Slowing down Athearns locomotives

power boat jim Jan 17, 2021

  1. power boat jim

    power boat jim TrainBoard Member

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    Does anyone know of a way to lower the speed of tsunami equipped locos at any given throttle setting? They seem to run a bit faster then most. I seldom run even my scale trains past 40 on the digitrax controller. It would be nice to have the Athearns locos run close to a scale speed at the same setting.
     
  2. Mr. Trainiac

    Mr. Trainiac TrainBoard Member

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    Speed matching? Go into the speed table and just drop each of the 28 steps down a few notches. The easiest way would be to set a top speed and then make a linear speed table between your Vstart and Vmax.

    If you have a PR3, you can use JMRI DecoderPro.
     
  3. power boat jim

    power boat jim TrainBoard Member

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    I dont have any programs. can this be done on pen and paper and entered in a cv on the digitrax throttle?
     
  4. Mr. Trainiac

    Mr. Trainiac TrainBoard Member

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    Yes, but it can be more time consuming. You might want to get the Tsunami manual and check which of the CVs are for the speed table, I want to say 64-93 or something in that range. Are you trying to match up with another slower locomotive so they can run in a consist?

    You can use programming on the main to set the top end CV so they run at the same speed, and then repeat that process for 50% throttle. You can add more intermediate matches if you want, like 25 and 75% throttle, but more than that is probably unnecessary.

    If you are not speed matching, just slowing it down, calculate the top speed you want and then make a linear relationship from the two endpoints. A calculator is handy here, its just y=mx+b
     
  5. power boat jim

    power boat jim TrainBoard Member

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    Yes just trying to slow them up a bit. It seems access to the speed table requires some sort of binary code to be changed. I got into the vmax cv. I was afraid to adjust it since I dont know what the default setting is. You are correct Dont need to run any faster then 1/2 throttle. Whats the hurry? If you know what to adj the Vmax to I would try that.
     
  6. Mr. Trainiac

    Mr. Trainiac TrainBoard Member

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    All speed step CVs can be in between 0-255. I think the default for the top speed is 255. However, I am not sure what it looks like in the Digitrax throttle. I do not use Digitrax, so I can't really help with the actual programming.

    Even if you are unsure, do some experimenting. If you mess something up and can't fix it, just do a factory reset with CV8 to restore the defaults.
     
  7. power boat jim

    power boat jim TrainBoard Member

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    ok that said I can turn down the top speed (vmax), will that cut the voltage all the way down the dial by the same percent it gets reduced from 255?
     
  8. power boat jim

    power boat jim TrainBoard Member

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    Turning vmax down to 150 worked well. It is only slightly faster than the scale trains at a setting of 25. they run pretty equal up to 10. Thank you.
     
  9. Mr. Trainiac

    Mr. Trainiac TrainBoard Member

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    You can also mess around with Vmid. There are options for using the full 28 speed curve, or just using a 3 point curve. In JMRI, you just click a box, but you may want to investigate the direct CV option for that too. Decreasing Vmid a bit could slow it down in the mid-range, especially if low speed is set up decently well.
     
  10. power boat jim

    power boat jim TrainBoard Member

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    Thanks I will give vmid a try.
     

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