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…...............--- Turnout Servo Mount for Two Limit Switches ---

….............--- Print files for the mount ( HERE ) ---

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I have a servo mount for turnout control that you can mount one limit switch to on thingiverse.com ( HERE ). The limit switch could be used to change the frog polarity, signaling or LED's or possibly something else. What if you need to control two different things, such as, maybe the frog and signaling where you can't control both off a single limit switch.

You can find servo brackets with the option for two limit switches so I decide to follow suit and add a second limit switch mount to my servo mount. One item of note is that you can adjust both of the limit switches to determine when the servo arm hits and activates them. Some of the servo mounts I've seen the limit switches are in a fixed place.

Using a servo for turnout control one needs to first set the servo throw to that it throws the points but doesn't over power them with too much pressure. The throw will be different depending on the turnouts scale and how far it is located above the servo. With this mount and my servo mount for a single limit switch you can set the throw for the wire going to the throwbar and then adjust the limit switch so that it make contact with the servo arm and is activated.

There are two mounting holes on the limit switch. The switch in our application will pivot on the top hole and the screw there. Once it is in the proper position you can run the bottom screw into the curved recess there. That screw will then keep the limit switch from rotating out of position. This works the same on the mount for one or two limit switches.

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The mount and the servo are quite small.

After the bracket is printed I drill the hole for the throwbar wire to 1/16” (.063”). I drill the other mounting holes in the bracket for the servo, the limit switch and the bracket mounting holes to 3/32” (.094”). I drill the pivot hole in the limit switch to 7/64” (.109”) and the hole for the set screw to 3/32” (.094”).

I use #4 screws for all the mounting. 1/4” to mount the servo to the bracket. 1/2” for the pivot screw on the limit switch. 3/8” for the set screw on the limit switch (some times 1/2”). 3/8” to mount the bracket to the underside of the layout.

NOTE: If you are metric use the appropriate screws and pilot drill bits to work with the screws you are using. If you don't drill the holes out on the bracket you are risking breaking it when the screws are put in, especially the narrow arm on the single limit switch bracket that holds the servo on one side.

It can be difficult at times to mount a servo in the correct place under the turnout and it needs to be pretty accurately located.

I've tried to make that a lot easier with some tools shown above that you can also print out. These will make it very easy if you are doing this as you lay track and before the turnout is in place.

Locate where you need the wire from the servo to come through the layout's surface. Will it be in the middle of the throw bar between the rails or outside the turnout and under the extended throwbar on one side of the turnout or the other? With the location of the throwbar wire hole determined drill a .025” hole there. Reach under an install the tool shown above or in the next image. If you can't reach this from the side of the layout you will need a helper or tape it to the bottom of the layout after pushing it up through the hole.

Next rotate it from the top of the layout using the pointer on the top to help locate it with the pointer pointing down the track in one direction or the other depending on which direction you want the servo mount pointed in. Next....

….. take the 'Drill Jig Grabber' shown above and slide it down the pointer rod and use a set screw to hold the 'drill jig' from falling to the ground.

Now you can go under the layout and using the drill jig drill two pilot holes for the servo mount. The should be positioned exactly where you need them. You will only be under the layout for a couple seconds drilling the two holes.

Next take the the servo mount with the servo attached, limit switches attached and a throwbar wire attached to the servo arm. Also have the two mounting screws in the mount and sticking out just a bit. Under the layout put all of that into place with the throwbar wire going up through the 1/4” hole. You should be able to move it around slightly until you feel the mounting screws drop into the pilot holes. Run the screws in and you are done.

This should take less than a minute under the layout and the wire to the throwbar should be close to perfectly centered in the 1/4” hole as shown above.

If for some reason you need to you can put the mount and servo up under the layout and grab the throwbar wire from above and put the 'Throwbar Grabber' (shown above) on it and it will hold the mount and servo from falling to the floor. This shouldn't be necessary thought if you started the screws in the mount and have them sticking out a ways.

When finished you should find the throwbar wire centered in the 1/4” hole. Slide the turnout down over it with the wire going through the throwbar hole and finish installing the turnout. When done if you are using one of the controllers shown and described ( HERE ) you can …..

adjust the servos throw as shown above or ( HERE ). It is a good idea thought to get it close as shown above with the test rig before installing it. Do that and use the mounting tools above and mounting the servo will be easy and fast with minimal time under the layout. Also you can have all of this for under $10 a turnout as described ( HERE ).

You can find the files to print this on my thingiverse.com account ( HERE ).

You can find all the files to 3D print this object and others on my thingiverse.com account ( HERE ).

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