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

Discussion in 'Traction & Rolling Stock' started by aformeruser, 2 Dec 2016.

  1. JonathanH

    JonathanH Established Member

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    Who says that GWR could afford new build stock on the North Downs Line, Reading to Basingstoke and the Thames Branches? I don't think it is obvious that they can. The cost of 769s only appears to be justified by being able to send 165s west to facilitate a cascade to release the 143s and the oddball 150s.
     
  2. Clarence Yard

    Clarence Yard Member

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    The 769 units were not justified on the basis of a cascade west. The justification had more to do with a certain project, in those far off optimistic days, that required the use of 387 units before Crossrail released them off their booked workings. The 769 units were to replace Turbos to cover the released 12 x 387 units.

    The 143 units were to be released by the (still incoming) HST GTi sets and when the Crossrail service released the Turbos that were covering the 387 workings, they were to go West to release up to 12 x 150 units to go North and/or stay to help run additional services.

    No TOC can afford new or additional stock. Whether a service or whole TOC is profitable or not is irrelevant as the DfT looks at the TOC as one financial entity, not by individual service group. So all the key decisions about rolling stock are ultimately political, authorised by the DfT. You can’t lease stock or alter an existing lease without their express permission.
     
  3. ed1971

    ed1971 Member

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    It would be interesting to know what the fuel consumption of the 769 is compared to other DMUs. I have read that a Pacer does around 10 MPG per carriage and a 150 around 5.5 MPG per carriage.
     
  4. childwallblues

    childwallblues Established Member

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    Will that be based at Allerton or Crewe?
     
  5. Grannyjoans

    Grannyjoans Member

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    Well the fuel tanks on the 142's only hold 800 litres while the fuel tanks on the 150/156 hold 1600 litres Per vehicle.
     
  6. AM9

    AM9 Established Member

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    Well, a 769 is only slightly heavier than 2 x 150, it has a much newer Euro IIIb pair of engines and a more energy efficient transmission. So they are both comparable when running as diesels. The 769s of course are much more energy efficient when operating from 25kV or even 3rd rail, plus their range is then effectively unlimited.
    It is better to consider their fuel consumption per seat and per passenger (when crush loaded).
     
  7. Grannyjoans

    Grannyjoans Member

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    I really don't understand how the 769 will beat the performance of a pair of 150's away from the wires.
    2x 523 horsepower engines (1,046hp) vs 4 x 285 horsepower engines (1,140hp) with less weight.
     
  8. Llama

    Llama Established Member

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    Plus the auxiliaries on the 769 - all heating is electric vs. waste engine heat as on the 150, the motor-alternator set and the compressor runs off the 750v busline on the 769 (vs being 4x much smaller items on the 150).
     
  9. Grannyjoans

    Grannyjoans Member

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    Plus all the power on the 769 is being put down by just 1 car out of 4.

    I can't help feeling some sort of new CAF bi mode unit based on the 331 would have been better.
     
  10. AM9

    AM9 Established Member

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    Because the 150s have hydraulic transmissions that are not as efficient as electric generator/motor transmissions. A diesel-electric can operate with its diesel engine running mostly at the most efficient speed. The generator can then take most of that power and run the DC motors at maximum torque and then power almost from standstill. Fluid torque converters are not that efficient at certain speeds, and diesel engines on units such as 150s cannot give their rated power for much of the time in service.
     
  11. big all

    big all On Moderation

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    an increase off 20 or 30 % weight will make perhaps 5-10% extra on timing
    with perhaps 10- 15% extra weight it will be less than half so perhaps 2-4% extra on timing because weight and drag are doubled with speed and a bit more
    electrical transmission will operate at perhaps 85-95% efficiency through the range where as an engine on variable revs on gearing will be perhaps 90-95% for 30% off the time when at or near gear change speed when maximum torque is developed
    it may be perhaps 80- 85% efficiency for another 30% off the time because its medium to high speed [revs] then a further say 40% off perhaps 75% efficient as its on low revs and low torque
    the actual percentages are pure guesses but illustrates why power weight and excceleration are an equation and not a direct comparison between mechanical and electrical transmission
     
  12. JN114

    JN114 Established Member

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    Because they’re apples and oranges.

