The plastic tube going up through the benchwork is exactly that, some plastic tube bought from the LHS. I don’t remember the exact sizes, but I think it is ½” at the bottom, and then the next two smaller sizes that fit in kind of like a telescoping tube. The two lower tubes are glued together, the upper tube is left so it can slide so fine adjustments for height can be made. The bottom of the tube doesn’t fit tightly in my foam, but the upper part is “snug”. It can be easily moved up and down and twisted to align it, but there is some friction to the fit. If I had it to do over, I might use larger size tubing because I had to file out some grooves in the bottom of the tube and in the aluminum angle iron because of the throw of the wire at the bottom.
The reason I used the tube is so there would be a pivot point for the steel “music wire” going up to the turn-out. Notice there is a plastic disk with a small hole drilled in it that the wire goes through. Now, actually, after I built some of these, I tried them without the plastic tube and pivot point, and it still worked just fine. You could probably just drill a hole up through the benchwork and not use the tube. But, since I already had some made, I just built them all the same.
One thing the pivot point does is make the pull of the knob direction be the same as the points. If I pull the knob out, the turn-out will be aligned to the front track. If I push it in, it routes to the back track. Without a pivot, it is just the opposite. Still works, but not quite as intuitive.
The tube also has a plastic disk glued on the top, with a slot cut out for the wire to travel back and forth in. Again, not necessary, but this way, the hole in the benchwork is almost completely closed off. Not sure if that is necessary, but I did it. There are some more photos in a thread of mine called "Woohoo finally laying track!".
I have some of the turn-outs at an angle to the edge of the benchwork. The electrical switch itself can be turned a little bit and the rod/knob will still work. And, the wire itself is also free to move a bit out of the exact direction of the electrical switch too. I’m guessing that with my set-up, I could operate a turn-out that was at a 30 degree angle to the edge of the benchwork.
On mine, I have 2” of foam and ¼” of plywood and ¼” roadbed, plus about ½” to the switch handle, so the wire is about 3 inches long. This gives me a lot of play and springiness to work with, things don’t have to be all that exact. If you layout is a lot thinner, then you will have to do some experimenting and testing. With a short length of wire, things could be very different, and require tighter tolerances of construction. The electrical switches have quite a large throw from front to back versus what is actually needed at the turn-out. The amount the wire moves can be adjusted by drilling the hole in the switch handle closer to the pivot point of the electrical switch.
If any of this is confusing, just keep asking questions. I’ll give you all the help I can, will take more pics, whatever you need, I’ll even see what I can design for a thinner benchwork if you need me too. How thick is your benchwork BTW? And, if you decide to go another route, that won’t hurt my feelings either.