Speed matching locomotives

Not really knowing what to do and only having read about speed matching from various forums and on-line sources I was a little hesitant about pulling back the covers on DCC and getting my hands dirty with CV's.  But once I got my feet wet it wasn't near as bad as what I first thought it would be.   I have heard a lot of others complain how tough it is or how much of a pain in the ass it was, so I thought I would  attempt to explain the method that I'm using to speed match my locomotives.

Disclaimer:

Please bare in mind that this is what works for me.  In no way am I trying to imply that this is the "Best" or the "Only" way to do this. 

This has been a grey cloud that has been hanging over my head ever since our modular group switched over to DCC back in 1997.  It took me a little while just to figure out how to use my Digitrax Super Chief system.  My friend Jim, who understood it, got it hooked up, and then went away to Boot Camp for a year.  So for the most part, it just sat in the basement, hooked up to the layout.  I never used it other than to test the new locos that I had picked up over time.  It sat there like an 800lb gorilla, just teasing me.  I knew the power of it, but just didn't know how to control it.

After Jim got back and once I broke down and bought one of the DT400 throttles [and pitched the DT100's into the nearest creek], things became a lot clearer and simpler.

Slowly but surely I began to fiddle with it as the new layout came to life.  At which point I had no other choice but to learn it if I wanted things to progress.

By the time the layout became operational I had a good grasp on how the system worked.  I felt comfortable enough to start to explore the inner working, namely the CV's.  As my layout progressed so did another one of our members layout.  We were both itching to be able to run our locos in a consist without having to find ones that ran together at roughly the same speed like we had done on the modules for years.  Knowing that DCC would let us do just this, the research began in earnest.  Thank heavens for the Internet!

I quickly came to the conclusion that there are as many different ways to speed match as there are DCC systems!  But which one would work for us?

After reading about five different ways to speed match that we found on the internet, we settle on two articles that sounded the simplest.  Both articles made use of the JMRI software.  The first method used the Golden Locomotive method.  The second used an electronic device that sets over the tracks that reads the speed of the loco as it passes through two infrared beams similar to a chronometer. 

I started playing with the "Golden Loco" method so I could try and get a handle on the basic idea and the CV settings. While the Golden Loco method looked the simplest, it took a little bit of time to speed match each loco.  

Basically with the golden loco method, you get one locomotive set to run to what you think is right and looks good to your eye.  Then mark that loco and you will use it to match the rest of your fleet to it.  This is done by running both locos at the same time.  With one throttle, start the golden loco set at a certain throttle setting, then set the second throttle to the same setting as the first throttle.  You can then adjust the values of each CV of the second locomotive until it's running at or close to the same speed of the Golden locomotive.

Some folks will do this using only the Start, Mid & Max settings [CV's 2,5 & 6] while others will use the full 28/128 step speed table in conjunction with the JMRI software.

As long as this video is available, this is the one that I started out with.  While he uses an NCE system, the basic idea can be translated to any DCC system.  Since I already had the JMRI software and was somewhat familiar with it, I did not follow his instructions to a "Tee", I took his basic ideas and modified them to my likings using the 28/128 step speed table. 

The second video shows him using the JMRI program and while there are other ways of using it, he gives a good example of how some of the features work.  He does not explain it in a real detailed way, but you can get the jist of how it works.

Speed Matching #2, the Golden Locomotive method

Speed Matching #3, using JMRI overview

Along the way I encountered some problems and ran across a fellow from one of the online forums who was gracious enough to take the time and help me via emails and phone. He explained to me that the best way was to use the 28/128 speed step tables using the JMRI program.

He walked me through the program, explaining most of the major settings that I would need to make to get started and the purpose behind them.  Then he sent me a file from one of his KATO C44-9w locos so that I could flash it to one of my C44-9w's and see not only how the settings looked on screen, but also how the loco responded to these settings.  This was a great help.

He told me to keep this file saved for future reference and to use it as template for the rest of my fleet, then change necessary things to my likings and adjust the setting for each locomotive if  needed.

Two major things that he pointed out was to use a similar speed table settings for ALL of my locos and then make use of CV66 & CV95  to fine tune the speed of each loco without adjusting the speed table.  These are the Forward & Reverse trim settings.  I'll cover these later as I explain my method.

OK, here are the "Tools" that I have:

A Digitrax Super Chief  [ any Digitrax system can be used as well as other brands]

A Laptop with WinXP [Win7 can be used, I've just got WinXP]

JMRI / DecoderPro3

A LocoBuffer II USB [an interface used to connect my laptop to my DCC system]

A loop of KATO  #20-132  13-3/4" [348mm] Radius 45° curved track.  [Smaller can be used, I felt this was a decent size to allow six axle power and steamers to run smoothly]

One MRT Accutrack Speedometer. 

