MUing Locos, DCC, and Wires

Discussion in 'Getting Started' started by Gary S., Sep 15, 2007.

  1. Gary S.

    Gary S. Senior Member

    I have a couple of locos that are pretty much going to be permanently MUed together. I am considering running wires between the two locos so that each one was receiving power from every truck. To me, this sounds like a good idea and would certainly help the trains run better on less than pristinely cleaned track.

    Anyone ever done this? Any thoughts? Pluses? Minuses?

    Anyone know of any tiny little wire connectors that could be used so the locos could be disconnected from each other easily?
  2. steamhead

    steamhead Active Member

    Hi Gary...The only benefit I can see from this is (as you correctly note) to minimize dirty track related problems. Since it seems you're operating DCC, I'd just MU them with DCC and avoid the hassle of hard-wiring them together, and you can use them as single units if need be. So, just keep your track clean...You'll be doing your other engines (and yourself) a favor...

    BTW, I see you've been working hard to get your layout ready for the open house. Keep up the good work..!! :thumb:
  3. doctorwayne

    doctorwayne Active Member

    Gary, that's probably a good idea for DC, and I can't see why it shouldn't work for DCC too, especially if you can run both locos from the same decoder. Whether that's possible or not, I found some fairly small connectors at an electronics supply warehouse. They come separately as male or female, and in blocks that can be cut with a utility knife. They come in a multitude of widths, starting at 6 pins and up to 12 or more. The male plugs have a connection prong protruding front and rear, while the female has one only at the rear, and these can be trimmed to shorten the length even more. I use them for the electrical connection between steam locos and their tenders.

  4. Gary S.

    Gary S. Senior Member

    Wayne, could you post a photo of the connectors? I have two CF7s that I think I am going to tie together. Since my layout is in my garage, I may have track that is slightly dirtier/dustier than most folks, assuming that I don't clean it all the time. The MUed CF7s wired together may be just the ticket.

    I plan to use the decoders that I already installed in each loco, in other words, each loco will have its own decoder. That way I can play with the CVs individually so that each loco runs very close speedwise.... even though the locos are both Athearns, there is a bit of difference in their starting/running speeds.
  5. doctorwayne

    doctorwayne Active Member

    Here ya go, Gary!

    Both the male and the female parts come in a long strip, as shown - various lengths are available. I use a utility knife to cut them through, at the grooves, into whatever configuration I require.

    Here's a typical installation, between the loco and tender of one of my modified Athearn Mikes. There's lots of room to cram the plugs and excess wire into the tender, so I didn't bother to shorten the pins. I used some insulation stripped from some slightly larger wire to insulated the connections. I also drilled a very shallow depression into one side of each connector, then added a touch of red paint, as an identifier, so that the plug gets put together properly.


    This shot is just to give you a better sense of scale. You can trim the pins as short as you're capable of soldering a wire to, by the way.

    For using these between diesels, I'd suggest using two single-pin plugs, with the female components mounted right into the end plate of the pilot. The male plugs, shortened (ouch!) could be mounted on their wires, similarily protruding from holes in the pilot. The pins are almost square in cross-section, and I used a file to slightly round the corners. This made them fairly easy to plug or unplugged without affecting the connection.
    It may not be of much help, but the label on the female plugs reads:

    then a upc symbol,
    16 1596

    On the male plugs, the label reads:

    SIPHDR 2.5mm 2P BRST 3/6 TN
    with a upc symbol here

  6. zachary

    zachary Member

    wanye were did you buy these connetors at
  7. doctorwayne

    doctorwayne Active Member

    Zachary, I bought them at Sayal Electronics, on Harvester Road, in Burlington Ontario.
    I can't find the same part numbers on their website, nor are there pictures, and the cryptic info with the part number list is all Greek to me.
    I had gone to their store to look around, and just happened to come across the connectors that you see. On their website, I looked under connectors, and got a long list of items to click to instigate further searches. I finally found some similar part numbers under the word "SIP", from the long list.

    Here's a link, if you'd like to investigate further:

    Sayal Electronics

  8. woodone

    woodone Member

    If you are running DCC, I see no need for the wires. It would be better to install two decoders, one in each locomotive. More than likely the two locos would not run the same speed anyway. You need to set the CVs so the speed is the same on both units. Also if you use just one decoder and wire to the second unit, would you not exceed the amp rating of the decoder? Once you let the smoke out of a decoder they never work again.:curse:
    I reread your post, are you going to just use the pickup wires and tie the two units together, at the pickup connections?
    If not how are you going to hook up the two decoders together? Looks like trouble to me, if you hook up the decoders outputs together. Most have some type of EMF feed back, with the two tied together if would seam to me they would get the EMF mixed up and not work correctly.
  9. Gary S.

    Gary S. Senior Member

    Doc, thanks for the photos. There's a large electronics supply/surplus store in Houston, I'll check that out. If they don't have them or something similar, I'll research on the net. If I find them, I'll be very very careful when shortening the male ends.:oops:

    Woodone, my plan is to tie the pick-up wires from each loco together. The decoders would be left seperate on the motors. So, red to red, black to black, but that is all. This way, each loco/decoder is picking up power from four trucks instead of just two, which is eight wheels which is even more than some big ol' AC4400 something-or-other six axle loco! Out of 8 wheels on each rail, you would think at least one on each side would be making good contact.

