Website: http://bobfrey.auclair.com
It's usual to do a full reset on a new decoder before proceeding to programming, to try and avoid issues like this. Most all modern decoders have a reset process, for Digitrax you set CV8=8 (it never reads back - CV8 is technically a read-only CV for the manufacturer ID). On a fresh install, first do the reset, then proceed to assign an address and configure what else you want to set.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Digitrax has manuals for all their decoders. Look for them in the download secton of their website, there s a LOT of good info there. TCS has a downloadable programing guide on their website.
There are CVs on TCS decoders that allow you to tweak slower and faster speeds so they run smooth together. I would assume Digitrax has simaler CVs with their decoders but cannot say for certian.
While reviewing the CV print out (via JMRI) for each of these four locos I've discovered a lot of CVs don't match (different for each loco). Many of these have to do with "locomotion", CV's 64-93.
Do these get changed "automatically" when I changed other CV's like CV2, 55, 56 & 57?
Digitrax shows default CV of 00 for most of these. Like I said, I reset all the decoders to to factory defaults before starting this. And I certainly did not change CV64-93 independently myself.
BMMECNYC Furthering Randy's comment, I read a story (cannot remember where) about how manufacturers of locomotives had issues with people putting the incorrect gear ratios into locomotives (basically the person on the assembly line in China reached into the wrong box, or the wrong box of gears was placed in front of that person). I do not believe this has happened recently, but you may find older locomotives from the same production run that have different gears. If one runs slower on DC, this could be your issue.
Furthering Randy's comment,
I read a story (cannot remember where) about how manufacturers of locomotives had issues with people putting the incorrect gear ratios into locomotives (basically the person on the assembly line in China reached into the wrong box, or the wrong box of gears was placed in front of that person). I do not believe this has happened recently, but you may find older locomotives from the same production run that have different gears. If one runs slower on DC, this could be your issue.
That had crossed my mind. One of the locos I bought used, probably 6 or 7 years ago. Two were purchased used more recently and the fourth was new (NOS, I guess BLI stopped making Blueline 10+ years ago).
rrinker Arto Another question, related to my Back EMF post. "IF" for instance, I have four "identical" locos (same manufacturer, basically the same models other than road#), all with the same decoders, am I to expect that the same CV settings on each loco will produce the same result? Or do I have to tweak the CV's for each so that the startup & speed match in actual operation? MAYBE - if the locos are the same brand, same model, and have the same decoder. But even then it's not guaranteed. The manufacturing tolerances for model locos are not all that tight. It's definitely a good starting point for a group of identical models, and in most cases will be close enough, assuming they are all broken in and properly lubricated. If three of them have a 100 hours of run time and the other is fresh out of the box - that new one is going to be stiffer than the ones that have had plenty of run time. --Randy
Arto Another question, related to my Back EMF post. "IF" for instance, I have four "identical" locos (same manufacturer, basically the same models other than road#), all with the same decoders, am I to expect that the same CV settings on each loco will produce the same result? Or do I have to tweak the CV's for each so that the startup & speed match in actual operation?
Another question, related to my Back EMF post.
"IF" for instance, I have four "identical" locos (same manufacturer, basically the same models other than road#), all with the same decoders, am I to expect that the same CV settings on each loco will produce the same result? Or do I have to tweak the CV's for each so that the startup & speed match in actual operation?
MAYBE - if the locos are the same brand, same model, and have the same decoder. But even then it's not guaranteed. The manufacturing tolerances for model locos are not all that tight. It's definitely a good starting point for a group of identical models, and in most cases will be close enough, assuming they are all broken in and properly lubricated. If three of them have a 100 hours of run time and the other is fresh out of the box - that new one is going to be stiffer than the ones that have had plenty of run time.
jrbernier IIRC, BEMF gets disabled when units are consisted to prevent them from 'fighting' with each other. I am not sure if this decoder or system specific.
IIRC, BEMF gets disabled when units are consisted to prevent them from 'fighting' with each other. I am not sure if this decoder or system specific.
It's both - Digitrax decoders have different BEMF settings for solo and consist - but importantly, the consist setting are for use with CV19 consisting, which Digtrax systems do not do by default, but NCE does. This is why there are often reports of lococ running great by themselves but as soon as they are consisted, the run horribly - because they are in a CV19 consist and the default values in the decoders completely shut off BEMF.
Does it need to be shut off? IMP no - at the club the only consisting we allow is setting all units to the same address. As such they locos are effectively runnign solo, even if 4 of them move at the same time. I don;t have any Digitrax decoders in any of mine, but I often consist a pair of locos with TCS motor decoders with another that has a QSI or Loksound decoder with BEMF and they do not fight each other. I believe the idea that locos with BEMF fight each other came from two causes - one, locos with lots os slop in the drive train, where the whole armature, universals, drive shaft, and worm in you typical diesel drive could shift fore and aft and bind the bearings in the truck towers (happens with BB and P2K locos among others - but it ALSO happens on grades when the loco runs solo and had a BEMF decoder) and by decoders with excessive BEMF levels, or that implement the "cruise control" type of BEMF where the loco will go a set speed for a given speed step no matter how mucy cars its pulling or if it's going up or down grade. Mix that loco in with one that has more reasonable BEMF designed mostly to support low speed running and there will almost certainly be some bucking action.
This article offers some more speed matching, including some insight on BEMF related to consisting:
https://tonystrains.com/locomotive-speed-matching-made-easy/
Paul
Modeling HO with a transition era UP bent
Modeling BNSF and Milwaukee Road in SW Wisconsin
First, many will advise that locos do not have to be perfectly speed matched to run in consist together quite well Having said that...
a) I suggest to run the BEMF adjustment for each loco independently; i.e., you may find the settings for "identical" locos are different enough to make them run better
b) BTW, do BEMF adjustments and consisting speed matching with broken in, warmed up locos
c) for consisting, I would suggest reading some of the available guides found on the web. It's pretty basic if the decoders utilize CVs 2 (slow), 5 (max) and 6 (mid speed). Turn off the momentum and set CV2 for the slower one at speed step 1 to speed it up to the faster one (which won't run well any slower). Then match them at top speed step (126) using CV5. I usually slow one to the max speed I want for that type loco, then run them apart a couple feet and adjust the 2nd one's CV5 to match the lead loco. Then I set both locos speed step to 63 and adjust CV6, first to get the mid speed I want on the primary loco, then adjust the 2nd loco to match. They should then run together ok, unless the decoder type is one where BEMFs get into a fight. There are articles on which decoders might fight when consisted. I haven't had to turn off BEMF on mine, most of which are LokSound Selects. So you may get by with just copying the same CV settings to similar mates, but I'd at least try the speed matching for noting how different they might be (because of drive train efficiency differences, etc).
d) also, when speed matching locos to be consisted, arrange each loco's direction (some may be in reverse; e.g., an A-A consist) the way they will be run together.