Thursday, August 11, 2011

Breakin' the Rules

One of our first lessons in Model Railroad Kindergarten is usually "make sure you can maintain it." Make sure hidden track is accessible, don't glue coupler boxes together, and use terminal strips so you can easily test and replace wiring on the layout.

When I was a teenager, I followed the wiring rule pretty religiously. Because I was having fun experimenting with electronics, I think I ended up spending more of my hobby budget on terminal strips at Radio Shack than on model railroad supplies. When I started the Vasona Branch, I knew I needed to do something different, both to avoid the long runs of wire to reach those terminal strips and avoid the cost of making things maintainable.

Many model railroaders suggest running DCC wiring with a pair of heavy (12-14 gauge) bus wires near the tracks, then running smaller wires from the buses to the rail. Sandwich connectors ("insulation displacement connectors") make the connections to the bus easy, requiring only crimping with a pair of channel lock pliers. Occasionally (once a year) a connector might fail; wiggling a wire or re-crimping solves the problem quickly, and it's usually easy to diagnose the problem.

The sandwich connectors worked very well on the DCC wiring - there was less wire under the layout, and wiring everything up went quickly. When I gave up on hand-thrown switches and converted to Tortoise switch machines, I'd gotten used to the idea of not having terminal strips around the layout. I also realized I didn't want to do lots of soldering under the layout, so I started doing more of the work at the workbench.

Here's a photo of a typical switch machine being prepared for installation. The Tortoise sits under the layout near the switch; the toggle switch is inset into a plastic pipe end cap that is placed flush on the layout fascia so the switch can't be bumped. All the wiring from the switch machine to the switch and the wires to the supply are soldered at the workbench. I solder the "x" needed for a reversing DPDT switch by stripping the end of a wire, then using the strippers to pull insulation from another point a couple inches down. The tip of the wire gets soldered to one terminal, and the gap further in goes to the terminal that's on the opposite side of the switch.

While at the workbench, I also open the Tortoise up and grind away some of the copper for the contacts powering the frog; all my switches are Shinohara, and the points don't always move fast enough to break away from the supply rail. With the as-bought contacts, I'll sometimes get shorts depending on how the switch machine's linked to the points.

When I'm ready to install the switch, I drill the holes to mount the switch machine, bore the hole for the plastic pipe end cap using an adjustable spade bit, secure everything in place, then use sandwich connectors to connect the toggle switch to the switch machine bus power. The extra yellow, black, and red wires are for frog power; the yellow wire goes to the frog, and the black and red go to the DCC bus. I'll usually figure out which wire goes where by using alligator clips to temporarily power the frogs from nearby rails, then figure out which bus wire corresponded to which rail.

(One helpful hint for wiring: with DCC and sound, leave the layout on as you wire up new sections. If all your locomotives go quiet, then you've miswired something.)

With all this screwed into place, maintenance might seem to be a problem, but I've found there's enough slack to unscrew the switch machine and check out problems under the workbench. For serious problems, I can cut wires, check everything at the bench, and re-crimp the wires in place afterwards. I'll have to mess with a switch machine on the layout a few times a year, and so far this hasn't been too onerous. I do make sure there's enough slack wire in the line to get the switch machine out.

All this might not be the *right* way to wire a layout, but for a smaller layout like mine, it's worked just fine.

And if you're curious why I'm messing with switch machines and switches: this switch machine's going to be used for a new team track at Campbell. That's a story for another day.

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