    The engines on a 150 have to directly drive the train - there are multiple efficiency losses through the complex drive train to get that power to the wheel. The “engines” on a 769 are only being used to generate electricity. The drivetrain is much simpler and much much more efficient.

    The modelling has been done by Wabtec Faiveley and validated in the trial running on the GCR and the small amount on the Mainline thus far. The performance is comparable to a 150.
     
  13. tomuk

    tomuk Member

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    Diesel-Electric transmission isn't 100% efficient. In actual fact it is probably less efficient than a 172/195 with their six speed ecomat gearboxs. A 'normal' Sprinter with Voith hydraulic transmission is less efficient during acceleration but is quite good once changed into 'top' gear.
     
  14. 73001

    73001 Member

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    Nobody said it was 100% efficient. But as has already been stated it's comparable with a 150 in terms of on the track performance. The two systems are completely different; granted, there are probably better ways of getting from A to B than a 769 but they've got them now so let's see what they're like in traffic (eventually). This constant "mine is better than yours" does nothing for the thread content.
     
  15. AM9

    AM9 Established Member

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    Ultimately, all energy on either train comes from diesel engines. In the case of the 769s it is all via the two generators. The difference is that the diesel engines on the 769s are run at a sufficient speed to maintain the main bus at 750V. That speed can be at the most efficient (in terms of fuel vs power conversion or just maximum power) for however long is required, irrespective of the speed required at the wheel.
    For instance, the Cummins NT855R5 engines can produce 213kW at 2100 rpm. That is well up the speed range for a 14L diesel engine and because of the limitations of a torque hydraulic converter, will not produce the required torque that the power rating might suggest. When an electric transmission is used though, the engine can be run at it's most efficient level (e.g. kW/Ltr fuel/Hr.) and allowing for generator losses, virtually all of that power is available for the traction motors.
    The class 319 has DC motors with a total continuous rating of 990kW which is more than the two gensets can produce, so they do not limit train performance when it is running on diesel. Given their age, the lower stress levels should also increase their reliability above that experienced when they are driven under wires.
     
    Last edited: 23 Dec 2019
  16. a_c_skinner

    a_c_skinner Established Member

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    Not something that gets said on here often! Yes, things have moved on; more action needed on CO2 and pollutants in cities, demise of some electification projects and the end of prospects of other electrification. It is now plain that more bimodes would have been a better option. Liverpool, Manchester and Leeds and Newcastle all have the ability to run their services without diesel for a good proportion of the intra urban miles.
     
  17. AM9

    AM9 Established Member

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    Or even diesel-electric (DEMUs) which could form the basis for easy conversions. CAF even include them in their Civity range.
     
  18. Minstral25

    Minstral25 Established Member

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    Thank you for the detailed assessment. It seems to me that the North Downs line has potential to link up much of the South without crossing London from Ashford, Tonbridge. Maidstone, Redhill (Gatwick/Brighton), Guildford, Reading and Oxford. Whether electricfied or not and thus could benefit from new and better stock. Are the 769's still necessary and could they be replaced by newer stock with an aim to improve services significantly?
     
  19. AM9

    AM9 Established Member

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    Any service can have its trains replaced with better/newer/more expensive types so there would be a benefit provided thwe cost wasn't considered. Those using it would presumably be happier to travel in them. The question is, is there sufficient patronage in the North Downs line to justify the cost of new trains, as I doubt that passengers on other lines would be happy to put up with trains that were inadequate for their services just so that relatively few passengers could travel in luxury. Most trains are replaced for operational reasons, not to appease a few passengers.
     
