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

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

  1. Greybeard33

    Greybeard33 Established Member

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    It is perhaps worth quoting again what the Rail Engineer article last September had to say about the relative performance of the 769 and 150, according to Wabtec modelling:
    The proof of the proverbial pudding will, of course, be in the eating... assuming the 769 dish at long last lands on the TOCs' tables!
     
  2. Llama

    Llama Member

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    That claim of "higher tractive effort" starting away compared to a 150 - the figures just don't stack up.
     
  3. LNW-GW Joint

    LNW-GW Joint Veteran Member

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    Which makes it all the more frustrating that they don't seem to be getting any testing on the main line.
     
  4. themiller

    themiller Member

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    How much testing on the main line do they need? Given that they aren’t new units and have been well proved on 25kv, they only need to prove themselves under diesel power which I would have thought they are doing on the GCR. They don’t need to do endurance testing at 100 mph but lots of stop, accelerate, stop which is likely to be more of a guide to whether they can perform to what is needed on their intended routes.
     
  5. LNW-GW Joint

    LNW-GW Joint Veteran Member

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    By "main line testing" I mean anywhere on NR metals that is relevant to their intended usage.
    Preferably with a few hills and, as you say, frequent stops.
    The efficient changeover between diesel and electric is also pretty key to their operation, which they are not going to get on the GCR.
     
  6. a_c_skinner

    a_c_skinner Member

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    Are they doing that? Are they actually running there? It isn't a private location and I'd have thought a forum member from the area would have reported on any progress.
     
  7. LowLevel

    LowLevel Established Member

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    They run up and down frequently in Leicestershire.
     
  8. hwl

    hwl Established Member

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    Given the inefficiency of the hydraulic transmissions at low speeds it almost certainly does. Remember an electric motor has maximum torque at 0 rpm
     
  9. Llama

    Llama Member

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    So why are 319s so much slower starting away than 15x units?
     
  10. Charlie Smythe

    Charlie Smythe On Moderation

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    The 319s have less weight on driven wheels. So for a four car Class 150, 50% or around 77 tonnes is on the driven axles.

    Where all all traction equipment on a 319 is in the Motor Standard Open which weighs 50 tonnes. A class 319 weighs 140 tonnes. (50 / 140) x 100 is 35%. This deficit will only increase as the MAN engines and all other additional equipment being added to the 319 to covert them to 769’s will at 7.5 tonnes per driving trailer so 15 tonnes per train. This 15 tonnes does not contribute to adhesion.

    With this additional weight the percentage of weight on driven axles will be down to 32%.

    That is my best guess at answering your question.
     
    Last edited by a moderator: 29 Jan 2019
  11. a_c_skinner

    a_c_skinner Member

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    Is that a one liner I don't get or are they actually piling on the miles in modest seclusion? Sorry to be thick.
     
  12. Beemax

    Beemax Member

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    You mean the Great Central Heritage railway, where they'll be sharing track space with the fish and chip steam train?
     
  13. a_c_skinner

    a_c_skinner Member

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    They won't. Testing at higher speeds needs sole occupation of the line and all public access closed.
     
  14. LowLevel

    LowLevel Established Member

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    They are generally pottering about as required. They run at normal speeds with other traffic as required and at enhanced speeds as requested by the project engineers.

    If you go on YouTube there are videos of a unit passing Quorn station at 75 mph.

    Not all of the work being done requires the unit to move at all let alone at high speed.

    I can't give you any more info because it's a commercial project but it's easy to see the trains moving on a regular basis from public vantage points - there are two units there at present.
     
  15. Greybeard33

    Greybeard33 Established Member

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    So does a hydraulic torque converter - hence its name. And the hydraulic transmission also includes a gearbox, which further multiplies the engine torque when in low gear.
     
  16. Richard Scott

    Richard Scott Member

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    As far as efficiency goes I suspect the Electric transmission wins at low speed - large amounts of slip in the torque converter will generate a reasonable amount of heat and the gearbox will further reduce efficiency. The electric transmission is around 80% efficient (may be a little less at low speed due to higher currents and hence larger heating losses) but doubt a torque converter and gearbox approach that at the lower speeds. Happy to be proved wrong if someone has better information than I do.
     
  17. edwin_m

    edwin_m Veteran Member

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    However with the hydraulic transmission the engine is directly coupled at higher speeds, and while this may improve the transmission efficiency it may also mean the engine is running at a less efficient speed.
     
