Hi guys I am having some issues with my consist. I have an Atlas GP40-2 and an Athearn C44-9W that I am running as a consist. The GP40-2 moves before the Dash 9, which creates a few problems. Many times the GP is spinning its wheels waiting for the Dash 9 to move. I am using a NCE PowerCab DCC system. Does anyone have any ideas to match the startup speeds of the two locos? Any help is appreciated.
Darrell
You need to set CV2 (Start Voltage) to a higher value for the C44-9W’s decoder. Start with a value of 6 and increase in increments of two until it gets close.
If that doesn’t solve the problem, you will have to create a custom speed table for one or the other of the locos, which can more easily be accomplished using Decoder Pro instead of the PowerCab, but that also requires a computer link to the programming track through a PR3 or similar hardware device.
The creation of a custom speed table is far too complicated to be explained on these forums, and using the PowerCab alone is going to be a tedious, hit-and-miss process.
Until you gain more experience and a better DCC system than the PowerCab standing alone, you’re better off not running these two locomotives as a consist.
Super easy to do with NCE. Program on the main. Change CV #5 and #6 on the “bad” loco. Start with a value of about 120 in CV #5, go up or down in increments of 10 until it is where you want it. I usually use a value half of CV #5 in CV #6. Let us know how it works.
Thanks guys for your help. I went back to the manual and reset CV2 on both locomotives until they matched at startup. Consist running smoothly now.
Thanks again.
Before you do anything, a little more information is required. You said in your other post that both decoders were NCE. Do you happen to know which particular decoders they are?
You also said that the GP40 moves before the dash 9. At what speed step does the GP40 start to move? And at what speed step does the dash 9 start to move? Ideally you want the locos to start, and run smoothly, at speed step 1. Set your PowerCab to operate at the 28 speed step setting when you check this. The reason why I ask is that while you may have to raise the Vmin setting of the dash 9 to get it to start sooner, you may also have to raise the Vmin setting of the GP40 to get it to start at speed step 1. If the GP40 seems to move too fast at speed step 1, then you will need to lower Vmin.
I also asked in your other post if you could run the two locos consisted but uncoupled to determine which of them ran faster. Did you try this? The reason why I asked this is because I have been doing some speed matching for a friend. And typically while it takes a higher value of Vmin to get the Athearn moving, the loco will run like a scalded cat at full speed. I have a speedometer that I use for checking the speeds, and generally the Atlas units are in the 80 to 90 smph range, and the Athearns are between 100 and 110. What this would mean for you is that even when you get the locos to move out slowly together, when you get to full speed you’ll still have that wheel slipping going on except it will be the Athearn unit doing the slipping as it drags the Atlas. If that’s the case, then Vmax will also need adjustment.
And while you’re thinking about all this, you might as well try to make a determination as to how fast you really want your locos to go. You might want to consider slowing down both locos so that they run at some realistic speed on your railroad.
They just have to be close, not dead on. People consisted locos using DC and short of adding diodes to the motor lines and adjusting the voltage in nearly 1 volt incremenets, there was no speed matching. Yet they worked fine.
You don;t want one loco going 20smph and the other trying to go 50smph at the same speed step, but the obsession of getting locos to run exactly in lockstep I don’t really get. While it might be a great achievement to have a pair of locos circle your layout while remaining exactly 1 foot apart at all speed steps, it’s not really necessary to get good consist performance. Whent he locos all take up teh load of the train, it will go a long way towards evening out the pull. Close is more then good enough, it won;t fry your decoders or burn up the motors. Just because you CAN do something doesn’t mean you HAVE to - it makes it seem like DCC is so much more complicated because you ‘have’ to do all this tunign to make 2 locos run together, but you don’t.
–Randy
Thanks guys. I don’t plan to run them very fast, relative to my layout. They run pretty well now at slow to medium speed. I did a small test around the layout and they kept a decent pace. The atlas will run a little better than the athearn anyway but I was able to match them fairly close.
Thanks again.
I’m hitting my head on this - except with two P42 Genesis. I think I will need to break down this weekend, and do a speed match session of the two, clock them and match their speed tables on about five points, step 1, step 24, step 49, step 74 and step 99 so the acceleration curves are almost in sync. Just using Vmin, Vmax, and Vmid isn’t quite getting the job done - I always hear the sound of one locomotive dragging the other (or pushing)
What brand of decoder are in the locos? Remember, not all decoders support vmid and vmax.
Both are equipped with Digitrax DN163K0As, which according to the instructions, list instructions for setting them (I’d assume that means they support them?)
Are you going to try to do this speed matching with JMRI, or manually? In any case, I recommend that you set you DCC system to run the engines in 28 speed step mode, not 128. Although the decoders may support 128 speed steps, if you look at the CVs that are associated with the speed tables you’ll find that there are only 28 of them. And JMRI only sets those 28 CVs when you use the JMRI speed tables. So what I do (with JMRI) is set the speed tables for speed steps 1, 14, 21, and 28.
If your decoder supports speed tables, it probably comes with some default CV values. You should note that if you manually set only CVs 1, 14, 21, and 28, the remaining settings will remain as pre-programmed, so the loco will no way run well because as you pass through those speed points the decoder will default to the pre-programmed values. If you use JMRI, you can set the program to iterate the values between the 4 values you manually set.
Of course you can manually set all 28 CVs if you have the patience.
Well, my plan of attack with this was probably going to go like this:
I figure a listing of the track used to build the current test track (lengths, mostly), stopwatch, and spreadsheet will help me come up with a viable test setup.
Am I missing some important step with this plan, or is there an easier way to this?
Yes, I think you are missing something. I’m not sure which DCC system you are using, but when you get into JMRI you’ll find that there are only 28 CVs (i.e. 28 speed steps) that you can set. That’s why I said that you should run the loco under 28 speed step control, not 128. All the 128 (or is it 126?) does is divide up the 28 speed steps into smaller pieces. But you will not find any CV for speed step 100.
Rather than set your top speed at speed step 100, use the full range of your control (1 to 28), but use JMRI to set, or limit, your top speed to what you want. I’m doing a bunch of locos for a friend, and he wants his top speed to be 60 smph. So speed step 28 should equate to 60 smph.
Once you set the top speed, run the loco in reverse and see if the speed is the same. There is normally a CV that you can adjust to make the speeds about the same. In JMRI they normally show the trim adjustments on the speed table tab.
Once I’ve got the top speed about where
One other thing to consider when running locos in a consist: Both of them should have the same momentum settings.
FOr setting the speed with CV2,5, and 6, you really only need to operate them at three settings. Speed step 1, adjust CV2 so they both run the same - one that jumps can’t be made any slower of CV2 is already 1, so you have to speed up the slower unit to match.
At full throttle, adjust CV5. You cna;t make the slower one faster if CV5 is already at 255 (or 0), so you have to slow down the faster one.
At half throttle, adjust CV6 on one of them to match the other. Either speed up the mid speed of the slower one, or slow down the faster one.
That’s all you need to do - just because they have the same decoder does not mean the values used for CV2,5, and 6 will be the same. Even with the same brand and model locos.
–Randy