Problem MUing two Bachmann 2-8-0's

[tomgschilling]

I have two of the newer Connies that come with DCC installed.  I'd like to MU them but one has a top speed of 70 mph and the other tops out at approx 48.  I've messed around with CV 2 and, regardless of the setting, the top speeds seem to change very little.  I'm assuming this is a 2 function decoder and has no speed table.  Other that installing new decoders, is there anything else I can do.  Thanks.                                ....Tom

[skipgear]

I would look for a mechanical issue. Sound like maybe a bind in the motor or worm gear. How do they run at lower speeds? Is it a miss match across the board or just at top speed?

[poliss]

CV5 controls maximum speed, not CV2.

[tomgschilling]

Thanks guys;

Skipgear, both the locos run smoothly.  Their startup speed occurs at speed step 6 on my system but after that one loco slowly pulls away from the other.  The gap widens all the way to the top speed.  If it is a mechanical problem, other than lubrication, the gap increase is so constant, I wouldn't know where to begin looking for the problem.

Poliss, using Decoder Pro, it makes no difference whether the factory installed decoders are two function or four function.  Both versions have neither CV 5 or CV6.  The four function has a speed table and that would solve my problem but I doubt they put a four function decoder in the 2-8-0.                   ....Tom

[Ken G Price]

The four function does not mean CV's. It is for attaching lights, such as, ditch, beacon etc.

[Country Joe]

They just might need some running time to break in, Tom. All engines run better after break in, but steamers seem to need more running time to reach peak performance. I'm not sure if this will solve the problem, but it might.

[poliss]

Use the 'Read type from Decoder' function of Decoder Pro to find out what model the decoder is, and using that information find out if the decoder supports CV5. If it doesn't then you won't be able to alter the maximum speed.
If you're not altering CVs with Decoder Pro why did you say you've 'messed around' with CV2?

[tomgschilling]

Hi, Poliss. 

I do use "Read type from Decoder" function.  The read function results in the following:
                                         Bachmann Trains
                                                   E-Z Command Decoders
                                                       2 function Decoders (36-552)
                                                       1 function Decoder (36-551)
                                                       4 function Decoder (36-550)
The E-Z Command line, 2 function Decoders and 4 function Decoders are all highlighted in blue and the message at the bottom of the display says that multiple decoders fit the search and I must select the family manually.  The only choice that produces a Speed Table is the 4 function decoder.  If I go to the Speed table page in Decoder Pro and "read the entire page," all entries read 255.  That's why I assume my decoder is not a four function.   The Speed Table choice is grayed out if the 2 function decoder is selected.  No matter which decoder choice is made, clicking on the CV tab shows the list of active CV's and none of the decoder types have a CV 5 or 6 showing.  Therefore, CV 2 is the only CV that can be changed for speed settings.  I figured that if you altered starting voltage with CV 2 there must be some kind of firmware algorithm that establishes min, med, and max speeds.  I guess I was wrong.

Altering CV 2 by programming on the main, using my NCE system, is much more convenient and quicker than using Decoder Pro so I program on the main to "mess around" with CV 2.

Have I made any wrong assumptions given the above or taken any wrong steps.  If so, let me know.  Thanks for your help.

And, Ken, I know the numeric function specified applies to Light and other options.  It just turns out that the four function decoder, as mentioned above, also makes the Speed Table capability available for speed modification at different speed steps.

Country Joe, both locos have been broken in.                                                                 ....Tom

[railtwister]

My Consolidations have dummy couplers in front. Without a working coupler, I'm not sure how you can double head them. You may need to replace the decoders in order to speed match them...

Bill in FtL

[skipgear]

There is only one Bachmann N scale decoder. Even though they may be in different form factors (stand alone decoder, light board, tender board) they are based on the same chip and have no speed tables and very limited speed control options. You only have CV2, 3, and 4, to play with. No max or mid speed settings.

I am assuming they come like all the other Bachmann decoders with CV2 bumped up. Try setting CV2 = 0 and then see what speed step they start and if the slow one has a limp or tight spot.

The suggestion above is a good one, let them run for a couple hours then revisit the problem. It will take a couple hours for the locos to fully break in and then check speeds again. It could be the difference in brushes in the motor seated or not, valve gear dragging, etc.

[poliss]

255 is an error message saying the CV can't be read, which I would suggest in this case that the decoder doesn't support CVs 5 and 6.
Without CV5 the maximum speed can't be altered. There is no algorithm as it's a hardware problem.
Sounds like a mechanical problem. I'd take it back to the shop for a replacement.

[tomgschilling]

Thanks again, guys.  I'm going to take the slow loco apart, Skipgear.  Maybe I'll find the problem.  I ain't got a good track record when I try this sort of thing.  Usually, everything looks Okay to me (old eyes, maybe?).

Bill, I changed out the couplers to Z scale MTL couplers.                                     ....Tom

[tweetsieengineer]

My experience double and triple heading 2-8-0's has been a learning curve.  None of my 7 2-8-0's run the same.  Some naturally faster than others.  So my solution was....to simply make sure the same decoder type is in each engine.  Then set the CV's all the same on every engine.  I use the digitrax DZ125 decoder and they run great together.