X8 360° Pan build log

by RCExplorer | May 13, 2013 | (32) Posted in Projects

This is the build log for the 360° pan used on the Skywalker X8

(Click here for the Review video)

The goal with this setup was to get a really smooth, self centering 360° pan with great resolution. A pan that felt "natural" when moving, centered perfectly and had such high resolution that you can position it perfectly with the stick.

To achieve this I decided to use a 10 turn external potentiometer, modify a servo and gear it down.

This is the servo I used, a GoTeck GS-D9257 Coreless, digital, ball bearing tail servo.

The top taken off.

Most servos have some kind of mechanical stop that keep the potentiometer from being overturned and destroyed. Some servos have "better" stops than others. This particular servo has the "bad" kind of mechanical stop, in the form of "filled" in teeth on the gear.

I used a dremel with a cutting disk and simply made some teeth. It worked out great.

Some servos use the internal potentiometer as the stabilizing shaft for the output gear, which is not great as normal potentiometers have a build in mechanical stop. This particular servo didn't use the pot as a riding shaft. Instead the gear rests on ball bearings and all I had to do was to remove a little insert that connects the output gear to the pot and the problem was solved.

Normally the built in 1 turn potentiometer is used to sense where the servo horn is located. To get better resolution I decided to use an external 10 turn potentiometer. To connect this external pot I first had to desolder the old potentiometer.

For ease of installation I simply added a servo connector to the three pot solder pads. This way I can easily connect and disconnect the external pot without having to desolder anything.

The servo done. The 10 turn 5K linear potentiometer sitting in the foreground. (If you plan on doing this your self, make sure the potentiometer is a LINEAR not logarithmic)

Soldered the servo connector to the pot. The center leg is the important one to get correct. If the servo turns the wrong way you can simply swap the two outer leads by turning the connector around.

Hooked up some gear I had laying around for testing. When swapping the potentiometer in a servo always check the number of turns used on the pot by the servo. A servo never uses the whole range of the pot so this step is needed to figure out how many turns the servo defines as it's full range. In my case the servo only used 5 turns, which is half the range of the pot.

With that knowledge I went to the local hobby shop and picked up some gears. A Blade450 helicopter main gear which has 140 teeth and two RC car gears with 25 and 29 teeth.

I mounted the 25 tooth gear on the servo. This results in a gear ratio of 1:5.6 (The servo has to make 5.6 revolutions before the the camera turns 360°) The servo speed is 0.07 seconds per 60° of travel, which means that it's going to take around 2.5 seconds for it to make the camera go from looking straight back one direction to looking straight back the other direction. A nice, smooth speed.

I mounted the 29 tooth gear on the pot using a couple of brass tubes. The gear ratio on the pot is 1:4.8 which ensured that I got the full 360° range.

Time to make a simple mount.

A servo horn happened to have the correct hole spacing to use as the center piece for the main gear.

I used a 4mm screw and two ball bearings to mount the main gear to the tray.

Bottom view. The ball bearings ensure smooth, slop free movement.

A piece of balsa, zip ties and a Velcro strap mounted on the main gear to hold the gopro.

Tada! All ready to go.

Mounted on the X8

I'm extremely happy with the results. It's so smooth, precise and easy to use. Trouble is that it feels so natural to look around that I now miss having this feature on all my FPV planes.

Hope this guide was of use to you! Keep up the great suggestions.

COMMENTS

RCmaniac on May 23, 2013
Cool! It looks kind of complicated to build! :) I might try it!
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x3mperformance on May 23, 2013
This is only looking complicated. It's an easy build, when you get at it.
Just belive in your selv, and give it a go.
Remember, a Dremel and a fancy Weller solder station are not Essentials, you can also do it with much more basic stuff, like a 20 watt solder iron, a small hacksaw, etc.
Just don't skip on the parts, they are nessesary, to perform well. Cheeper stuff is arround, but!!!

Yet another awsome article David. Keep 'em commin'
Rene'
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Jake Wells on May 23, 2013
You're a superhero.
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liveyourdreamsRC on May 23, 2013
Wow, a little reseaching to find out what some of the vocab is but looks easy enough. Your build logs are amazing and easy to follow- Keep it up Dave!
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liveyourdreamsRC on May 23, 2013
Maybe now you can make it have tilt too!
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liveyourdreamsRC on May 23, 2013
OMG! Just saw flitetest with Dave's spectacular build JA 37 Viggen in the AMA newsletter! Cool to see you guys there. Are you creating a partnership with them?
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Good Kebo on May 24, 2013
Thanks for posting this
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Splatwillicrash on May 25, 2013
David, if you are any good at Google Sketchup or any 3D cad/cam package that will output SKP files, I have access to a couple printerbots, a Plus and a Jr. Send me the files and I will print you a few of the gears and maybe even some sort of mount. As long as you build me one of course.
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tramsgar on May 25, 2013
GJ David! Did you at any point consider using actuators?
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Battershell on May 25, 2013
Awesome David! Super smooth setup and video from this project!!!
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hasamalvides on May 25, 2013
Please guys, add this on the Store. and all the other projects you make.

great article
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derabbink on May 27, 2013
Awesome build log! There is just one thing blocking me from building it myself: that brass tube you used to fix the gear to the pot... how do you find something like that? That is, how can you find parts to fix the gears with?
I agree with hasamalvides: put it in the store
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mattplaneflyer on May 29, 2013
Great job David!
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xtrmtrk on September 29, 2013
Would love to see this as a kit in the store.
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Mastrmindz on August 23, 2014
I cannot watch the video. Can you make it not private plz? I really would like to see it. Gracias.
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andya-uk on October 19, 2014
I've done a modified version of this design.

The servo i used was the metal-geared version. It has the advantage of a metal stop pin that can be pulled out with pliers, sparing the need to cut gears.

Also i turned the servo around to save space, plus fitted smaller gears of close enough ratios to still get 360 degrees. These are Traxxas #4472, #3945 and #3947.

Here is a video of it in action. The tilt is from Hobbyking, and this one is designed to be hung upside-down under the plane.
https://www.youtube.com/watch?v=WollUUELnvg


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X8 360° Pan build log