View Full Version : Installing a servo to control a c55 turnout

6th Sep 2010, 04:29 PM
Based on some information in another thread about how difficult it is to mount a servo to control a turnout I thought I would make this short video.

Tools needed:
Pin vice and small bit
needle nose pliers
CA Accelerator

2 sided foam mounting tape
.015 music wire 2.5" long (YMMV)
scrap blister pack plastic (mine is from the servo package)
9g servo and control arm

The assumption is the turnout is mounted and hole drilled. You can do this how ever you like. I am using a LARGE hole because I don't want to have to get anything exact. Hole is about 1/2". Once everything is in place and the servo is working, I make a small piece of the same clear scrap plastic large enough to cover the hole with a slot in it for the actuator wire... after ground cover is applied you can't see the huge hole.

I am using the plastic below the sub roadbed to act as a fulcrum. This make it a lot easier to set up and allows MOST work except for the mounting of the plastic and servo from above the table. If I mounted the fulcrum to the servo, alignment would be more critical and need to be done from both bottom and top at the same time. With this method, as long as the servo is centered and you are ABOUT in the center of the throw of the control wire, all is well!

I mention sizes in the captions, but they are not exact at all. My goal was to make all parts on this as non critical as possible and alignment as easy as possible. The servo in the video is one that is right at the edge of the table and easy to film. Servos that are a longer reach are a little more difficult, but not that bad. I can do them with a long set of forceps back to the full 2.5' depth of my layout with out crawling under. This is possible because alignment with this setup is not hyper critical. Close enough almost always works!!

Please pardon the spelling in the video... it is my day off and I didn't want to bother re editing it after I uploaded it to YouTube.


6th Sep 2010, 05:20 PM

That looks easy! (After you probably spent hours figuring out the best way to do it!) How long do you think the piano wire could be and still work correctly? Would it work for instance passing through a 2" foam layout base?


6th Sep 2010, 05:25 PM
Some experimentation would be necessary. The fulcrum will be further away fro the throwbar, so you will lose some force but gain some throw. The wire would need t stay thin so it does not damage the turnout.... but I would bet it would work.

6th Sep 2010, 05:31 PM
Thanks a Lot Sean I recorded and saved a copy to my computer with the Relay Video Capture software that I posted a link for (No I am in No way affiliated with them) it's expensive $39.95 but it's times like these that I love having it for capturing what you just showed me, now no internet I can still watch your video for later reference, plus I saved your text to a word doc to go along with your Great Video:)


3rd Jun 2011, 11:20 PM
You can mount the servos on their side too. All you need to do is cut off unnecessary servo arms and enlarge one of the holes in the remaining arm and insert a small cotter pin. Use the hole in the end of the cotter pin to throw the music wire

4th Jun 2011, 02:49 PM
As the servos have their origin in the model airplane hobby, I imagine other airplane devices could also serve us. I'm thinking of pushrods and belcranks in locations where there is insufficient space to mount the servo directly under a turnout.

5th Jun 2011, 06:52 AM
Your method is easier then using the crank method, I see you don't use tubing for the wire. Next time I will drill the holes before installing the turnouts. Thanks for the tutorial.

5th Jun 2011, 07:53 AM

That looks easy! (After you probably spent hours figuring out the best way to do it!) How long do you think the piano wire could be and still work correctly? Would it work for instance passing through a 2" foam layout base?


Some experimentation would be necessary. The fulcrum will be further away fro the throwbar, so you will lose some force but gain some throw. The wire would need t stay thin so it does not damage the turnout.... but I would bet it would work. I'm not sure if someone here posted it, or I saw it on Tim Warris' YT channel, but he demonstrated nicely how to deal with the .15 wire in a foamboard application by soldering it to his regular HO wire, keeping the stiffness intact. This is a great alternative to a bell crank. Essentially you sister the 2 wires, wrapping them with copper strands, solder, and extend the .15 an extra 1/2" or so before the bending it at the deck. Worked great...I'll see if I can figure out where I saw the video.

6th Jun 2011, 04:10 PM
Just a quick note since I see this made the front page. Some users have reported issues with using the foam tape I am using. This has been traced to differences in the plywood base I used. If you have issues with the tape holding, there are various brands or strengths that can be used. I have also successfully used hot glue... just don't burn your fingers.

20th Jun 2011, 12:06 PM
That was phenomenal! So many switch control methods in the press are so laborious and sometimes expensive that it doesn't justify the effort. This is ridiculously simply, fast and effective!

