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Thread: J3A Hudson Steam Generation vs Usage

  1. #1
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    Default J3A Hudson Steam Generation vs Usage

    Has anyone modified the original eng files for the American Classic J3As? I've had the set since it first came out and find stream generation vs steam usage problems when using the AI Fireman. I don't have this problem with other steam locomotives.

    In anticipation of questions, the differential between generation and useage shrinks and eventually reverses even with conservative driving on generally level grade. Boiler pressure drops to 182 but no further. But speed maxes at around 60mph.

    Thanks,
    Barry

  2. #2
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    Default RE: J3A Hudson Steam Generation vs Usage

    I havent done the j3a files yet, but I had a wee go at the ese.eng which is the same engine. This also suffers from the same problems.

    File attached.

    Beer is not a matter of life and death. It is much more serious than that.
    mervyn.

  3. #3
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    Default RE: J3A Hudson Steam Generation vs Usage

    Baldwin:

    Many thanks. I'll give it a try in all 4 locomotives. Glad to hear from someone who has the same challenges with the T3As. All in all, though, given when they were created, these remain among my favorites MSTS locomotives. The whistle is worth the price of admission...

    Thanks again and I'll let you know how it works for me

  4. #4
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    Default RE: J3A Hudson Steam Generation vs Usage

    Mervyn,
    A quick glance at that .eng file revealed two things that would cause problems. First, the CoalBurnage() value had the units separated from the numeric value. Won't do: there must be no spaces between.
    Second, the MaxBoilerOutput() should always be at least 10% larger than the ExhaustLimit() to allow for non-cylinder uses of the steam.


  5. #5
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    Default RE: J3A Hudson Steam Generation vs Usage

    Bill:

    The file works like a charm. I've repeated a run from Washington to Philadelphia on NECv4 with the ESE and Mervyn's modified file. With the original eng files steam gave out at the same location each time (just north of Baltimore)no matter what I did to tweak throttle and reverser. I've just finished a run with Mervyn's file and the unit performed superbly. Reasonable separation between steam useage and generation given varying road and driving conditions. Boiler pressure maintained. Stack exhaust appropriate. Plenty of power. As far as I can tell, everything else is fine. Injectors working fine. Water level and fire right on.

    Mervyn: many thanks! You've made the unit really functional. I appreciate you jumping in with the file. Really nice job. Best wishes to you.

    Barry

  6. #6
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    Default RE: J3A Hudson Steam Generation vs Usage

    Bill

    I do not need that extra 10% in my Auto fired files, because I restrict the injectors to 1 operating unit. As far as I know, the injectors are the only things on an MSTS steam engine that use steam, other than the cylinder unless you run winter passenger services. Even then, you would not need the extra.

    That ese eng file has not had a lot of work done on it. I just wanted it to run Marias without running out of puff.

    Beer is not a matter of life and death. It is much more serious than that.
    mervyn.

  7. #7
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    Default RE: J3A Hudson Steam Generation vs Usage

    Barry

    Glad it does the job for you.

    Beer is not a matter of life and death. It is much more serious than that.
    mervyn.

  8. #8
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    Default RE: J3A Hudson Steam Generation vs Usage

    Mervyn,
    You are correct that you don't need as much extra on Auto fired locos as on manually fired ones. On a manually fired engine, there are 3 non-cylinder uses of steam: injectors, "basic steam usage", and pop-off loss. The latter isn't a problem when Otto is firing. I recommend as much as 15 - 20% difference between boiler capacity and exhaust limit for smaller locos where the injector steam usage can get to be a real problem. And smaller locos are where most of my .eng file setup efforts are directed.
    Consider a small loco needing about 15,000lb of steam when working hard. The injectors might use 1,000lb under those conditions, and another 400lb for a realistic "basic steam usage". That leaves almost nothing for pop-off loss.

  9. #9
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    Default RE: J3A Hudson Steam Generation vs Usage

    Bill

    I must say that is an interesting scenario, but not one, in my own opinion, that warrants an increase in boiler capacity for steam generation. If the eng file is properly set up the steam generation should by and large keep up with demands placed on the boiler.

    The main cause of drops in the generation rate is the large difference in Max and Ideal firemass while under the control of Otto who always does things to the max.

    Over here, steam engines are set up with an exhaust limit that is higher than the boiler capacity for generation, probably for the same reasons that you advocate an increase in boiler capacity.

    I am not quite clear on the term pop-off and why it/they should cause a loss of steam.

    Beer is not a matter of life and death. It is much more serious than that.
    mervyn.

  10. #10

    Default RE: J3A Hudson Steam Generation vs Usage

    Mervyn,
    >
    >I am not quite clear on the term pop-off and why it/they
    >should cause a loss of steam.
    >
    I believe Bill refers to the safety valves exhaust steam quantity, which can be quite high, depending on the settings between the boiler max pressure and the pressure value set for the valves shut down.

    Jorge

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