Matching Speed of Engines


N

North Bound

Bryan
I have an NCE PoweCab control. Just purchased two Kato SD40s at a show that had Digitrax DN163K1C Decoders installed. The seller said he had speed matched them but when I tested them in a consist (by not coupling them together), one engine was considerably faster than the other.

So my question is, how do I go about programming one of the engines to match the other? Looking at the NCE manual it isn't really clear to me. I am new to DCC so any advice would help.

Related to that, how close in speed is good enough? Do you ever get two engines to be equal? If not, do you stick the slightly slower engine in front or in back in a consist?

Thanks,
Bryan
 
Bryan, speed matchig a consist is much different than trying to get two locomotives to run at exactly the same speed when they are running light. Two identical engines can have different amounts of tractive effort dur to difference in gear meshing, lubrication, weight distribution, and about 100 other variables. When you're consisting two engines, you are trying to get them to run as a pair. The one with more tractive effort will go on the front and, in effect, "tow" the second engine. The second engine is still contributing some tractive effort to the consist, just not as much as the first.

First, check your manual for speed steps. See what each locomotive is set to by reading back the values. Run them separately and see how much time it takes for each to get to two given points. If one is faster than the other, go to CV 29 and try adjusting the variables there for start speed, max speed, mid speed, and acceleration. You'll have to experiment some but you should be able to get them running at about the same speed. You can now consist them and see if they work better. You may find that having the lead locomotive faster works better than trying to have them both run at the same speed.
 
I have a couple locos that I always run in a consist but one is a little faster than the other. I actually keep it second and put the slower unit in the front as the weight of the train slows the faster unit to the same speed as the first one. As Jim pointed out, there are many variables involved in getting them to run the same speed.
Hope this makes sense... just had my first gulp o' coffee for the morning!
 
good advice so far.

DCC has lots of little tricks you can use to help speed match.

everyone has there own idea and results they can live with.
What I like to do is this

set the controller for 128 speed steps
set the start voltage so that the loco will start to move on the very first speed step.
then I adjust the mid rage so that they will be close in medium speed.
after I get that done I will adjust the accell and decell speeds.
If its all working out I can get most locos to follow each other around the layout and not move more than a foot or two apart over a 30' mainline. Even if one is still a little faster I like to put that loco up front so that it does not put slack in the coupler and separate in tighter turns.


it can be time consuming but in the end it works out great.
and dont forget. after you get them all dialed in go back and read the values that you had set and write them down. this way you wont have to try all over again!!!

Trent
 
Excellent tips. Thanks. What you have said about speeds makes sense. Not sure how "close" they need to be taking into consideration what everyone said. What I think I will do is match them closer to what they are then experiment some with them in an actual consist. This is a great site and I have learned alot from everyone. It really helps for people such as myself just getting started in a hobby that requires a lot of different skills and knowledge. Now I am going to grab my cup of coffee and off to work. Won't have time to try this until I get back home :)
 
Bryan, you're welcome. Almost everything I've learned about DCC, they guys here taught me. Both the benefit and bane of DCC is that's it's almost infinitely adjustable. I think I spent two hours fooling with one engine when I got my Digitrax Zephyr, adjusting everything from speed tables to making the Mars light work. I finally figured out that I really only had to adjust three or four variables to get my engines to run "good enough". Now, when you get a sound equipped engine, you can really spend some hours on those guys. :)
 
Raising a thread from the dead, but is there use to be a site outside fo digitrax that helped answer DCC question and gave guidence of installs & wiring. Any such sites that deal with these speed steps and consists set up. The manual from digitrax has some pretty heavy verbage.

This thread has been helpful and I searched this site for "consist" b/c I have near 30 locos that need to be matched.......
 
Perhaps I missed seeing it earlier, but has anyone mentioned the need to cancel BEMF sensing in all consisted decoders? It is important because speed mismatches over a small percentage, very small, could have one decoder fighting the other(s) trying to get its BEMF to remain flat.

-Crandell
 
Selector said:
Perhaps I missed seeing it earlier, but has anyone mentioned the need to cancel BEMF sensing in all consisted decoders? It is important because speed mismatches over a small percentage, very small, could have one decoder fighting the other(s) trying to get its BEMF to remain flat.

-Crandell
Click to expand...

That's what I've found as well. When running as a consist, even with the lead locomotive running faster than the trailing one, I would have them fight each other on different layouts.
 
Ya know, this is why this is such a great forum, and why bringing a thread from the dead with a related question is a good idea. It gives people who may have missed it a chance to chime in. Crandell, I have two locomotives that run within 2 scale mph of each other light but fight like cats and dogs in a consist. I had adjusted every variable I could think of but back EMF never came into my mind. Now that you've mentioned it, I'll bet that's exactly the problem. Digitrax has Decoder Assisted Consisting and the NCE decoders I have support that although, strangely, Digitrax decoders don't. I just never put two and two together. I'm going to give it a try with these two and see if I stop them from fighting like cats and dogs. :)
 
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