Some Simple Switch Machine Solutions

Mounting Tortoise Switch Machines

The problem with attaching the Tortoise machines is that the built-in mounting ears are too close to the machine to reach easily with a screwdriver. Plus the machine is small and it's hard to position it critically and drive the screws without pushing the machine out of place. Some vendors sell mounting plates for the Tortoise, however there is an easier and less expensive solution. To alleviate these problems attach each Tortoise machine to a scrap of plywood. The size of the plywood is not important so long as it extends well past the machine proper. The plywood is, in turn, mounted to the underside of the layout. The plywood forms a 'handle' that makes it easy to position and screw the machine in place without movement.

These photos should be self-explanatory.











You'll notice in the pictures above that the actuation mechanism of the Tortoise machine simply extends past one edge of the plywood mounting plate. In this way it is not necessary to drill a hole for the actuation wire through the mounting plate. Also note that I have pre-drilled and countersunk holes for the mounting screws. Four holes are not really necessary, but it provides some flexibility in where the mounting screws will be driven. Depending on your track construction the combined thickness of the mounting plate, subroadbed (plywood) and roadbed can exceed 1". This would be too thick if you use the music wire actuator that comes with the Tortoise. If this is the case cut another wire actuator and make it longer; the Tortoise instructions include a template for the actuator.

Mounting Servos as Switch Machines

Mounting radio-control servos for use as switch machines presents a problem. Some manufacturers sell mounting plate for servos but, as far as I have been able to determine, only for the miniature/micro servos. If you want to use the full-size servos or you need a lot of these mounting plates they are not a solution. There is a simpler and less expensive solution, glue the servo to a right angle bracket sold in home centers for building decks.





The bracket is Simpson 'Strong Tie' A21Z, note: this is the right angle bracket with one arm longer than the other, that's the arm that the servo is glued to. I used Gorilla Glue to attach the servo. I roughed-up the bracket and servo with sandpaper before I dampened the bracket with water and applied a THIN coat of the glue to the servo, then clamped the two together. Use a thin coat, otherwise the glue will foam up all over the work.

Here's the servo switch machine installed:



The machine can be installed above the table as well which is handy in areas of hidden trackage as the machine is easy to access for adjustment or replacement.



The servo switch machine is mounted on a scrap of 1x2 lumber (actual 3/4" x 1 1/2") to provide some height and thereby additional throw for the actuator wire. Notice that the PC Tie throw bar has been extended with another length of PC tie soldered on so that the switch machine can be mounted far enough to the side to clear rolling stock. The extended throw bar is supported by a wooden tie to prevent the throw bar from sagging.

For fitting the actuator arm, made of music wire, to the servo crank I came up with what I think is a novel solution which you can see here:



I bent a length of wire into the shape above. The length of the straight section to the right should be enough to reach up through the subroadbed, roadbed and through the throw bar on your turnout. If in doubt, make it longer, any excess can be cut off after installation. The form of the wire on the other end is shown in the detail close up here:



The distance between the bends should match the hole spacing on two opposite arms of the servo crank so that it fits like this:





In case it's not obvious how to get the bent wire into the servo crank, here's a short video on how it's done:



The self-retention feature that you see in the video works because I am using relatively stiff 0.039 wire as a actuation arm. That allows the right angle bend at the end to exert enough outward pressure to hold the arm in place. If you use significantly thinner wire this might not be the case.