  20. starlightEXPRESS

    starlightEXPRESS Member

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    Forgive my ignorance, but since TfL Rail have now taken over most of the Reading-Paddington stoppers, does that mean that the Class 769s are no longer required? What will happen to the Turbos that should have been covering the Class 378s?

    (Is the "certain project" that you mention the refurbishment of the 387s for Heathrow Express?)
     
  21. Greybeard33

    Greybeard33 Established Member

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    Well said. Hopefully it will not be too long now before we have some reports from Northern drivers of real world 769 performance on actual Northern routes. Perhaps we can wait until then, rather than yet again recycling inconclusive theoretical arguments built on assumptions.

    Unless anyone has any hard data for the comparative tractive effort versus speed of a 769 and a double 150?
     
  22. Grannyjoans

    Grannyjoans Member

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    One thing for sure, the 769 will be quieter and cleaner than a pair of 150's, even in diesel mode. Also the driving cab of the 769 will be an improvement over the 150 - many of which are in a derelict state and poorer ergonomically.
     
  23. Llama

    Llama Established Member

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    There's so much variation between performance of individual units that any traction effort info is meaningless.

    The average 150 on its own with an average, non-excessive load (say 30-50 passengers) might reach say 70-75 on the gentle rising gradient from Salford Crescent towards Bolton, assuming clear signals & no running brake test needed. Two 150s in multiple should reach 75, anything less and you know you've potentially got a dud one (or slightly dud pair). This doesn't include faults such as engines reverting to idle, which is usually obvious to an experienced driver.

    A poor 150 might manage 60-65 on the same stretch. A decent one will get to 75 no problem and once there run at that speed with only a partial traction power setting.

    Even a poor 319 will reach 75mph without breaking a sweat up to Bolton. However no 319 will reach 100mph, they're just not capable, 85-90mph is about all you can expect and that will take forever.

    By comparison a 331, even a 4-car, will reach 100mph on the same stretch very very quickly as soon as the line speed permits it (line speed is 95mph after Agecroft, 100mph 1/2 mile after Clifton). Even without taking full traction power and when heavily loaded a 331 will easily do 100mph on that route. The difference between those units and everything else Northern operate (even 323s) is monstrous.
     
  24. Grannyjoans

    Grannyjoans Member

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    331's really are just what has been needed for a long time.
    The sluggish 142's / 150's / 156's always struggled to reach line speed in too many places. Even 319's, to a lesser extent.
     
  25. trainmania100

    trainmania100 Established Member

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    Does anyone know how many 769s for GWR have been converted and when the driver training starts? I haven't been keeping up to date on this thread unfortunately,

    Last I heard they were training the managers
     
  26. PHILIPE

    PHILIPE Veteran Member

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  27. Clarence Yard

    Clarence Yard Member

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    No, they are still required as 14 diagrams worth of Turbos are required in the West, either to replace cl.150 or for use on additional services in the West that the DfT are contemplating buying as part of DA3. I can’t give any details out on those potential additional services.

    It is likely, on the latest Porterbrook “programme”, that the first 2 769 units won’t be with GWR much before April and it will be the summer before the rest start to arrive. Delivery is likely to stretch into 2021.
     
  28. Deepgreen

    Deepgreen Established Member

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    It will be interesting to see how the 769s cope with the North Downs route's notorious leaf fall problems - is their single motored coach expected to have any better tractive effort than the Turbos which they are purported to be replacing?
     
  29. AM9

    AM9 Established Member

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    Even with just one of the four cars motored and the additional weight of the gensets and fuel tanks on trailing cars, there is over 30% adhesion on a 769. Remember, the MOS weighs over 50 tonnes. Drivers on Thameslink learnt how to drive the 319s during the leafall months, which was essential to get them up to near linespeed to maintain precious headways on the MML.
     
  30. Grannyjoans

    Grannyjoans Member

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    With the arrival of all these 769 flexes, will we soon see the first 150 scrappings ?
     

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