Saturday, March 19, 2011

Bending the Iron at 1/87th Scale

Toy train sets generally come with an oval of track. Manufacturers of these sets know that one of the first things beginning modelers will want to do is add variety to their budding layouts, thus the scale turnout was born. Along with these scale turnouts came the need to control them, either manually or using some powered apparatus. Solutions to this problem as diverse as the Tortoise, the twin coil switch machine, and the ground throw quickly evolved.

In addition to the above, there have been a huge number of roll-you-own solutions to the problem of "bending the iron". Examples include automotive choke cables and RC model airplane linkages. One thing that all the above have in common, though, is they cost money-in many cases, as much or more than the turnout itself, and the turnouts aren't cheap to start with. So began my quest to figure out how to control the turnouts in my basement-without spending an arm and a leg doing it.

My first attempt was using the least expensive option listed above, the Caboose Industries ground throw. In addition to cost, these have the advantage of looking something like the actual mechanism used to control a prototype switch that is thrown by hand. They are grossly overscale, though. But the big problem I found in using them was the need to sometimes reach behind cars and operate them, without being able to see them. This led to occasional derailments and general frustration during what was supposed to be an enjoyable time. So the search for a "better way" began.

Regular readers know that I'm a tightwad, so one of the requirements for whatever I came up with was that it was affordable. Second was reliability-the proper solution would apply force to the points to hold them where they were supposed to be in order to minimize derailments and electrical problems. Third, the solution needed to have the capability of being operated from the fascia, to avoid the problems posed by the ground throws. In addition to these criteria, it would also be nice if there was a way to determine the position of the points from a distance. Shouldn't be so hard, should it?

In the end, no. But I did go through some experimentation before arriving at what I think is a rather elegant solution. My first attempts at converting rotary motion to linear motion and applying the result to the points was not consistently successful, so I came up with a push rod system that worked pretty well, but could use help in holding the points in position every time, and didn't offer an easy way to indicate the route selected. Back to the drawing board. Eventually, I came up with this:

What's needed to make this work? Well, for each turnout I use about 6" of piano wire from the hardware store, a few inches of 5/16" dowel, a wooden wheel that fits the dowel, some 30# test black fishing line, a couple of scraps of wood (a few inches of 1 x 2 and a short piece of lath), an eye screw, and a few wood screws. Material cost is well under a dollar a turnout. (NOTE: the wire I use is really springy wire, not something that is easily bent. You can poke this wire through your finger! It will bleed! Be careful with it. This HAS to be really springy, "music" or "piano" wire, not any old soft wire you have. If you can bend it without really trying hard, it probaly won't work.) Tools needed include a drill bit to make a hole in the foam layout base, needle nose pliers, a coupld of small drill bits for pilot holes and holes in the dowel, a 5/16" bit, and a heavy duty wire cutter for the piano wire. Wear safety glasses when you cut it! I've also used a bit of craft paint on the dowel to indicate turnout position-green up is normal, and red up is diverging.

So how does it work? Rather than try to explain, I'll present the following video:

It took a few tries to get the hang of installing these, but once you figure out the geometry, you can move right along. I can now install one in less than an hour, from the time I decide to get out the tools until it's painted. And it is an enjoyable hour. I will warn you that when you trim the piece of the spring that protudes through the top of the throw bar, be sure to wear eye protection as cutoff segment will want to go flying.

All in all, I'm really please with the way these work. They meet all the requirements I mentioned above and the best part is, it's something I made with my own hands. I solved a problem!