Porterbrook Cl.769 'Flex' trains from 319s, initially for Northern

[gallafent]

There’s plenty of opening windows, unless they choose to bolt them shut... Is modern AC really that unreliable? The problems seem to be mostly on older units like 158s.

They've bolted them shut on the 165s with air cooling. Don't worry though, they're still a bit loose so plenty of noise and cold draughts can get in (in my experience, which is of exactly two journeys only, and could have been the same unit, didn't notice).

 

[gallafent]

[…]whereas I have always had an issue with travelling in coaches with hopper windows open and a howling gale blowing through.

Absolutely agree … a 165 at 90mph with any of its windows open is deeply unpleasant, … worse than a 319/321 at 100mph (though I haven't been on one of those for years), not sure whether due to different size of hoppers etc., extra noise from diesel, … etc., ……… but yes, bolting them shut is definitely the correct approach.

Except of course for the actual correct approach, which was to replace them completely with windows without any opening at all, as Chiltern did when they refurbished theirs and added air cooling, about 15 years ago

 

[K.o.R]

Speak for yourself, I love units with opening windows. 313 in summer with a lovely breeze. Granted, not that great in winter although having the back ones open a fraction does help to deal with the condensation.

Sealing them completely shut is just great when the AC fails, or the train breaks down and loses aux power.

 

[a_c_skinner]

Do we know what is actually going on? Apart from not yet testing on the main line it seems to be going to plan (bit late, but going on). More vehicles arriving at Brush for conversion and so on. Are they still being driven up and down the GCR?

 

[507021]

According to a Facebook post, 769431 (Unit 3) is due next week.

 

[a_c_skinner]

So that is unit 3 finished? To GCR or the big railway?

 

[507021]

So that is unit 3 finished? To GCR or the big railway?

I would guess "moves north" means directly to Northern.

 

[Charlie Smythe]

The electric transmission will help somewhat versus a Sprinter, but only a bit more than 25% of the weight will be on powered axles rather than 50% for Sprinters and many modern EMUs. This may make them slow to accelerate at low speeds and (like the 319) prone to slip in poor adhesion. At higher speeds the power available will limit performance, which might be similar to a 150 but worse than a 319 on electric. As a 150 only goes up to 75mph the 769 may struggle to get much above that in diesel mode.


It doesn't work like that.

If you're thinking of AC motors, these require AC at a frequency that changes as the train accelerates. AC from the wire is at a constant frequency and AC drives convert it to DC before inverting it to produce the sort of AC the motors need. AC motors would save a bit of weight and might improve performance a bit, but would be a big cost as all the existing traction equipment would need replacing as well.

The "AC to DC Regulator" is no more than a bunch of diodes and pretty small compared to a diesel engine and a fuel tank. If you tried to drive an AC motor off a diesel engine without converting the power to DC and inverting it again, you'd have to synchronise the diesel with the motors rather like a mechanical transmission. Complete with some sort of clutch between the engine and the alternator, as the engine can't give power at zero speed to start the train.

So i have read that these units are four cars (well all knew that), but by reading you comment about weight on driven axles, it seems to me that these 4 traction motors will be on one car and the other three won't have driven axles, is this right? So does it go something like Car 1 + Engine, Car 2 = 4 traction motors, Car 3 = Engine, Car 4 trailing.

 

[a_c_skinner]

In the leaf fall season the plan is to lock all but the motor car OOU until there is enough weight in it.

Or put modern seats in the other three cars.

 

[edwin_m]

So i have read that these units are four cars (well all knew that), but by reading you comment about weight on driven axles, it seems to me that these 4 traction motors will be on one car and the other three won't have driven axles, is this right? So does it go something like Car 1 + Engine, Car 2 = 4 traction motors, Car 3 = Engine, Car 4 trailing.

Yes, except that the engines are in the two end cars. Car 2 also has the transformer and the electric traction electronics which probably makes it a bit heavier than the others in a 319, but I would think the engine outweighs this in the 769.

