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Fitting DCC Decoders to a Twin Motor All-Wheel Drive DCC Not Ready Locomotive

Poorna asks:

“I intend to buy some DC HO scale twin motor drive DCC not ready large locomotives and fix them with DCC decoders. My choices are Athearn Genesis DDA 40X Union Pacific centennials, EMD DD 35 B (Alco or Overland) with the objective of gaining the skill of fixing the locos with DCC decodes. As I’ve heard those double motor-driven locomotives need two DCC decodes. All I need to know is:
1. Is it true that such locomotives need two decoders instead of one?
2. If two decoders are fixed, how are the cables of them connected to the motors and circuitry of the locomotive?
3. Which one of those two decoders will be the primary?
and
4. How can I assign an address to such a locomotive after DCC decoders are fixed?”

Post (and view) answers below.

3 Responses to Fitting DCC Decoders to a Twin Motor All-Wheel Drive DCC Not Ready Locomotive

  • geoffsays:

    I don’t have experience of this, but I can’t see why you would need two decoders. You will need to make sure the decoder you get can handle the current draw of the two motors (might need to be an O scale decoder), and that your DCC system has a big enough power output to handle it.

    Perhaps someone else can suggest how to measure the current draw?

  • Jay Rosssays:

    I have two locomotives with two motors each. I used only one decoder in each loco. I wired the motors in Parallel, and they work just fine. The key is, you need to know what kind of current your two motors will draw, and if your decoder can handle that current. Both of my locos mentioned, have can motors that draw light current, and they don’t overload the decoder. If you were to use older, open-frame motors, chances are that it would overload the decoder because those types of motors require too much current. If a can motor draws 1/2 amp, two in parallel would be 1 amp total. Most decoders can handle that with ease. If you were to wire those two 1/2 amp can motors in series, they would only draw 1/2 amp total. However, if wired in series, they will not run efficiently, I would not recommend it.

  • Frank Bsays:

    Measure the motor’s static resistance with a multimeter. For example, it may be 6 ohms. If the supply is 12 volts, the maximum motor stall current will be (I = V/R) 2 amps. So two motors in parallel would draw 4 amps. Then you would need a 4 amp DCC decoder for that loco.

    I recommend that every model railroader should study up on basic electricity, even your school physics textbook will give you a good start. Basic books on model railroading usually cover this also.

    I suggest you buy a basic book on DCC control, which will probably answer most of your questions.

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