30 MPH Max Speed "Matching" of ALL my Locos.

I was reminded by Bob Stack at the MRNSW-27 Convention, that it was ages since I added something to my Blog. With no progress on the layout to report since I last posted, I thought I’d write about what I have done to my locos.

I need to Speed Match my locos for rear end banking and double heading, both used regularly as trains tackle the Liverpool Ranges from both sides, on my “Main North”.

I’ve observed that 99% of trains on exhibition and home layouts are run at speeds below 30 MPH. While the “Main North” is located in a 30’ X 30’ garage/room, it does not have any long straight runs and with many 24 inch “curves”, operating at near prototype maximum speeds is impossible. I wonder how many model railroaders operate their locos at their maximum prototype speeds.

With this in mind, and to utilize 100% of my throttle range, I’ve reduced the Top Speed of ALL of my locos to 30 MPH. This means I can double head or bank with ANY loco combination, making it safer for my crew, inside and outside of the locos. That is all locos perform the “same”, speed wise, irrespective of what the prototype does.

This LINEAR Max 30 MPH Speed Table plus using 28 Speed Step Mode instead of 128, provides whatever Speed Step is displayed in my NCE Procab equals the actual Miles per Hour of my locos. At Speed Step 10 the loco is travelling at approximately 10 MPH, at Speed Step 20 the loco is travelling at 20 MPH etc.

For speed calculations, I use my Speedo Car or a “Speed Trap”. For me nothing technical, 36 inches of straight track, a Stopwatch and a suitable Scale Speed Calculator. A good one is at Rob Paisley’s Circuits for Model Railroads at: http://home.cogeco.ca/~trains/rroperat.htm

Adjusting the decoder’s CV 5 will provide “close enough” speed matching. You may need to adjust CV2 to get a slow speed at Speed Step 1.

Most of my sound locos have Soundtraxx Tsunamis, that don’t support CV 5. For them you can reduce the loco’s Top Speed by two methods:
1. Selecting a Speed Table in CV 25 and programming CV 66 (Forward) and CV 95 (Reverse), to less than 128 – lower the value, the slower the speed. See Tsunami Manual.
2. Selecting the “User Defined Speed Table” (CV 25 to 16) and making a Speed Table.

As with all programming, especially sound decoders like the QSIs and the Tsunamis, I use Decoder Pro, selecting the POM (On the Main), Mode.

Using Decoder Pro using Operation Main Track Programmer – POM, for each of the locos, select Speed Table, “check” the “Use Speed Table” (shown right) then select “User Defined Speed Table in the line above the Table. Place the cursor on the Slider for Speed Step 28 (CV 94) and drag down the Slider to about midway (120) and then select the “Match Ends Tab. This adjusts all 28 CVs to provide a LINEAR (Straight) Speed Curve. Then select Write Changes”. Decoder Pro, programs all the appropriate CVs, in the loco.

“Time” the loco at Speed Step 28, through the Speed Trap (36 inches of track). Repeat the above sequence until the loco travels at 30 MPHs - 6 seconds for 36 inches.

Do this procedure to ALL of your locos and they’ll all run the same – speed wise, making double heading and banking easier.

Fine Tuning the Soundtraxx Tsunamis

Tsunamis “out of the box” provide a too high slow speed and a noticeable jerk between the lower Speed Steps, when using 28 Speed Step Mode. Operation is better with 128 Speed Steps.

My Tsunami adjustments are based on what Bruce at Litchfield Station posted some years ago and a long discussion on Back EMF on the Soundtraxx Yahoo group during June/July2010.

For my above Max 30 MPH Speed Table, I need to use the 28 Speed Step Mode, I’ve fine tuned my Tsunami equipped locos for 1- 2 MPH speed at Speed Step 1 & smooth jerk free acceleration by adjusting a few of the motor performance CVs, namely:
Program both CV 3 & 4 (Momentum), to “0”
Program CV 209 to “10”
Progressively increase CV 210, starting with “1”, until the loco moves, at Speed Step 1, albeit a little jerky.
Program CV 209 increasing by 5 until the loco is smooths out.
Reducing CV 212 (default 255), will further slow down the loco.

Using 28 Speed Step mode with the Maximum Speed reduced as per my method, the voltage increment between Speed Steps is about 1/3 of the default Linear Table, so the jerkiness between Speed Steps has be all but eliminated.

Steam Chuff Rate or Diesel Notching Speed Steps, may need to be adjusted if you use the 30 MPH Max Speed Table. If this is a Diesel loco, then CV 116 would have been programmed to maybe “46” so the engine “Notches up every 14 Speed Steps”. Re-program CV 116 to “7” or “39”. For Steam, re-program CV 116 to “80” and then test for 4 Cuffs per wheel revolution at 10 MPH. May be time to use the Tsunami Manual or go on line to Soundtraxx at: http://www.soundtraxx.com/

When finished with adjusting the Tsunami, adjust CV 3 & 4 (Momentum) to your desired values.

If you have not used Decoder Pro for programming decoders, for details and what’s necessary, see:

http://jmri.sourceforge.net/help/en/html/apps/DecoderPro/index.shtml