 

[MikePJ]

Charlie - the 319 follows the older model of EMU design of having a "motorcoach" (MSO) with the pantograph, traction electronics and all the traction motors (in this case 4). A 319 therefore has three unpowered coaches (two DTSOs and a TSO) and one motorcoach. The 769 conversion involves fitting the diesel engines to the two end coaches (DTSOs), but the traction motors remain on the motorcoach (MSO). So the extra weight of the diesel engines does not help provide extra adhesion because it's on unpowered axles, and in fact the marginal adhesion performance may even be worse because the motorcoach now has to push and pull the extra weight of the outer two coaches

 

[Charlie Smythe]

Charlie - the 319 follows the older model of EMU design of having a "motorcoach" (MSO) with the pantograph, traction electronics and all the traction motors (in this case 4). A 319 therefore has three unpowered coaches (two DTSOs and a TSO) and one motorcoach. The 769 conversion involves fitting the diesel engines to the two end coaches (DTSOs), but the traction motors remain on the motorcoach (MSO). So the extra weight of the diesel engines does not help provide extra adhesion because it's on unpowered axles, and in fact the marginal adhesion performance may even be worse because the motorcoach now has to push and pull the extra weight of the outer two coaches

Thanks for the explanation both Mike and Edwin. It can be quite confusing. So, does this mean that there may be issues in poor conditions and stops. Wheel slip etc.

 

[AM9]

Thanks for the explanation both Mike and Edwin. It can be quite confusing. So, does this mean that there may be issues in poor conditions and stops. Wheel slip etc.

What do you mean by "issues in poor conditions and stops?" If by stops you mean slowing and stopping, then the unit as a whole will be no worse than as an EMU as the additional inertia from the diesel generators sets mass also gives additional adhesion. By selecting the Class 319/4 sub-class for this programme, their 2006 modification to increase the emegency brake pressure to higher standard value of 12.5G would ensure adequate braking performance when needed, (see my post #2324 in this thread).

 

[Charlie Smythe]

What do you mean by "issues in poor conditions and stops?" If by stops you mean slowing and stopping, then the unit as a whole will be no worse than as an EMU as the additional inertia from the diesel generators sets mass also gives additional adhesion. By selecting the Class 319/4 sub-class for this programme, their 2006 modification to increase the emegency brake pressure to higher standard value of 12.5G would ensure adequate braking performance when needed, (see my post #2324 in this thread).

When i say stops i mean at stations and then having issues pulling away in poor conditions.

 

[59CosG95]

When i say stops i mean at stations and then having issues pulling away in poor conditions.

I think you mean "accelerating from a standing start" - trains don't always stop at stations!
Yes, they probably would be worse at accelerating than a 319.

 

[Mogster]

Apparently these are going to be used between Southport and Manchester.

There’s quite an uphill drag between Wigan and Lostock with a few stops. I’ve no idea what the gradient is but pulling away from Hindley and Westhoughton stations seems to regularly cause traction problems. Hopefully Wigan to Lostock is one of these worst case routes that they have in mind when testing these contraptions.

 

[childwallblues]

Apparently these are going to be used between Southport and Manchester.

There’s quite an uphill drag between Wigan and Lostock with a few stops. I’ve no idea what the gradient is but pulling away from Hindley and Westhoughton stations seems to regularly cause traction problems. Hopefully Wigan to Lostock is one of these worst case routes that they have in mind when testing these contraptions.

Unless things have changed recently they were going to be used between Wigan NW-Alerley Edge/Stalybridge which would require six units.

 

[anthony263]

What do you mean by "issues in poor conditions and stops?" If by stops you mean slowing and stopping, then the unit as a whole will be no worse than as an EMU as the additional inertia from the diesel generators sets mass also gives additional adhesion. By selecting the Class 319/4 sub-class for this programme, their 2006 modification to increase the emegency brake pressure to higher standard value of 12.5G would ensure adequate braking performance when needed, (see my post #2324 in this thread).