I bought mine from Ulrichmodels. 

The reason I invested in the Speed Tunnel is because it does a great job of replacing the "Golden Locomotive" and it remains constant unlike a locomotive can as it gets broke in over time.

I won't get into how to set up and make the connections of my system as yours might be different.  I'll just try to explain how I make use of mine.

One note, I will be showing you how to setup a Digitrax decoder with a Digitrax System.  Each decoder's page will have different settings depending on what each model includes and what the manufacturer designed it with.  Thus a Digitrax decoder page will look different from what a TCS decoder page does.  I will suggest that you start with one brand and stick with it until you feel comfortable enough to delve into another brand of chip.

Some folks have said to stay with one brand of chip so that they will program the same and should have the same results.  While this can't always be done due to design of the loco [one Mfg may not have made the chip needed yet, etc, etc]  I started out using Digitrax but I plan to start using more TCS as I buy more chips.  They both have their own good points.

Once things are setup, the connection have been made and are working and you have your chip installed and programed with the basic settings: including a chip/loco number and then entered into the DecoderPro3 roster, you can begin.

This next step is very important.
Start by cleaning the track and wheels of the loco, then warm the loco up by letting it run for 5 - 10 minutes.  If the loco is new, be sure to break it in by running for 30-45 minutes as varying speeds, both forwards and reverse before attempting to match the speed.  While the loco is warming up, I usually grab a soda or make a pit stop.

Next, turn on the Accutrack Speed Tunnel.

 

Open up DecoderPro3.

On the main screen of DP3, choose "Programming On Main" in the lower right hand corner.  I was also told to set the Programming Mode to "Direct Byte".  Now choose the loco from the roster list that you're going to speed match.

I do a quick check of the settings on each tab to make sure they are still set properly.  Again, the settings you see on these screens are my choice.  You may want to explore how other settings will effect your locos.

One thing that I was told to always do, is to be sure and set the "Analog Conversion Mode" to off if you do not plan to run your locomotives on any DC layout.  He explained it to me that this way the command station and the chip have one less thing to decipher.  If you ever do need run them on a DC layout, just come back to the JMRI and change it to "ON" and write it to the chip.

I also make sure that the Acceleration & Deceleration Rate [CV3 & CV4] are set to "O" or OFF as I am speed matching my locomotives.  Once I get them programmed, I come back in and adjust momentum.

BEMF should be set to "O" or "OFF" [Digitrax: CV57 - TCS: CV61].  These can be turned back on after the speed matching is done.

However most of the things that I have read while researching speed matching is that most people leave the BEMF off if they are always running multiple units in a consist.  

A note on BEMF...

Although BEMF is a valuable feature, there may be situations in which you prefer to turn off the BEMF. 

The only time BEMF can become a problem is when running two or more engines in a consist with them all having BEMF turned on. If one of the engines runs slightly (and I mean SLIGHTLY !) slower or faster than the other, the BEMF will be constantly fighting trying to even things out.
If the second engines senses things are starting to slow (because it pushes the lead engine for a split second) it will try to increase the speed to mantain it's preset level. The lead engine feels this slight push and thinks it's starting to go too fast, and the BEMF tries to slow it down. The multiple units fighting against each other can create some not so smooth operation. This is why most guys turn BEMF off when using engines in consists.
There have been times on a Digitrax decoder where I've had to turn it back on but with only a value of 1.  I've done this so the unit responds a bit better.  I've found this to be helpful on older locomotives with a faster motor and older chips.
Again, you can always turn it on or off and play with it.  JMRI makes this very easy to do with a simple click of the mouse.

TCS has a self adjusting BEMF or it can be cut-out at a predetermined speed.  You can read more about TCS's BEMF and Dither control here.

If everything is set to the way you want then you can begin.

On the Speed Table screen, I set the first slider [or CV67] to 30 and set [CV94] to 140.  Next I click on "Log Curve".  This will set the speed table so it looks like this

I chose the "Log Curve" so the throttle has a quicker response at the lower speeds [this covers 0% to 49% of the throttle] and slower response at the higher speeds.

I start with the loco running in the FORWARD direction , I set the start speed first.  I turn the throttle to 1%, if it does not start moving, I simply increase the slider for speed step 1 or CV 67 by a value of 5 until it begins to crawl at a speed to my liking.  Another thing I might do is to adjust CV65 [The kick start value which can be found on the "MOTOR" tab or page] which gives the motor a little extra shot of voltage to help start the motor turning if the unit is an older unit or fairly new and still a little stiff.  Normally a value of 2 is sufficient for most locos.