    Now, another modification would be to solder wires to the brass axle bearings up to the truck internal sideframes and then from the sideframes up to the red and black wires... to do away with two more point of less-than-secure electrical contact.
  10. woodone

    woodone Member

    Well that sounds good to me. You would have all the wheels picking up over a very wide wheel base. Should work out fine.
    I was just afraid that your were trying to hook the two together and only use one decoder. Good luck, let us know how it works out.
  11. Russ Bellinis

    Russ Bellinis Active Member

    Gary, I think it would work, but you would be restricted to always runnig the locomotives in the same position in relation to each other-ie. either front to back with the low hoods pointing in opposite directions or elephant style. Since all 8 wheels are wired as one locomotive, you will have in effect a single articulated locomotive with separated decoders for each section. I think you would lose the ability to make many of the cv adjustments that would be available to you if the locomotives are kept separate, but I don't know for sure.

    I also noted in a post farther down this thread that you mentioned soldering the bearings to the trucks and then hard soldering the truck sides to the motor. I'm presuming the Cf7s are Athearn models. If so, the bearings are designed to float to allow for a certain amount of "suspension movement" to compensate for track irregularities. I think if you solder the bearings, you may run into derailment problems with the locomotives. I've posted this link in other threads, but this is a sytem that works for Athearn and other brands that use a similar drive. The picture is for dc, to use this system for dcc, you just run the wires from the truck sides to the decoder and then from the decoder to the motor per decoder manufacturer's instructions.

    Five Wire System
  12. Gary S.

    Gary S. Senior Member

    Russ, when I say "solder the bearings" I am talking about using decoder wire soldered on the bottom of each bearing, then that runs up to the sideframe. This leaves the bearings free to float just like they did originally. From there, we will use the "five-wire" system to the decoder.

    Alternatively, the bearing wires could go directly to the decoder similar to the five wire system.

    I've already done this on a GP-38 and it works great.
  13. Russ Bellinis

    Russ Bellinis Active Member

    Ok, I misunderstood. Are you also using a short piece of decoder wire to connect the bottom of both bearings together before soldering them to the decoder in the 5 wire system?
  14. jbaakko

    jbaakko Active Member

    I could see it working. You should be able to consist the decoders, under one address. The wiring should not be too much more complex, just some splicing. Might I suggest dummy couplers between the units though, to save $$.
  15. Gary S.

    Gary S. Senior Member

    I did the GP-38 like this. I could have skipped hitting the sideframe and taken the bearing wires directly to the decoder.

    Attached Files:

  16. Gary S.

    Gary S. Senior Member

    And not necessarily to just save money. On occasion, I have had unwanted uncoupling when running over uncoupling magnets at slow speeds due to speed mismatch. But still, there needs to be a way to take the locos apart when I need to.

    Oh! Cut the pins off the Kadee couplers between the locos! Doh!
  17. Gary S.

    Gary S. Senior Member

    One more thing for the record. I think I remember reading about doing the bearings this way. Don't remember the source if there is one, it is possible I dreamt the whole thing? Anyway, I don't think this is my idea.
  18. Gary S.

    Gary S. Senior Member

    Additional note for Russ:

    Sinci my layout is a point-to-point, I would MU the locos "back-to-back" = long hoods together so that I don't have to come back "backwards" if that matters...
  19. Russ Bellinis

    Russ Bellinis Active Member

    I don't know if they are still available, but MDC Roundhouse used to offer dummy couplers in each kit with the horn hooks. They are precisely scale dummy couplers that can be hooked together sliding one knuckle down over the other one to make the "hands" clasp. I used them to draw bar an a-b-b-a set of Stewart ft's, and they worked great. Since they are cast in plastic, there are no electrical issues when using them to connect 2 frames together.
  20. Gary S.

    Gary S. Senior Member

    Follow-up on this project. Finally got it working to perfection tonight. Got the two locos matched for speed characteristics by adjusting the CVs, figured out the best routing for the wires to avoid binding the trucks or interfering with the mechanism, found some small wire conectors, and got it going after quite a bit of experimentation and reworking. The brass bearings have wires soldered to them and up to the circuit board which eliminates some of the "contact pressure" connections from the trucks to the circuit board. I ran them for awhile tonight, pulled some cars, did some magnetic uncoupling, I'm real happy with it now.

    Essentially, my 2 CF-7s are MUed together and share all the wheels in picking up power for each loco. Yep, each loco is getting power from 8 different wheels per side. These are the CF-7s that I weighted with lead inside the bodies awhile back. So, now I have one bad-boy MU consist with good power pick-up that eats dirty track for lunch, no flickering lights, even when traveling over Atlas #4 turnouts, and these babies gots some mucho power!!!

    Here's a diagram. I used black wire, shown in red for clarity.

    Attached Files:

    • mu.jpg
      File size:
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