Dont forget the TFW 769s are being converted from the 319/0 sub class

 

[fgwrich]

What do you mean by "issues in poor conditions and stops?" If by stops you mean slowing and stopping, then the unit as a whole will be no worse than as an EMU as the additional inertia from the diesel generators sets mass also gives additional adhesion. By selecting the Class 319/4 sub-class for this programme, their 2006 modification to increase the emegency brake pressure to higher standard value of 12.5G would ensure adequate braking performance when needed, (see my post #2324 in this thread).

I certainly know that there is some concern by my colleagues over in GWR in Reading about how these will perform, more specifically on the North Downs line. There are already some restrictions on Turbos operating with 1? engine isolated due to the gradients along the route, so it will certainly be interesting to see how the 769s perform. At least, from what you've said about the /4 class, the braking should be better than initially thought.

 

[big all]

managed with around 105-115 tonne dmmus and demus and 600hp for long enough
the steepest grade is aldershot south juntion towards ash about 50-100yards at something like 1 in 49 with another steep approach to platforms at reading but appart from that the average is around 1in 95-125 in the next steeper sections like dorking bank
reduce power by about 30% you need around 5-10% more time which will often come within normal running time yes you work harder with less coasting but you get there if a wee bit late

 

[AM9]

I certainly know that there is some concern by my colleagues over in GWR in Reading about how these will perform, more specifically on the North Downs line. There are already some restrictions on Turbos operating with 1? engine isolated due to the gradients along the route, so it will certainly be interesting to see how the 769s perform. At least, from what you've said about the /4 class, the braking should be better than initially thought.

Although the 319s would have a 'less than lively' perfomance if only one engine was available, the electric transmission would allow all the power from the working engine to feed the four motors when pulling away. The adhesion would be the same, unlike a diesel hydraulic or mechanical unit which would only drive those axles connected to the working engine. Consider the 'Thumpers' with their single 600hp engine driving a generator feeding two motors. These units are still ocasionally used as tractor units to haul other EMUS.
Braking wise, the units have had 30 years of heavy use where braking from near 100 mph to standstill was part of normal service. ER retardation was the norm. ER will still be available when in diesel mode.

 

[big all]

Although the 319s would have a 'less than lively' perfomance if only one engine was available, the electric transmission would allow all the power from the working engine to feed the four motors when pulling away. The adhesion would be the same, unlike a diesel hydraulic or mechanical unit which would only drive those axles connected to the working engine. Consider the 'Thumpers' with their single 600hp engine driving a generator feeding two motors. These units are still ocasionally used as tractor units to haul other EMUS.
Braking wise, the units have had 30 years of heavy use where braking from near 100 mph to standstill was part of normal service. ER retardation was the norm. ER will still be available when in diesel mode.

going from redhill to reading with an engine out on a dmmu was never a problem a good unit you wouldnt really notice on a slow or a fast yes a bit more work to very hard work but not a problem normal shedules possible with little late running
you would never normally go with 2 out or 50% power but you would on the last or iff already on route keep going yes up hill loosing masses off time [dorking bank pigs hill wanborough sandhurst ] but the time lost would be perhaps 25-40 mins which is a lot but compared to waiting for assistance and coupling to another dmmu at a location where no one in years has attached 2 together is far quicker to carry on than wait with the often possibility that the stalled powercar because the turning transmission would often charge the batteries enough on downhill to start an engine on the failed end and give an approaching normal run even if the final engine wont or is slow to pay ball

 

[deltic08]

In the leaf fall season the plan is to lock all but the motor car OOU until there is enough weight in it.

Or put modern seats in the other three cars.

No, the plan should be to cut down all the lineside forests throughout the country. They are a disgrace and in places are actually hit by passing trains.

