Engine rpms in DMUS

Discussion in 'Traction & Rolling Stock' started by notadriver, 21 Jul 2019.

  1. notadriver

    notadriver Established Member

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    Does anyone know what the engine rpms were at top speed in the following units.

    First gen DMU with 4 speed transmission (70 mph)

    Class 150 / 156 sprinter / super sprinter.
    (75 mph)

    Class 158 (90 mph)

    Class 168/170 (100 mph)

    Class 185 (100 mph)

    Class 180 (125 mph)

    Many thanks.
     
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  3. driver9000

    driver9000 Established Member

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    As I remember 14x and 15x units are 2,100rpm.
     
  4. hexagon789

    hexagon789 Established Member

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    First Gen mechanical DMU - 1,800rpm for those with the 150hp engines, not sure about the other engine types.

    15x Sprinters are 2,100rpm

    158 are 2,100 with the Cummins and Perkins 350hp engines but 1,900rpm with the Cummins 400hp ones.

    168/170 are 1,900rpm

    185 and 180 are both 2,100rpm
     
  5. notadriver

    notadriver Established Member

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    Thanks to you both. I’m wondering if when the transmission goes into ‘direct drive’ or the last gear whether the full rpms is needed at max service speed?
     
  6. hexagon789

    hexagon789 Established Member

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    Yes, at full revs the train should be at max speed more-or-less. In a first-gen DMU, at 1,800rpm in 4th gear train speed will be approximately 65.5mph.
     
  7. 37057

    37057 Member

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    I've had a 185 engine at 2100 RPM but that was sat in the depot with a laptop plugged into the CCU.

    I've found an entry for a 185 doing 100 MPH with the Power-Brake Controller in 100% (CCU drive at 100% also) and 51 car at 1996 RPM, 53 car at 1983 RPM and 54 car at 1916 RPM. I would guess and say that wheel diameter is a major variant in these figures, however this is only a snapshot and these figures can vary by the second.

    There is also an entry logged for overspeed too at 102.6 MPH with 2033 RPM being the highest before being shut off automatically.

    A quick search of recent overspeeds across the fleet shows the highest being 2087 RPM, so it appears 100 MPH and below, these units don't actually hit the quoted figure.

    These transmission's "direct drive" are fluid couplings on 2nd and 3rd stages.
     
    Last edited: 21 Jul 2019
  8. hexagon789

    hexagon789 Established Member

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    I know it will vary unit to unit, but for 185s 2100 was the figure I had for them.

    Presumably then 2100 is the absolute maximum the engines will run at but to attain the rated 100 mph doesn't require the maximum engine speed giving a certain amount of leeway as it were.
     
  9. ash39

    ash39 Established Member

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    2100rpm will most likely be where the fuel cut off kicks in.

    If it's anything like an automotive engine, max power is usually achieved just short of max rpm.
     
  10. 37057

    37057 Member

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    2450 RPM is the limit for the QSK19 and that's when the 'Fuel Shut Off Valve' would de-energise, there would have to be something dangerously wrong if it were to reach this speed.
     
  11. ash39

    ash39 Established Member

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    I imagine the sound would be pretty spectacular!
     
  12. Ben Bow

    Ben Bow Member

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    Short video on Youtube showing a bench test on a QSK19 (180/185/Voyager/Meridian), quite interesting:

     
  13. hexagon789

    hexagon789 Established Member

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    Driver trying to emulate an HST? ;):lol:
     
  14. hooverboy

    hooverboy Member

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    for sprinters I think the torque convertor shifts at about 40mph.
     
  15. hooverboy

    hooverboy Member

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    as with most engines, maximum efficiency is between 60-70% of full rpm.
     
  16. hexagon789

    hexagon789 Established Member

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    Varies depending on a number of factors, but under full power the change to the fluid coupling is typically at 45mph in 75mph Sprinters.
     
  17. superkev

    superkev Established Member

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    Slightly off topic but there seems to be a few 185 experts here but my question is:-
    Has the hydro(something) retarder built into the 3 speed 185 Voith transmission been disabled. I seem to remember it had some initial problems?
    Thanks
    K
     
  18. 37057

    37057 Member

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    They're all working providing the engine is running. Occasionally they may get isolated temporarily to combat overheating in the summer but that's rare.
     
  19. hexagon789

    hexagon789 Established Member

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    They are in use, though occasionally don't know how long after the initial issues it took for them to be sorted to be more reliable level. If you look up Don Coffey on YouTube you'll find a number of 185 driver's eye views and you can hear the retarders in a couple of them.
     
  20. superkev

    superkev Established Member

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    Thanks to all
    K
     
  21. notadriver

    notadriver Established Member

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    Thanks for all your great replies.
     
  22. Llama

    Llama Member

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    Correct, anything changing up from torque converter to fluid coupling at 40mph or below with full traction power applied and I book it as a fault.
    158s (all engines) change up to fluid coupling at about 55mph under full power.
     
  23. hexagon789

    hexagon789 Established Member

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    Though can't Sprinters change-up under 40 in lower power settings?
     
  24. Llama

    Llama Member

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    Yes, about 30mph in 150-156 units in power notches 1-3, then incrementally 3-4 mph higher through the notches up to ~45mph in notch 7.
     
  25. hexagon789

    hexagon789 Established Member

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    Thank you, I thought I'd read that was the case somewhere.
     
  26. superkev

    superkev Established Member

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    Thinking about my earlier post re the 185 retarders dont the less reliable 180s have the same engine and power train.
    K
     
  27. hexagon789

    hexagon789 Established Member

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    Yes, same engines and same basic transmission but set up for 125mph so presumably different change-up speeds etc
     
  28. superkev

    superkev Established Member

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    Thanks. I wonder why the 180s particularly the Hull trains ones seem to feature so much in failure reports.
    K
     
  29. hwl

    hwl Established Member

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    Different final drive gearbox ratios
     
  30. 37057

    37057 Member

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    I've said this before in another thread and clearly got ignored!
     
  31. hwl

    hwl Established Member

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    I know the feeling!:rolleyes:
     

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