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Decoders in older brass locos

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  • Member since
    February, 2008
  • From: O'Fallon, MO
  • 292 posts
Decoders in older brass locos
Posted by Lateral-G on Friday, February 29, 2008 12:02 PM

Any tips for installing decoders in older brass locos?

I have a HOn3 PFM/United 4-6-0 w/tender drive, I re-motored with a Sagami can motor and I have just enough room for a Digitrax N scale decoder (which will fit in the tender). I think it should be straight forward since all I have are the motor leads (no lights to worry about). It runs very, very well now and has superb low speed performance on straight DC.

I also have a HOn3 PFM/United Shay that has the original open frame motor. I seem to recall reading somewhere DCC, decoders and open frame motors aren't a good mix. Unfortunately remotoring the Shay is not something I want to do, especially since it runs very, very well. (if it ain't broke, don't fix it.....)

Thoughts?

-G- 

 

 

  • Member since
    July, 2006
  • 290 posts
Posted by steamnut on Friday, February 29, 2008 5:46 PM

While I'm not familiar with your specific loco, there are two general problems with trying to install a decoder in an open-frame-motor environment:

(1) In every open frame installation I have ever seen, the motor is electrically connected to the locomotive frame. This is an impossible situation for a decoder - the motor MUST be electrically isolated. Doing so is usually quite difficult; the motor both rests on the loco frame, and is screwed to the loco frame. Some have isolated it by replacing the metal screw with a nylon one and placing either electrical tape or very thin plastic between the motor and the loco frame. But unless your loco has a gearbox (as opposed to a simple worm) this is likely to affect the mesh between worm and gear.

(2) Current draw will also be a problem. You'll need at least a 1.5-amp decoder.

Good luck.

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