No paths yet shown.

Providing 2 out of the 3 769s don‘t spontaneously combust or anything crazy like that, then one should be out Monday 29th & Wednesday 31st. I don’t know any other timings apart from around 11.30 off Reading TCD. Again route not known at this time but likely to include a run to Didcot.

As per usual……………watch this space!

 

[Senna1210]

The 7699s have a APS Unit instead of the MA the AC works off the APS not the traction supply

 

[DelW]

It only works for trains that stop at Guildford and Ash though.

I doubt coasting from Shalford Junction to Shalford or Aldershot South Junction to North Camp is going to work. As a genuine question, would this work technically at all?

It does seem that extension of electrification to North Camp and Shalford using existing grid supplies would be a good step even if the whole line can't be done. Is that technically feasible?

Maybe I need to start a speculative ideas thread.

https://www.railforums.co.uk/threads/third-rail-or-coasting-from-an-electrified-junction-to-the-next-station.215570/

Well, everything stops at Guildford!

It's true that to get the full benefits would need units that could switch between diesel and third rail on the fly, which it seems like the 769s won't be able to do. That's assuming they do eventually appear on the North Downs, as with the reappearance of the 442s on the Direct we seem to be in "this year, next year, sometime, never" territory.

Electrifying to Shalford would provide for the Reading <> Guildford locals that lay over there, but wouldn't help with the intended two Gatwicks per hour which don't stop. That's if the 3tph timetable ever happens of course.

Incidentally, Guildford services have done badly from Covid cuts. Promised to go up to 4tph to Portsmouth and 3tph on the Downs, they have instead gone down 2tph and 1tph respectively. My doubt is whether the enhancements will ever happen now.

 

[JN114]

The 3tph N Downs service was run between Lockdowns in Autumn 2020; albeit off-peak only due to insufficient rolling stock to do it in peaks. It ran all day Saturdays though.