Speed Matching Tips and Tricks


I’ve been watching the statistics on what’s driving traffic to my blog and noticed a lot of it is searches for Bachrus and/or JMRI so I thought I’d post an update.

There are three components I use in speed matching, the Bachrus Speedometer, JMRI, and a Digitrax PR3. As I have now successfully matched three very different locomotives from three different manufactures with three different decoders I have some tips and tricks.

  1. A good drive train can make all the difference. My Kato SD38-2 and Proto 2000 SD60 were very easy to speed match as they run well at low speeds and across the range are smooth runners. My Athearn SD45T-2 however has been a bit tougher, it varies quite a bit even at constant voltage so it can be frustrating maintaining constant speeds to set up your speed table.The takeaway here is that the easy of matching can vary quite a bit between locomotives so don’t give up if things aren’t going smoothly.
  2. If you are using a Digitrax PR3 and JMRI keep the PR3 plugged in to the USB port even when not in use. This solves two problems I’ve run into, first it helps ensure that the correct driver is always loaded and second it ensures the COM port assigned is the same.At least on Windows 7 I’ve observed that in some cases plugging in the PR3 will cause Windows to load a generic USB to Serial driver which will not work.If Windows assigns a different COM port to the PR3 or Bachrus Speedometer JMRI won’t function until you open it, fix the COM port assignment and restart the app. While this is simple it’s tedious.Once I switched to a dedicated desktop rather than my laptop these problems have disappeared.
  3. Use the latest version of JMRI and keep up to date, since I started I’ve gone through a couple of versions of JMRI and it has gotten better as versions progress.
  4. If you are going to use advanced consisting (CV19, 20, and 22) it’s probably a good idea to do your speed matching while your locomotive configured for an advanced consist. Digitrax, and possibly other manufactures, alter the BEMF behaviour in consist mode so a table that may work individually may not work the same in consist mode where it really matters.
  5. You probably aren’t going to get a perfect match, even with identical locomotives with identical decoders and identical usage so expect a bit of push and pull between the locomotives. This happens with the prototype and so the point is to get close but you are just going to drive yourself mad if you try to get it perfect.

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