Friday, September 14, 2012

I am using two types of switch machines on the railroad. All of the switches that will be driven by the CTC system are driven by tortoise switch machines. These switch machines are reliable, easy to install (we are using hot glue) buy a tad pricey.

For local sidings I am using Bullfrog manual switch machines from Fast Tracks. These work very well when you can line up the control rod with the direction of throw rod on the switch machine. Unfortunately, I cannot do that on the lower level of my layout out. To protect the controls, they are mounted along the bottom edge of the layout and recessed by about an inch from the front of the fascia. The picture of the ruler did not come out so well, but they are about 7" below the surface of the layout.

I also have a rule that when the control rod is pushed in, the switches are aligned for the main. Further, for crossovers, I use two control rods about a couple of inches apart that move in or out together. This means one of the two control rods has to be curved 180 degrees to thow the turnout correctly. Given all of this, I wound up bending the control rods a lot. Since they are purely mechanical, the bends create a lot of friction making the control rods hard to move, and worse results in the control rods being pulled from their mountings.

What I needed was a way to transfer the energy applied to the control rod 5 or more vertical inches while possibly changing its direction. To do this I created the following linkages.


These are pretty simple. A piece of PVC tube with some armatures glued to each end, mounted on a dowel that is glued vertically from the bottom of the layout. The armatures can be glued at any angle to each other to minimize the curving of the control rods (red tubes above). I then use a solid wire to connect the other armature to the manual switch machine. This does the job perfectly. It transfers the energy to the base of the layout, and allows pushing a control rod to either pull or push the turnouts throw bar. I could probably do crossovers by having a double armature at the top of the PVC rod that would push one side while pulling the other.

Making the armatures is simple, but tedious. The armatures are made out of very thin plywood. I am currently using 3 ply 1/16" plywood. This may be a little weak and I may switch to a 4 ply plywood. I cut these from the sheet in the following pattern.
A pair of armatures is cut from a 3/4" by 3 inch strip of plywood. The center point for the large wholes (7/16" diameter) is made by marking the corners of a 3/4" square at each end and connecting the corners with a line resulting in a X. X marks where to drill the whole. The little hole (3/32" diameter) is positioned at the center line of the strips. Cutting them apart results in the armatures at the top of the picture.

The armatures are then glued to a piece of 1/2" inner diameter PVC tubing cut to the desired length. Make sure that everything is lined up correctly so that it will turn easily when the 7/16" dowel is inserted into the tubing.

The dowel is cut 2 inches longer than the PVC tube. This is mounted vertically on the bottom of the layout. I use a square block of wood cut from a 1x2 with a hole drilled into it to glue the dowel into. Once this is made, I slip the PVC tube with the armatures over it and glue a small piece of wood on the end of the dowel to keep the tube from falling off.

This is then glued to the bottom of the layout (using hot glue), the rods are connected up and it is ready to go.
The result is that the push rods are easy to move regardless of the angle of the throw rod to the angle of motion of the control rod.