Posted by: bgtwindad | August 31, 2014

Con-Cor / Rivarossi N Scale 4-6-2 “Pacific” Decoder Install (Part 2)

In Part 2 of this install, we’ll explore the trickiest problem involved in this install:  connecting power from the tender to the locomotive.

Older versions of the Rivarossi 4-6-2 used a plastic drawbar, and only the little spring wire pressing against the drawbar pin in the locomotive to transfer power.  For a DC locomotive, this turned out to be a fairly poor design, but for a DCC install, it makes isolating the tender from the motor pickups easy.

(Un)fortunately, this version of the model uses a metal drawbar, which is much better for ensuring good power transfer under DC, but makes it much trickier to isolate the tender from the motor.

A few options that either I considered or were suggested, which I rejected (and the reasons why):

  • Enlarge the hole in the loco end of the drawbar and put shrink wrap over the drawbar pin.  I was concerned about friction and wear on the shrink wrap, so no.
  • Replace the drawbar with a plastic one.  This would have been an excellent option if I could have disassembled the pin at the tender end.  I couldn’t figure out how without destroying it.
  • Insulate the axle wipers from the bar rivets and wire directly to them.  Again, I was concerned about wear, and I just didn’t have the parts.

In the end, the simplest solution seemed to be to cut the brass bar.  It would have been much easier if I could have removed it from the tender first, but it’s riveted in place, so no.  Instead, I used a drill press to drill up from the bottom where there’s an opening in the plastic, and then cut the rest of the way through the bar with a Dremel tool and a reamer bit.  I did a somewhat messy job of it, but it worked.

Here’s a view of the bottom of the tender before the cut. You can see the opening where I made the cut on the left.
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Once the cutting was done, I soldered a piece of wire to the bar in the middle of the tender and routed it through the hole to the front near the drawbar. At the drawbar end of the wire, I attached one pin of a NEM651 female connector and shrink-wrapped the connection.

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Finally, I finished the end of the wire coming from the loco with a single pin of a NEM651 male connector. At that point, we’re done except for buttoning things up and testing her out.

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I found when testing that with the female socket secured to the tender, it was very difficult to connect up the locomotive on the track. The quarters are very tight between the cab and tender, and I had cut the loco wire just a tad short. By leaving the plug loose, I was able to bring it out of the tender enough that the wires can be connected before the drawbar is hooked up. Much easier, and with everything being black it still looks OK. We’ll see what the customer thinks. I hope he likes it.

 

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