Wiring Interlockings

Interlockings, controlled locations on railroads where trains can change tracks and signals can be displayed by a dispatcher or operator, are very complicated installations. Turnouts themselves are complicated, and so is the circuitry and wiring to control the turnouts. This chaos is the underside of the staging level at both ends of the staging yard. This shows first-hand why colors are so important for organized wiring - it is the only reliable way to tell what goes where! Some of this will be cleaned up using zip-ties, and I plan on labeling most of the origins and terminals so as to provide some insight during future adjustments or electrical problems. This image shows a typical installation for a pair of the Circuitron 'Tortoise' machines. These come with a mounting jig, allowing the installer to locate the machines using a small hole drilled through the benchwork at the location of the throwbar on the turnout. Four pilot holes are drilled for mounting screws, and the machine is installed from below the subroadbed. I had to check the alignment several times in order to get the location just right, but it has worked out well so far. This is the 'heart' of one of my interlockings, CP 295. This is the 'west' end of my staging yard, and this terminal strip is how I have routed a separate power suppy to the switch machines. While I used red and white wire for track power, I have used black and green for switch power, and will someday use blue and yellow for signal power. The heavier 14-gauge green and black wires lead to another terminal strip which is the location from which all my switches will be powered, and it in turn is wired to an old transformer set to 10 volts.

The nicest part of the Tortoise machine design is that it is constantly under power, and simply will stall once the points reach their full throw. This means that the machine will not burn out from constant power, which is a nice change from the cheaper 'snap' switches I was used to.
Here is the organized chaos of the back of a model board, the 'brain' and control center for an interlocking. These are double-pole, double-throw switches that essentially reverse the DC power to the machines, which simply makes them spin one way or the other, throwing the switch. The thin orange and white wires run from the switch to the Tortoise machine. For now, these are mounted in a simple cardboard mockup of what will soon be a black plexiglas model board, with white lines representing tracks and decals for labels. I will also be installing LED's as indicator lights, although not until the final model boards are in place.
The temporary model boards for each end of the staging yard... And, finally, a close-up shot showing the throwbar itself on a Micro-Engineering #6 switch in the staging yard. If you look at the close end of the throwbar, you can just barely make out the end of the steel wire that links the machine to the throwbar and moves the point rails. It's a nice set-up and worth the extra money compared to other machines.

This completes the work on the staging level that must be done ahead of the second level! It's a major milepost in construction. This weekend, Rick & I will be installing the benchwork for the second level, and then we're back to installing roadbed, track, and more interlockings.

Stay tuned!