  18. Billy A

    Billy A Member

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    Not quite though. In second and third speeds the torque converter is replaced by fluid couplings (same basic idea but with one element less). Slip is a lot less but drive is still transmitted hydraulically. If I recall the efficiency is something over 90%.
     
  19. Richard Scott

    Richard Scott Member

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    So at higher speeds the two are fairly evenly matched, if the fluid coupling is 90% efficient, or thereabouts, then taking into account losses in the final drive it's probably very close to the efficiency of the electric transmission?
     
  20. Billy A

    Billy A Member

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    Very likely. Bear in mind that you're not going to find electric drive in your car except in the context of hybridisation because (amongst other things) it's less efficient. Hybrids use electric drive only at certain speeds.
     
  21. Llama

    Llama Member

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    There is clearly more to this
    There is less adhesive weight on a 319 than the equivalent 4 car 150 rake, but with a good rail when neither the 319 nor the 150 slip under traction power the amount of adhesive weight shouldn't be much of a factor.
     
  22. Charlie Smythe

    Charlie Smythe On Moderation

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    I know that neither of them slip under acceleration but it is something to consider.
     
  23. supervc-10

    supervc-10 Member

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    Kind of. Toyota's hybrid system is constantly using electrical power- it uses a planetary gearset with different components of that planetary gearset connected to different sections of the drivetrain, with the petrol engine, 2 electric motors, and of course the drive to the wheels. Meanwhile many other hybrid systems (for example Hyundai's or VW Group's) incorporate a single electric motor into the output of a relatively conventional dual-clutch 'automatic' gearbox. Things like the Golf GTE or the plug-in hybrid version of the Hyundai Ioniq can run at really quite high speeds on electricity only- up above 80mph IIRC.

    The closest to a 'diesel-electric' locomotive is the system used in the BMW i3 REX, which has a small scooter motor under the boot floor, which is not mechanically connected to the wheels, or the Chevrolet Volt/Vauxhall Ampera, which has a petrol motor which only drives the wheels directly under certain conditions- when the battery is low (or charge is being 'held' for later city driving) and the vehicle is at relatively high speed (IIRC it's about 40 mph and up).

    The big advantage an electric drive system has in a car is the regenerative braking. This is how a non-plug-in hybrid version of a car gets much better MPG than the equivalent petrol-only version. For example, going on figures from Toyota's website, the Auris 1.2 petrol gets 55.8 mpg combined, while the hybrid Auris, which is quicker, gets 68.8 mpg.

    Trains don't have the same stop/start problems as a car does. I doubt that the 769s will get as good an MPG as the same engines would get hauling a unit of the same weight but with a mechanical/torque converter drive (say, a re-engined doubled-up 150). The benefit comes from being able to run on electricity while under the wires, and I wouldn't be surprised if the more modern diesels are a bit better on fuel anyway compared to the elderly lumps under a Sprinter!
     
  24. samuelmorris

    samuelmorris Established Member

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    Indeed it's that ability to run on electric that's important. My plug-in Prius achieves around 60mpg at 75mph when in regular hybrid mode as there's no regenerative braking to be had - not bad, but unexemplary and probably easily matched by a regular diesel. On regular roads where regenerative braking is used it comes up to around 70, but in practice I regularly achieve 90+ due to having 30 or so miles of electric range to use each time I leave home / a charging facility. Where there is electrical infrastructure available, it absolutely makes sense to use it, even if it means carrying extra weight in areas where it can't be used.
     
  25. JohnMcL7

    JohnMcL7 Member

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    I saw a couple of pictures of 37884 hauling 769424 on a Brush-Allerton move, anyone know what that's for?
     
  26. 59CosG95

    59CosG95 Established Member

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    Crew familiarisation perhaps? Or more hopefully still, their actual entry into service?
     
  27. adsteamfan

    adsteamfan Member

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  28. td97

    td97 Member

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    Not mine but here's one I came across
    https://flic.kr/p/23Tqe2a
     
  29. jonesy3001

    jonesy3001 Established Member

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    went past crewe cams on time
     
  30. Peter Sarf

    Peter Sarf Established Member

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    Yes. What you describe is not even peculiar to the rail indistry. I have seen/endured it in other types of business. The "syndrome", if I may call it that, is more obvious/painful in the rail industry ONLY because it is in public view. Human nature is to defend by avoiding bad news. Although the truth is usually better it is naive to think that the truth is some kind of right.
     

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