How do "Engine Consists" work?

Discussion in 'HO Scale Model Trains' started by djk, Jul 5, 2007.

  1. djk

    djk New Member

    I have a DCC layout, NCE Power cab. I set up a consist with two engines and started to wonder how it can work.

    When I run the engines separately, they go at slightly different speeds when the throttle is set at the same "speed" number. So when you build a consist,what is making the engines go at the same speed? Are they going at the same speed? Is the speed of each engine adjustable? Is the decoder in the engine sensing things or is the Powercab sending out the appropriate signals? Or is it all done with magic?

    I ask because most of the time everything runs fine, but sometimes the rear engine appears to be pushing too fast and the last car before the engine derails.

    Thanks for the info.
  2. IAIS 604

    IAIS 604 Member

    Yep - done with magic!

    If you are mage-challenged, then you must adjust the speeds of the locos by adjusting the proper CVs in the decoders until the speeds match (or get close enough).
  3. JR&Son

    JR&Son Member

    Some where I made a post, describing the Train Buddy working with a Bachman and Athern E8, over the period of about and hour he had them running consistantly to withing .5 second over a 2 level mainline about 100 feet long. He played the weakness of each engine against the other to arrive at a near perfect speed match. Looked at another way, he set them up 1 foot apart running behind one another, after 10, 20, 30, 40 laps they stayed 1 foot away from each other
    Train Buddy, Discount model railroading.  DCC install, service, repair, computers, electronics, custom builder


    By the way, according to the search feature, I have never posted...go figure.
  4. sumpter250

    sumpter250 multiscale modelbuilder

    When you create a consist, a separate address is created, that your throttle "talks"to. This "address", then talks to each of the decoder addresses in the consist, so they all respond to the same commands at the same time.
    Consisting cannot make the locos all run at the same speed. That has to be set individually, using the speed tables in each decoder. If each loco has been set up to run at a specific speed, at a specific throttle setting, ("matched"), then they will all run well together in a consist.
    If you are using a loco at the rear of the train, as a helper, you need to get it matched with the loco(locos) used at the head end, need the rear end helper on a separate throttle, so you can adjust its speed as required. I run a pair of P2K 2-8-8-2s, one at the head end, one pushing. Because they are from the same manufacturer, released in the same production run, they are basicly "matched", and I can run them in consist. I usually have them on separate throttles, so I can "whistle talk" train loco, and helper.
    You might find info on speed tables, already posted in the DCC forum. If not, you can ask there, and should get response from someone who knows more about DCC than I do.
  5. Russ Bellinis

    Russ Bellinis Active Member

    I'm sure you can get specific information about adjusting the speed tables from NCE, probably in the operator's manual that you should have gotten with your system. If you are running the consists at the head end of the train, being speed matched won't be as critical. Just put the slower of the 2 engines in the lead. The weight of the train will tend to even out the speeds anyway as both engines need to share the load to pull the train around. Where you may run into problems is if you run a pusher for helper service. If you have a long enough train, you won't have a problem with helpers, because the locomotives on the point will pull the cars in the front part of the train, and the pusher will push the cars to the back of the train, and coupler slack will help you out. The problem will occur if your track has a dirty spot. If the locomotives on the point hit a dirty spot on the track and stall, the pusher in the rear will start derailing the train.
  6. Triplex

    Triplex Active Member

    Or the other way round - tension can derail a train on a curve.
  7. IAIS 604

    IAIS 604 Member

    You need to get the CV values/settings for a speed table from the DECODER manual/instruction sheet. Your NCE system manual can then tell you how to change them to those values. Experimentation with different values within a range will be needed to get a best speed match.

    What decoders are you using ???

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