Q: I’m setting up a model railroad on a 6 x 12-foot table. The layout will use Digital Command Control. What would be the best wire size(s) to use on the layout? — Greg Kurtz
A: Two considerations when selecting the right wire size, Greg: First, that doesn’t involve long bus-wire lengths, so No. 14 wire will be fine for an HO scale layout. I use red-insulated wire for one bus wire, black for the other. But don’t make a continuous loop of the bus wires; run them from the command station, keeping them separated by at least 6 inches or very loosely twisted, and terminate them before they come back to the command station.
And be sure to connect No. 18 or even short No. 22 feeder wires between each rail and the corresponding bus wires. (David Popp used smaller wire for an N scale layout.) Color-code them black or red to match the bus wires to avoid mistakes. Never depend on rail joiners to carry current.
If you solder the feeder wires to the rails, be sure the rails are sparkling clean where the joint will be made. The type of solder you use is a matter of personal choice. I use a silver-bearing solder (not pure silver solder) for greater strength — same for the feeder-to-bus wire connection. However, I normally use 3M-brand ScotchLok Insulation Displacement Connectors (IDCs) for this connection and have never had a failure when properly installed. I put one IDC on the bus wire every 6 feet or so and run a short No. 18 pigtail from it. I then use a large wire nut to connect several feeders to the pig tail, thus saving on expensive IDCs.
Digital Command Control expert Mark Schutzer usually reserves silver-bearing solder for attaching points and frogs to printed-circuit-board ties where the extra strength is needed. For power drops on layouts he uses tin-lead solder. Mark further notes that 63/43 tin-lead solder has the lowest melting point of any regular solder: 63/43 melts at 173 degrees Celsius (343 degrees Fahrenheit). Silver-bearing, non-lead solders melt in the 210 to 230 degree Celsius range (410 to 450 degrees Fahrenheit). Since you don’t have to get the rails as hot with tin-lead solder, you aren’t as likely to melt the plastic ties.
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