I have recently purchased a Proto 2000 F7A-B set from Walthers but am having problems with consisting.
When I put the A and B units into a consist the two units seem to 'see saw' as they move. The motion is bad enough for the units to uncouple over an uncoupling magnet. I thought I could live with the problem and have just replaced the uncoupling magnets with electromagnets to stop them inadvertently uncoupling. However I am finding that with any more than four or five cars the see saw motion is transmitted down the train to such an extent that the last few cars of a longer train jerk quite badly.
I would appreciate any suggestions to remedy the problem (I am new to model railroading and DCC so would like a fairly basic explanation if possible - these are only my second and third locos).
Details of my system (in case this has anything to do with the problem) : I use a Prodigy Advance2 DCC and a PSX1 circuit breaker. The F7A and F7B are coupled with Kadee # 43 couplers not the couplers supplied by Walthers. I use the advanced consisting function to program the consist.
What decoders are in the locos? If the decoders have Back EMF or some kind of regulated throttle responce then you have to disable that function or they will fight each other going down the track. This is the most comon problem with consisting decoders.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
If these were DCC/sound equipped, they use a QSI sound decoder.
First, cancel the consisting and re-program CV 29 to turn off DC Conversion. The usual value for CV 29 should be 34, which tells the decoder to use a long address, 28/128 speed step. If CV 29 has a value of 38, DC operation is turned on and this can cause problems when running on DCC.
If that doesn't solve the problem, go to the QSI web site and download their Diesel Decoder Technical Reference Manual. I don't think the decoders in those locomotives have Back EMF, but turn it off if they do.
You'll need to query the decoder's CV 7 to see which version software it has in it, and then download the appropriate manual from QSI because there are three or four versions of the decoder and the manual.
Also, insure that CV 2, Start Voltage; CV 3, Acceleration; and CV 4, Deceleration, are set exactly the same in both decoders.
The system details you provided should have no effect on this problem.
The newer QSI decoders have the Back-EMF turned on again, now that all the silly lawsuit business is out of the way. So this is where the problem lies. No matter how well built, two locos never run 100% perfectly together - if if you can put the ont he track not coupled but say 1 foot apart and runt hem around and they stay 1 foot apart - they'll never been EXACTLY perfect at every speed and especially when starting up. So when two locos are coupled, they end up see-sawing back and forth as one tries to push a little and the other tries to pull a little. When two or more locos are consisted it is usually recommended to turn off or at least reduce BEMF so this doesn't happen. Some brands of decoders have two BEMF settings, BEMF when running alone and BEMF when in a consist. Not sure about the QSI. In any event, turning off or reducing the level of BEMF should solve this problem.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Thanks Pete, cacole and Randy for your advice.
I changed the value of CV 29 to 34 so that DC was not an option. I then turned RTC off as well. The overall locomotive performance with RTC off was worse than with it on but the seesaw motion has decreased but not stopped. I also checked CV's 2 to 4 and they are the same in both locos.
Because of the poor performance without RTC the locomotives look better running with it on but the seesaw is still happening.
The locomotives come with the QSI decoders as ordered from Walthers. These decoders have two modes - standard and RTC. The QSI manual talks about regulated throttle control (RTC) as being their choice for controlling the locos in a consist. It appears to contain some elements of BEMF as you have all described.
Are any of you able to offer more advice in reducing the seesaw motion?
Which CV did you change to turn off RTC? It's an indexed CV, to disable ALL types of speed control, you would first set CV49 to 4 and then CV56 to 0. This would turn off any compensation and they should at least stop fighting each other. Solo performance may suffer with no feedback of any sort. If you don't already have it, go to the QS Solutions web site and downlaod the full manual for the decoders.
tonis88 I have recently purchased a Proto 2000 F7A-B set from Walthers but am having problems with consisting. When I put the A and B units into a consist the two units seem to 'see saw' as they move.
When I put the A and B units into a consist the two units seem to 'see saw' as they move.
Sounds like you didn't bother to speed match them (or check if they needed it at least). You can forget all the other remedies posted here if you didn't check for speed matching.
I have had matched As & Bs out of the box (and with identical decoders installed) that ran are wildly different speeds, not to mention even differently in reverse. I have also had matched sets out ot the box that were pretty close in speed, but never identical.
