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

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

  1. AM9

    AM9 Established Member

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    OK correct.

    Give or take 4 years, there were 4 EPBS in use up to 1995, many of the CEPS were from 1956 and all of them were MKI designs. That's a big difference compared to the 150s (14_15 yrs old), 153s 155s (11-12 yrs old), 153s (10-12yrs old) and the 150s (just 7-10 yrs old). So not even in the same era of train design. The reason that so much of the EMUS were replaced around the turn of the century was for safety issues such as slam doors and asbestos content. Most of those issues outside the south-east were dealt with by the '80s.
     
    Last edited: 11 Jan 2019
  2. Charlie Smythe

    Charlie Smythe On Moderation

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    No never mind, I meant to say don't. They don't add to adhesion. So the 7.5 tonne per driving trailer does not add to adhesion. So the 769 flex has 15 tonne more dead weight than a 319.
     
  3. Charlie Smythe

    Charlie Smythe On Moderation

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    A Class 769 Flex will have a mass of around 156 tonnes and have an engine output (not at the rail) of 1050hp. This gives a hp/t of 6.7.
    A 4 car Class 150 has a mass of 153 tonnes and has a engine output (not at the rail) of 1140hp.
    This gives a hp/t of 7.67.

    According to this article https://www.railengineer.uk/2018/09/27/bi-mode-good-tri-mode-better/ the 769 will put 550 kw to the rail which is around 740hp. I don't know the horse power at the rail figure for a Class 150 so i can't compare.

    This means that 70% of the 769's engine output is available at the rail with the rest being auxiliaries and efficiency losses.
     
  4. big all

    big all Member

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    as we know throught history you can take the same power unit used by several manufacturers and they will get quite different levels off performance
    as there are so many variables best to wait as time will tell although a newer engine design and transmission will tend to be nearer to 100% spec than an old all be it recently re-engineered engine and transmission unless modified to improve output and efficiency
     
  5. AM9

    AM9 Established Member

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    It's not just the amount of power available from the prime mover that ultimately matters. As has been discussed further up this thread in various posts, the main issues are:
    a) the power at the wheel at key points in the intended service duty
    b) the level of adhesion available with which to apply that power
    c) the impact of the load (passenger) on the adhesion and acceleration
    d) the durability of the traction in service​
    There are probably other issues but those are the main items for a passenger train, so:
    a) in the case of DMUs, and this discussion, it is manily determined by the design of the transmission. In the case of a conventional DMU, the transmission is usually a hydraulic torque converter which acts as a transformer between high input speed low torque, and low (including zero) output speed with maximum torque. In a diesel-electric transmission, all of the shaft power on the generator is fed to the generator as the engine can be run continuously at the speed in which peak output is available.This is then applied to the wheels to provide maximum torque from standstill. The engine can be operated at its optimum speed almost throughout the full speed range of the train.
    In practice, thetorque converter is extrememly inefficient when the input to output shaft speeds are furthest apart, i.e. on starting. For the diesel electric transmission, the full power available at the shaft can be used at the wheels
    b) for the adhesion calculations for the classes 319 and 769, see my post #2700. Here the difference between a 319 empty/loaded/crush loaded and a 769 similarly loaded are quite small. The performance ofa 319 when fully loaded is adequate for the most demanding service so it's use on even quite busy secondary lines in the North (or elsewhere) are not likely to provide too many surprises.
    c) unless a new maximum loading of crush load on a 769 (and then adding in say 15t for the gensets etc.) is required, there shouldn't be any issues when fully loaded.
    d) diesel-electric transmission has been in use since the beginning of diesel trains. It's deployment and maintenance is a known quantity and provided none of the new components have durability issues, (mainly the genset), the 769s should provide reasonable service and running costs, especially compared to a torque converter transmission.

    But as above, the key is to at what speeds the power is available and at what stress levels to the engine and transmission.
     
  6. big all

    big all Member

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    as an aside
    thumpers had 2 x250hp traction motors on the motor coach
    you now think 56tons means a good load on the motors for grip so 14tonnes on the driving axles ??
    well quite wrong the motor bogie are at the light end to spread the weight so perhaps a 20 tonne 10 ton axle load so a bit less an extra grip but aided by an extra bogie clearing contamination off the rails
     
  7. AM9

    AM9 Established Member

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    If I understand your post, I think that the motor bogies are at the opposite end to (partially) equalise the weight across the length of the vehicle, - especially as the thumpers were designed for branch lines where axle load and bridge limitations would be a consideration. Given that they were deployed as replacements for steam on line where traffic wasn't considered heavy enough to justify electrification, they were designed to be as gentle to the track as diesel technology of the day would allow. In addition, leaf railhead contamination wasn't as big an issue in steam days as lines were generally kept clear of vegetation to prevent fires, in drier periods.
     
  8. 317 forever

    317 forever Member

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  9. Mathew S

    Mathew S Member

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    Er, what Blackpool - Atherton - Hazel Grove services?
     
  10. Mogster

    Mogster Member

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    That’s a new one, I should find it quite handy :lol:
     
  11. 323235

    323235 Established Member

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    Via Atherton? First I've heard of this.
     
  12. samuelmorris

    samuelmorris Established Member

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    In diesel guise however, you wouldn't have the third-rail current limit to deal with. On AC power, Electrostars are considerably more powerful and even with a set of motors out would still have a similar amount of power to a 319.
     
  13. AM9

    AM9 Established Member

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    But Electrostars are both 24% heavier and have the additional load on the generator of air conditioning, - maybe another 80kW at times.
     
  14. samuelmorris

    samuelmorris Established Member

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    Indeed they are, performance will depend greatly on how powerful the engines are. Given the relatively restricted 20m length given all the extra equipment I can see them struggling to fit enough power unless they either turn them into battery units, or remove the pantograph and transformer and fit a thumper-esque upper level engine with a higher power output in its place. A diesel / third rail bi-mode could still be useful in certain areas, just nowhere near as many as diesel/overhead.
     
  15. 43096

    43096 Established Member

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    One of the reasons the 319s are better for this conversion is because the majority of the power equipment is on one vehicle, which leaves space under the two driving trailers for the engines. An Electrostar is a rather different beast, as three vehicles out of four have traction equipment including the converters etc., so I'd struggle to see how you would fit engines under them without some major surgery.
     
  16. Grannyjoans

    Grannyjoans Member

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    I thought this "plan" is out of date; the latest plan now are that the 323's are being returned to Porterbrook in favour of keeping the 319's!

    Or at least, that's what everything I've heard and read more recently is favouring, with the added clue that Northern are constantly repainting & refurbing 319's but not 323's.
     
  17. bb21

    bb21 Moderator Staff Member Moderator

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    Discussion on ROG 769's and Royal Mail use are now in this thread.
     

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