Running two different performance engines together in DCC - how ?

[Anonymous]

I've got a couple of Spectrums and I have an NCE system and decoders.
One of my engines is faster than the other so running them in a consist is not pretty. I've heard that the whole concept of DCC can solve it - but couldn't find any particular info in NCE manual nor online. Does it have to do something with BACK-EMF ? Do I need different system or decoders ?

[dave9999]

You need to adjust the CV values. You can simply change the start, mid and top
voltages and see if that solves the problem. If not you will have to start tinkering
with the speed curves until you get them to match speeds. Dave

[Anonymous]

Wow, that's pretty complicated ! What's this back-emf feature for then ?
The one many describe as cruise control of DCC ?

[Anonymous]

Back-EMF monitors the voltage and current on the motor to keep a constant speed regardless of gradient - if you take a heavy train down a grade with a Back-EMF equipped loco it will maintain a steady speed rather than running away - likewise, when climbing grades it will not require you to open the throttle any more to maintain a steady speed. This is particularly handy on locos without flywheels as it allows better slow running than would otherwise be possible for switching, as well as the previously mentioned benefits. BEMF decoders tend to be more expensive though, so you may decide you only want to invest in them for certain locos (I intend to fit my British steamers with them when I go DCC, along with a few other locos that have trouble with crawling along for switching work). Hope this is of help!

[cacole]

You need to create a custom speed table for the faster locomotive to slow it down to the same speed as the slow one, or speed up the slow one to match the faster. The NCE documentation that came with the decoder should have a table listing all of the default speed table values. Take the faster locomotive and reduce each value by 10 and create a custom speed table, or increase by 10 for the slower locomotive. Then change CV29 to indicate that you want it to use the custom speed table. If it is still too fast (or slow), go through this procedure again, reducing or increasing each value by 10, and save it as a second custom speed table, change CV29, and see what happens.

There is a computer program that can automate this process if you have a DCC system with an RS232 interface, but I don't remember the name of it. Perhaps someone else will chime in with that information for you.

[dave9999]

QUOTE: Originally posted by cacole

You need to create a custom speed table for the faster locomotive to slow it down to the same speed as the slow one, or speed up the slow one to match the faster. The NCE documentation that came with the decoder should have a table listing all of the default speed table values. Take the faster locomotive and reduce each value by 10 and create a custom speed table, or increase by 10 for the slower locomotive. Then change CV29 to indicate that you want it to use the custom speed table. If it is still too fast (or slow), go through this procedure again, reducing or increasing each value by 10, and save it as a second custom speed table, change CV29, and see what happens.

There is a computer program that can automate this process if you have a DCC system with an RS232 interface, but I don't remember the name of it. Perhaps someone else will chime in with that information for you.

Yea, what he said.

DecoderPro is the software. I downloaded it awhile back just to play around
with it. I like it. Now I need to get the interface cable (and a laptop, since my
computer is not in the train room). Dave

[Anonymous]

Definitely DecoderPro -- it's a life saver. But in the meantime, the simplest way to "tune" DCC locos is to use CVs 2, 5 & 6. CV2 sets the starting voltage, CV5 the top voltage, and CV6 the mid-point voltage. Using these three, you can get your locos operating pretty close together (and more prototypical to boot, since the top speed of an unmodified loco approaches 200 scale MPH at full throttle [;)]).

Rather than going into all the ins and outs of programing these three CVs here, I suggest you go to the Digitrax site and download their Decoder Programming Manual. Even if you're not using Digitrax decoders, it has a great explanation of how to use these CVs (and the full speed table, if you're adventurous) to customize the locomotives response curve. You can find it at http://www.digitrax.com/pdfdocs.php .

[ClinchValleySD40]

Very simple to get them all to run together well using just Vmid and Vmax. A quick method with nothing else needed. Only drawback, you need to make sure the decoder being used supports it.
I run Atlas, Kato, P2k, Stewart and Athearn in all kind of mix/match combos and have no problems at all.