Not only can they be instrinsically very different in speed, but if they are actually preowned, one can have much different cleanliness on the commutator and/or wheels that will cause variations in speed.
So before you worry about anything else, learn about speed matching from archived posts and at least give them a speed test. It is not difficult and is the first essential step in creating a consist.
You mentioned that they are new. It is the usual recommendation that you run each of them (separately, of course) for an hour or more if brand new, to get a little settled in speed-wise. A loco that is speed matched when brand new, or even one that is already speed matched, will perform much differently each time started up until it hits its broken-in & warmed up speed. I have just spend a month speed matching more than 40 sets.
Thanks David, Randy and Cisco Kid for your advice.
I had never heard of speed matching locos so I did just "shake the box to consist them" (although in my defence there is nothing in the instructions about speed matching ). I will now try speed matching the locos and see how that goes! I did break-in the locomotives (this part is in the instructions )
The A unit is faster than the B unit, and as I explained in a previous message the seesaw causes them to uncouple over an uncoupling magnet. When they do this on a loop the A unit uncouples and laps the rest of the train and attaches itself to the tail end car leaving the B unit pulling the train. The first time this happended I was not watching and was startled to see the train being pulled by the B unit with the A unit pushing.
Looking at previous posts about speed matching I will start with adjusting CV's 2,5,6 and 95 to match the train speeds.
Now you are on the right track. Using those CVs alone should do the trick. Be sure that CV 3 and CV4 are set still to 0 (the default) so that there is no difference in acceleration and deceleration rate while speed matching. These rates, which should be sort of matched too, can be done later.
Everyone has his methods. I like to get both locos set to an identical prototypical top speed first using CV 5. I do this separately for the locos. For your F units that would be 65 scale miles per hour...or travelling 3 feet in 2.7 seconds or 6 feet in 5.4 seconds. I have some 3 foot posters along one wall that are handy in helping me with this calculation.
Then I consist them and start setting the starting point CV 2 for each so that they begin crawling at the same time and then try setting the mid speed.
Your locos might not be as far off as they seem. With the B pulling a train, the loosed A unit would naturally make it around the circuit noticeably faster.
I would like to consist a couple of steamers eventually. When I see threads like this one, it puts me off. However, I do keep seeing a scrolling marguee in my brain saying, "Learn to use JMRI's Decoder Pro and get the hardware! You'll be glad you did."
-Crandell
I dunno, I never had issues consisting, but it was usually two locos from the same manufacturer. I ran two and even 3 of my GP-7's together, never had to adjust a thing and they didn't jerk back and forth. I ran two PCM T-1's (both with sound) together and they were OK as well, no adjusting needed. If you can set them like a foot apart and run them and the distance stays the same, they should run well coupled together as well.
selector I would like to consist a couple of steamers eventually. When I see threads like this one, it puts me off. However, I do keep seeing a scrolling marguee in my brain saying, "Learn to use JMRI's Decoder Pro and get the hardware! You'll be glad you did." -Crandell
Well, I found Decoder Pro to be extremely helpful and is essential if your particular decoders do not support CV2,5 and 6. This is the case with some very cheap ones like the Bachmann DCC on board Lenz 100s, but also with many more expensive decoders like QSI and Soundtraxx which require changes in speed tables to fine tune speeds.
With decoders that require speed table changes, one would have a devil of a time if the locos were typically different in speed, or were of different makes with different decoders. With Decoder Pro one can see on the panel the actual position of each speed cv slider and one can elect to create a "user" speed table that is readily visible. Without DPro one would be "shooting in the dark" while writing a series of preset tables to find the correct speed match.
I use CVs 2,5,6 whenever possible because it is easier. These can also be done simply with the command station. But anything requiring speed table adjustments of the 28 (x2 for two locos) CVs using only the command station would be slow and frustrating.
As for those who find locomotives run very closely right out of the box......that is great, but not always the case. It is certain to be not the case if the brand, or loco type or decoders are not exactly alike.
But it can be done. I have finished matching 80+ diesel locos in pairs (some triplets) and am now working on the steamers. Of course, the steamers were less likely to be run in consists because of the costs of having to have full crews in each loco cab....but it was done.
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