My layout is fully automated, once a train leaves 242nd Street, it does not need my attention again until it returns 18 minutes later. Given This, I turned my attention to the tower, after all that 1:1 guy does need something to do. And so I researched interlocking machines. A rail-friend send me an actual GRS lever (and some US&S levers) and I took it from there.
A *real* model builder would have cast new handles using the real one as a mold. Perhaps they could make it of aluminum or maybe resin of some sort. Even I could do it since we have a small forge in the garage basement, but LIONS were never known for patience, and so simply used brute force to shape 2" rounds (lumber sold as hand rails worked the best) in our carpentry shop.
---Notice the two motors on the sander. The original motor, the red one, was (is?) a DC motor leftover from the days when we ran our own generators, (indeed provided electricity to the entire town). To convert our machines to AC, we simply mounted an AC motor on top of the old one and disconnected the wires from the DC field. ---
On this machine there are three major parts, the first is the lever bed. You can see an interlocking dog below, that will prohibit two adjacent levers from being pulled at the same time. On the GRS machine a bed of vertical and horizontal levers provides the interlocking logic.
Lever handles alternate up and down for no other reason than to keep the operator from mashing his knuckles on the adjacent handles. A lever could control more than one switch, in that case the next space on the GRS machine would be blank since it still needs the mechanical devices for that turnout. I did not bother with this detail since I needed to put as many levers as I could in the space that I had available.
Since I use tortoise switch machines these simple spst micro switches were sufficient to manage console indicators, switch machines and wayside signals.The second level of the machine contains the electronics. On the lect can be seen -12vdc (green); +12vdc (red); and ground (white). It is necessary that the ground wire actually be grounded and not left as a floating neutral as that would allow stray current to pull or hold relays that should be released. Each lever gets one single output wire (I call it the "stinger") that will control the switches, relays and signals out on the layout. These are all shown as black wires.
Finally, there is the indicator panel. A GRS machine would have single lamps mounted in a square box above the levers. I have follows US&S practice of having two round lamps, simply because 1) I like the round lamps, and 2) it is easier to drill round holes than square ones. However, my modular design allows me to swap out the indicators without any difficulty what so ever.
Here is a GRS model 5 interlocking plant on NYCT at the Court Street Station, now part of the Transit Museum. While visitors can come in and see the machine, it is fully live and active and controls the tracks in and out of the Court Street Station. The model board is on the wall above the machine, It shows the Hoyt-Schermahorn station as well as the court street station even though this machine controls nothing outside of court street. I seem to remember a much larger machine in this location, but I am told that my imagination is unreliable. The levers to the right and left control signals the two levers in the middle control switch machines.
On my finished machine I mounted the model board directly on the machine since I had no place else to put it. Since I cannot afford 300 track detectors, it does not display the locations of trains, but rather is used as part of my automated operation system. But that is a whole different story.