I have to start out with if you don't have a Digitrax PR 3 and JMRI Decoder Pro you don't know what you are missing!
Few months ago Simon 1966 speed matched 3 of my 4 PK 2000 F-3 Monon's. Two are A's and two are B's. Using decoder pro I copied the CV's from the B that was speed matched to the new decoder in the B that did not have a decoder at the time. They work perfect with each other, and I know it was just pure luck that it worked out that way.
One of the A's gave Simon fits with CV 6 mid speed. It all so stopped running well with the other F-3's. It is ran as the rear engine of the 4 engine consist. Tonight I speed matched it to one of the B's and added it to the 4 engine consist. Great news is the engines are not fighting each other, no racket from slipping wheels. I am pulling a 55 car train.
Only small problem is the front engine is jerking back and forth just a tad. Coupler gets slack then tight. In DC you want the harder pulling engine in front, I am guessing it should be the same in DCC. So a little more power to CV 6?
Thanks for your time, Cuda Ken
I hate Rust
Sounds like they are about as speed matched as they could possibly be, if the second unit 'catches up' a bit if the lead unit stalls at all. Try flipping the whole consist around and see if the former trailing unit now always pulls or if the same slack action occurs. Yeah it'll look wierd with a B in front, but this is just to test the matching. Couple it to a train like you were running it, not just the two units alone. If the behavior changes, then yeah, add one or two to CV6 on the A to make it a touch faster.
Now the more complex part. Are any of the decoders in either unit BEMF capable? If either one is a Digitrax 163 series (not 123's), make sure it is set to turn BEMF off when in consist. It's one of those complicated CVs where 'half' is standalone and 'half' is consist - however this is what DecoderPro is for. Actually, I take that back, DecoderPro doesn't actually show that in plain English. It's CV57, and if it's 16 or less, BEMF is off when consisted. But only ADVANCED consists using CV19 - using the default UniVersal consisting, this doesn't apply, and the loco will use whatever level of BEMF CV57 is set for, from 0 for off to 16 for max. So if you have a DH163 series decoder in either one, try reducing CV57 to 5 or less. If another brand of decoder with BEMF, check to see if there's a way to reduce or turn off BEMF when the loco is in a consist.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I had a very similar problem with a pair of Proto GP9s. They seemed to run pretty well together, but I noticed one of them was occasionally stalling briefly. Since this seemed to happen most often when running over an Atlas Customline turnout, I figured I had a bad connection between the wheels of one truck and the decoder, since most of the time it was running fine, but I only had problems when the good truck was passing over a dead zone.
Turns out it was a loose wire. A touch of the soldering iron brought it back to normal.
It takes an iron man to play with a toy iron horse.
Thanks for the answer folks. Randy, finally something the DH 123 decoders are good for! All 4 have DH 123's. I pulled the lead engine and the rest ran fine with each other, in fact a little better. Train started moving at a slower speed.
Read the decoder on the lead engine and found its CV 6 was sat at 118. Looked at the records (I love Decoder Pro) and the B I speed match the other A to last night CV 6 was 123. Changed the led engine CV 6 to 123.
No jerking at all now!
While I was looking at speed control I saw what was called trim, and there CV's where 128. Guessing trim is the balances of power applied to the motor going forward or backward. Am I right?
Ken
Yes, the forward and reverse trim values are to asjust the whole speed table up or down to compensate for slight differences in the loco's operation in forward or reverse. Diesels are usually pretty uniform, but the law of model railroading says a steam loco will always run better in reverse. Differences are usualy due to tolerances in the gearsn and universals - think about it, if the motor turns one way, everything's loaded to one side of the gears and bearings, when it turns the other way, the loading shifts to the opposite side. The trim CVs allow you to shift the entire speed table, not just the slow speed end or the top speed end, since the variations they are intended to correct are not speed dependent. It's like adding or subtracting 5 to every value in the speed table without changing each of those individual settings
Edit: Never mind. Duplicated answer
Springfield PA