21st Jul 2011, 08:36 AM
Hi, thanks for the video on installing servos. I have started to install a number on my layout but I am finding that the servos often buzz and make the singlet very hot to touch after I have set them up. Usually this does not happen straight away so I think the servo is all setup correctly but then later it will make a buzz, then it stops for a while and then after more use it starts to buzz again. This does not happen all the time but at random. Has anyone else come across this issue and if so interested as to how you fixed it as I am finding it very frustrating as I have checked that the wire is not hitting anything and the servo is no where near its end point and the throw is not putting too much force on the turn out end points either so i am stumped as to the random cause. This has happened on alot of my servos now and I have tried mounting them both using the mounting kit and on there side with the same result. Really appreciate any advice anyone can provide.

21st Jul 2011, 08:47 AM
I cannot say for sure, as I have had this problem. I use very thin wire and use it's natural spring ability to allow me to use full throw of the servo. My feeling is this puts less strain on the servo and turnout than using a stiffer wire and having to adjust the servo to use less throw. Perhaps you could try that? These 9G servos are not very tolerant of being over driven.

21st Jul 2011, 06:24 PM
OK thanks Sean. I am using the mount kits and wire which I purchased from Tam Vally so thought that was the correct wire to use but maybe it isnt. I have also been setting my servos up using the method desccribed in the mount kit which attaches the wire to the servo arm and then insert through the hole in the mount through the plywood and into the throw bar from underneath. Due the mounting it makes it difficult to ensure the points are centered. I think I will try the way you have shown on your video with the wire bent into a small L and then put through from the top and just left in the servo arm rather than attaching it and see if it makes a difference. Really appreciate your help. This is great forum and as I progress I will post some of my findings on different things as well to hopefully assist others.

21st Jul 2011, 09:57 PM
Please let me know how it goes. So far it is work well for me. I drill really big holes and then cover them with a thin piece of plastic with a slot in it once all is mounted and working.

Te key for me is using the entire throw of the servo. That requires really thin wire so you dont rip the points out of the turnout. I think the wire I was using was .015? or .022? I really cant remember. In long strips it is so flexible that you would think it would not work, but when cut in 3 or 4" pieces is it much firmer.

22nd Jul 2011, 02:23 AM
Thanks Sean. I tried the way you showed on the video but I couldnt get the points to throw properly. Not sure what I was doing wrong but I have found using a combination of your way with the L wire through the top and using the mounts which i purchased from Tam Valley I have now installed 1 servo without buzzing (had to program the singlet manullly though as the auto program still made it buzz). I think dropping the wire from the top loosely into the servo arm, rather than the way I had done it per the mounting instructions, which is attach the wire to the servo arm and feed through from underneath, is better as your way I can ensure the points remain centered. I think when putting the wire up from underneath even though I have some platstic keeping the points centered when I remove that plastic before setting the singlet end points if I was even slightly out in my servo placement it was moving from center. I suspect that was why I was getting the buzzing mainly in only one direction. Thanks again much appreciated. Just 51 more to go now!! ;)

23rd Jul 2011, 04:37 PM
Here is a VERY good tip by Sherman to prevent binding and issues with the wire turning in the throwbar. Wish I had though of it!

16th Dec 2011, 12:59 AM
What controls the servo?
What type of servo did you use?
What did it cost?
Where do you get piano wire... a music store?
So many questions.

16th Dec 2011, 02:05 PM
What controls the servo? http://www.nscale.net/forums/showthread.php?17760-Tam-Valley-Depot-servo-controllers&highlight=Tam+Valley
What type of servo did you use? cheap 9G servos http://www.ebay.com/sch/i.html?_from=R40&_trksid=p5197.m570.l1313&_nkw=9g+servo&_sacat=See-All-Categories
What did it cost? http://www.nscale.net/forums/showthread.php?17760-Tam-Valley-Depot-servo-controllers&highlight=Tam+Valley
Where do you get piano wire... a music store? Any hobby store should have it.

27th May 2012, 10:46 AM
Ca will hold that piece of plastic to plywood? How about if the ply is painted?
Why not just secure the servo directly to the ply with CA?

27th May 2012, 12:19 PM
I suppose CA would work for the servo. Just seemed more flexible to use the tape. I have also used hot melt glue in a few places as others have. Not sure how CA would work over paint since mine is unpainted birch ply.