Second, I turn the throttle to full speed or 99% and see what speed the Accutrack reads.  If it's not at the 68-70 smph then I adjust the Forward trim [Cv66] up or down until the desired speed is reached or close to it.

Third, I turn the throttle down to half speed or 49% and check the Accutrack for the speed.  This should be around 58-60 smph. 

Fourth, I turn the throttle down to 25%, the speed should be around 38-40 smph.

Fifth, I turn the throttle down to 12%, the speed should read around 20-22 smph.

I'm simply trying to get close to the setting that I want by doing it this way, it's very similar to using the Start, Mid & Max settings.

But by using the full speed table I can now start fine tuning the locos speed.  If you want your locos to run faster or slower, simply adjust the over all Log Curve" by using the Forward and Reverse trims.

This is where CV66 and CV95 comes into play.  If the speed is too fast or too slow you can change the value of that CV to raise or lower the speed.  But note this, CV66 & CV95 will effectively raise or lower the entire speed table [CV67 -CV94] as a whole, not each individual CV or slider.

Values that can be entered into CV66 and CV95 range from 0 to 255.  Halfway point is 128.  Any value under 128 will slow the speed down, any value over 128 will increase the speed.   

You can change the CV value by a value of "1" if needed and sometimes it will make a difference, most of the time I change the value by 5 or 10 until I zero in on the speed.   Once you have the locomotive running close to what you prefer, then change direction and repeat the process.

I have heard and found out for myself that very seldom does a locomotive run the same speed in both the forward and reverse direction.  For that matter, even the same make and model will sometimes not run at the same speed right from the factory.  By having a separate trim CV for both the Forward and Reverse direction, makes it very handy to get the speeds match in both directions.

At the time I wrote this up, I know that some chips do not have both CV's available.  Both Digitrax and TCS does, while NCE chips do not.  One reason why I stick with Digitrax and TCS for my chips.  I'm sure there are other brands of chips that have both, but I'm not familiar with them.


I came up with these speeds by setting my golden loco to speeds that I thought looked pleasing to my eyes.  After getting the Accutrack tunnel I ran the loco through it to see what the Speed Tunnel showed for speed at each throttle setting and then wrote them down and taped them to the speed tunnel for reference.

Throttle settings;
99% = 70 smph
49% = 58 smph
25% = 40 smph
12%  = 22 smph 

Again this is what I felt was right to me, feel free to change them for your needs.



A few side notes...

For awhile I also struggled with getting the speeds to match at each of the four throttle settings.  Sometimes I could keep the speeds matched at 12% and 25%, but at the settings of 49% and 99% they would be higher  than what I had on the chart, other times they were lower.

After getting a good batch of my locos speed matched and running them in a few operating sessions, I found that I would normally run my trains at about 15% of the throttle setting [or speeds of 20 smph max] and very rarely ran at speeds higher than 25%.  It then occurred to me that as long as I can keep the speeds matched close at the 12% to 25% range then things should be OK.  If they ran a little different at higher speeds they would not be as noticeable because of two things; One, I don't run them that fast and two, several things come into play at the higher speeds.  The slower running locos will keep the faster locos at bay because they run slower and, the weight of the train will tend to even out the locos.  When I say they run faster, it's not by much but you can see the difference if you were to uncouple them.  The faster ones would pull away but not at a rockets pace.

Another thing I noticed was that even though two locos may not be matched perfectly, once they get running they seem to run very well together, at least one isn't spinning it's wheel and the other isn't being drug along behind the first one.  You may notice the couplers may bunch or stretch as the units are running.  This may be very apparent when the consist starts to move from a stand still.  You will see the faster locos start a little quicker than some of the others, but soon the others will begin to move as well and then even out.  This where and why I add just a bit of momentum, it helps to diminish the bucking and jerking at start up.

If you watch the prototypes, you will see this action as well.  GE units use to start at a slower pace than say EMD's, you would see the units buck and jerk as they begin to move, but once they're moving they would tend even out.

 

After matching a number of locos and actually running them in consists in several operating sessions I have come to the conclusion that speed matching is not Rocket science.  The term "Close is Close enough" really applies here. 

Once you get a few locos under your belt you'll become familiar with what setting you'll need to change and how much to change each value.  It just takes a little playing with. Then you should be able to match the speeds of your locomotives faster than what time it took you to read this novel.  If everything goes as planned, I can usually have a locomotive matched for speeds in about 15-20 minutes.

I hope this helps out?