 

[JN114]

There are already some restrictions on Turbos operating with 1? engine isolated due to the gradients along the route, so it will certainly be interesting to see how the 769s perform.

No specific restriction for engine out on the North Downs - but once an engine is out on a Turbo you lose all electrical power to the vehicle, there’s no cross-feed so you’ll lose headlights and taillights within a couple of hours if it’s a driving vehicle. A Turbo on only one engine will have an engine out on a driving vehicle so it will be one trip back to Reading and onto the depot for some magic spanner action.

 

[33021]

Charlie - the 319 follows the older model of EMU design of having a "motorcoach" (MSO) with the pantograph, traction electronics and all the traction motors (in this case 4). A 319 therefore has three unpowered coaches (two DTSOs and a TSO) and one motorcoach. The 769 conversion involves fitting the diesel engines to the two end coaches (DTSOs), but the traction motors remain on the motorcoach (MSO). So the extra weight of the diesel engines does not help provide extra adhesion because it's on unpowered axles, and in fact the marginal adhesion performance may even be worse because the motorcoach now has to push and pull the extra weight of the outer two coaches

It’s certainly one model of design but not necessarily ‘older’ as class 405/411/412/415/313/314/315/507/508 have their traction motors distributed on both driving vehicles and all pre-date 317/318/319/320/321/325 EMUs

 

[LOL The Irony]

It’s certainly one model of design but not necessarily ‘older’ as class 405/411/412/415/313/314/315/507/508 have their traction motors distributed on both driving vehicles and all pre-date 317/318/319/320/321/325 EMUs

The Mk3 EMU's were obviously a lazy design then.

 

[AM9]

The Mk3 EMU's were obviously a lazy design then.

Not so much lazy. The 'PEP' derivatives were primarily designed as suburban ('metro' in current parlance) units. Acceleration was a key part in the performance. The early Southern Region units (411-415) were just continuations of Southern Railway practice of putting the motor bogies at the leading and trailing ends of the unit where the collector shoes were. It reduced the through power cabling demands. The successor design to the class 411 & 2, (the Kent mainline 4-CEP/4BEP EMUs) were the CIGs and BIGs where the established ac practice of using the transformer/rectifier and switchgear mass to improve the adhesion meant that the unit operated traction-wise, much as a loco plus 3-car LHCS train.
This design practice continued through the MKIII era (except the class 455s which were like most previous SR DC suburban units) until power electronics made the distribution of traction controls under coaches much easier. So 'lazy' is not really an appropriate word to describe the design. If it wasn't broken, why fix it?

 

[Ken H]

The Mk3 EMU's were obviously a lazy design then.

cheap
development of the 312 electrically.
There were no AC motors then so big DC ones were the norm. Just moved on from tap changers to thyristors. Power electronics were in their infancy. And there were concerns about signalling interference.

 

[AM9]

cheap
development of the 312 electrically.
There were no AC motors then so big DC ones were the norm. Just moved on from tap changers to thyristors. Power electronics were in their infancy. And there were concerns about signalling interference.

They MKIII designs were created to replce ageing stock in a time when the government's attitude was to starve the railways. The APT was killed by the government so innovation was further stifled.
As you say, DC traction motors were large and heavy, so doubling the number on a 160 ton train was not an economic argument when paths weren't so crowded as they are now. Also running low voltage cabling the length of a train and providing remote electromechanical switchgear would be an extravagance just to get slightly better adhesion on a few days per year. What the MKIIIs did have though was good crash resistance and passenger protection. Witness the fact that they are still perfectly acceptable in today's safety concious environment.

 

[AMD]

Unless things have changed recently they were going to be used between Wigan NW-Alerley Edge/Stalybridge which would require six units.

Still the last known plan, as they can run under the wires for a large proportion of the circuit - the only bits on diesel power will be Wigan - Bolton & Victoria - Stalybridge.