Hi guys, I'm wondering if anybody has used the SpeedTableScript.py from the JMRI project pages in conjunction with a 19" Radius Kato Unitrack loop and different timed blocks in order to speed match their locomotive? From the documentation, you put a locomotive on, start the script. It will call up the locomotive, run it forward for 3 minutes, then start timing at 12 different speed steps, and then interpolates the rest of the middle ones to get it timed and matched. Once you've got a 'gold loco' set up, you can match the rest of your fleet. It will do this in forward and reverse, and even has a custom panel made to work with it for visualization and what not. Now, This is what it *should* do. And i've read on the yahoo group that it does really work. I have yet to get it to, and would love to put together a tutorial on how to make it work for those of us with speed matching difficulties. This seems like the perfect solution for a club to put together for its members, such that ALL club locomotives can be matched and consisted if necessary. So -- any of you seen/worked with this? I'll be working with it more in the next week... so far I can't even call the panel up correctly.
I am an avid user of Decoderpro and have not seen this. I will look closer for it. Is there a feature to help with matching momentum and braking rates? This is why I do not subscribe to the timing version of speed matching as it is incomplete unless the momentum and braking can be matched too.
I have found an easier way. Get the Bachrus USB speedometer and a few rolling stands and you can speed match locomotives in just a minute or so. The key is to use a consistent speed table and a decoder with TRIM enabled. It plugs right into DecoderPro. TCS, Digitrax, ESU, SoundTraxx and Zimo decoders all support CV66 - Forward Trim and CV95 - Reverse Trim. You just warm up the locomotive and then set it on the rollers and set the throttle to whatever speed you want. The speedometer display shows the measured speed, and you just vary the trim CV to dial in the speed you are looking for. I have used this method to speed match 24 locomotives in an hour.
David -- have you tried the script that I'm talking about before? If so I'd like to hear about how its more difficult than your method. My main reason for questioning it is simply because I've already bought all the components to do the loop, and would rather get this to work and use it as an excuse to contribute documentation to the project. Your method would also add what appears to be about 150.00 to my layout, which i'm not likely to get back out of the unitrack/block detection unit. It also creates a very 'hands off' method of matching locos (i.e.: put one on the track, then walk away for 12 minutes. Come back and switch locos, 12 minutes later you're matched entirely). If you've used the script and panel I'd be very interested to hear your experiences.
My method only requires about 16 inches of track, or as long as your longest locomotive, and only a minute or so of time. There are other issues of a constant curvature calibration. The speed is calculated on the curvature and an irrational number (Pi), and the velocity around a circumference is not the same as the velocity in a straight line. The differences are minor, but it is just my preference. Mathematical interpolation is in itself a semi science, and is not necessarily simple and direct. Since the motors themselves in the locomotives only have limited domain of linearity, simple interpolation will not yield correct results. It is because of the limited linearity that there are Kick Start and Momentum CV's to help give a more linear response low speed response. Based on looking at the hysteresis of the magnetic core implies a spline based interpolation. I have found that using the same brand of decoders and the same brand of locomotive allows the use of the 28 step speed table, and the trim is a simple scaling factor. In fact, by clamping the top speed to say 70 Scale Miles per Hour, I can easily match Atlas, Kato, Intermountain, Life Like and just about any other locomotive to run with any other locomotive. All I have to do is just adjust the Kick and Momentum. But since I have done so many of these, that is usually a trivial effort.
I would appreciate it if you would "PM" me with some further details on your method, with specifics re: proper equipment, etc. I model "N" scale, and have an "NCE" PowerCab. I am anxious to see if this idea will work with that system?? Jim Jeffries
While I do appreciate the info on another way to speed match, my request was for this specific method. I've already built the board to be incorporate into my layout, with the 19" radius curves, already have the block detection, and candidly am specifically interested in the challenge of getting this set up. I can also see it being used while I'm working during the day -- put a locomotive on, set a timer. 15 minutes later, switch them out. It requires 0 attention to work, and can be remotely monitored with a computer.
Philip: Did you succeed using SpeedTableScript.py ? I'd like to hear about your setup and how well the script worked.
...and how well does it work with momentum and braking? My efforts have shown that even if I can speed match locos the momentum and braking rates will be different on each loco to run better together.
I saw one of these operate at the Texas Northern Model RR Club in Dallas. Slick. I have asked a few questions there but it is all beyond my capability. There are some individuals you can contact at the club who might help.
