Thread: Converting Gemmy Skull to 6 Axis Animatronic

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Hi, I'm Rob. I thought I would document the conversion of a Gemmy Animated Scary Skull to a 6-axis animatronic (nod, pan, tilt, eyes X, eyes Y, and jaw), since I have not seen this done yet. I just got my 2-axis eyes working last night after a lot of trial and error, and have the jaw servo installed as well. All seems to be working well other than some occasional popping with the eyes due to the mounting method I'm using (may be revised if time allows). I'm running VSA to control it all via PC, interfaced thru a Parallax USB servo controller.

I have gutted all the original workings of the skull, other than the eye linkage and the jaw lever. I have used Magic Sculpt epoxy clay to re-sculpt the eyes/brow area (blends into the plastic amazingly well), add a zygomatic arch to his cheeks, and form some sockets on the inside of his face for the eyes to fit into. The sockets are lined with Teflon tape to make the action smoother.

Next step is to make a bracket to hold the skull servos and rod end, basically Halloween Bob style but adapted to a skull that opens vertically instead of horizontally.

Why did I choose this skull? Well, for $12 it's pretty nice out of the box, but if you get tired of the stock cackling, it's basically ready for all kinds of modding. In an evening, you could swap out all the motors for servos, and have a nice little prop with controllable 1-axis eyes and jaw movement. It's also got a nice paint job and lots of character--though he's a little more goofy than scary.

I'll post more details as I go along, but for now, it's nice to be here with so many folks who are so crazy about Halloween!

UPDATE: Here's a video of his facial animation thus far.

[ame="http://www.youtube.com/watch?v=vvXq8tmFZ2c"]YouTube - Skull Animatronic 1[/ame]

I for one can't wait to see the innards of your creation. I have been looking for an answer to the two axis eye movement. One that won't take six weeks and drain the pocketbook. Please, post more. By the way, he looks great.

I too am interested in this project.
I have a few of these. My issue is the 2007 models have the eye linkage.
The 2008 models don’t have the eye linkage.

I have the the 2008 models.

Thanks for the comments. I've updated the first post with a Youtube video of my work in progress. I'll try to post a video of the inner workings tonight. I've still got a long way to go before I have the head motion working and that really needs to be done by the end of Saturday. I've still got to paint this sucker and get a foam coffin slapped together--just one weekend left guys!

AEGnome, how are the eyes set up in the new model? There is no bar linking the two eyes together? How odd.

The 2008 model eyes only light up, they don't move.

Here is a picture of the back of the eyes.

Wow, they got a little cheap this year. Looks like everything's there except the linkage bar and the cam mechanism though--exactly the same as the old version other than that. I wonder if the eyes even have the pegs on top and bottom for swiveling. So if the posts sticking out the back of the eyes still have the holes in them, should be pretty easy to make your own linkage, just cut out a piece of strong-tie and drill some holes, grab some bolts and a couple washers, not a lot of work and might actually be better than the plastic linkage which is a bit wobbly anyway, and bulky as well. I ended up cutting a lot of it away to allow the up and down tilt.

looking great! Love the alternative skull idea. I too am hacking an alternative skull for 6 axis. I'd love to compare notes with you when I post it up!

Hehe, I've always got to try something different. Only problem is since it's not a Bucky or a Lindbergh, I'm pretty much on my own. Anyway, I had 4 of these things, so I had to do something with them! The other three I'll probably prop up next to random tombstones in annoying default laughter mode. Maybe next year I'll have them singing or hitch hiking.

So here is a video showing the guts. It's basically the same idea as the x and y axis for the Lindbergh skulls. One servo pulls up/down, one pulls left/right.

[ame="http://www.youtube.com/watch?v=9vqYdD_3Xo8"]YouTube - Inside My Skull[/ame]

Oh, for my fellow servo noobs, here's a trick I learned the hard way this morning--when you are attaching the linkages, leave the screws off the servo arms until you have tested the motion at least once. Leave the servo arms on while test fitting and checking the range of motion (manually turning the servos without power connected). Once everything looks good, TAKE OFF ALL THE SERVO ARMS before plugging them in to the control board or connecting power. Once power has been connected, the servos will center themselves. Now turn off power, and disconnect the servos.

Now, you can reattach the servo arms, making sure that you turn them to a neutral position (i.e. the jaw is halfway between closed and fully open, the eyes are pointing straight ahead, etc.) before popping them on the servos, without turning the servo axles themselves. Once again, check the range of motion by turning the servo arms, to ensure you still get the desired movement without hitting any internal obstructions. You may want to leave the screws off until you have at least tested part of your routine. Once everything seems fine, tighten up the screws until they are just snugly in place.

This process will ensure that when you power up the skull again, the servos should have plenty of space to do their initial centering without meeting any resistance. Also, when you disconnect your skull, you may want to reset the servos to their default state first (leaving the defaults at their initial settings during setup) if your software has a reset feature feature (VSA does), so everything is relaxed and centered the next time you power it up.

I made the mistake of setting my jaw's neutral position to fully closed when I installed it last night. Unfortunately, I was just a little off on where I thought "centered" was, and when I fired it up this morning to show my buddies at work, there was a horrible crunching sound, and I could hear the servo straining. I pulled the USB plug and the jaw went slack. Not good. The gears were not engaging and the jaw linkage had been forced way past the closed position, which told me somethin' done busted. When I opened up the servo, sure enough, one of the gears had about half the teeth stripped off. Fortunately, it was only a 160 degree servo, of which I am using less than 90 degrees, so I just turned the gear around and engaged the other half of the teeth. Luckily, it worked and I was spared having to order a new servo this late in the game.

I'll post some photos tomorrow showing more of the construction.

It's tomorrow...uhm, here's a few pics.

First, I added sockets for the eyes using Magic Sculpt epoxy resin. I can't say enough good things about this stuff. It's great for adding support structures inside, and for sculpting details outside, cures virtually rock hard, cleans up with water (before curing). I formed the sockets by placing two donut-shaped pieces behind the eyes, then wrapping the eyeballs in plastic wrap, and pressing them into the donuts until they lined up at the depth I wanted them. Then I wiggled the eyes free and smoothed the clay out with water.

They didn't come out perfect though, so I ended up removing some lumps with a dremel and a utility knife. Last, I lined the sockets with adhesive Teflon tape from Mcmaster.com to smooth out the action of the eyes and protect them from abrasion.

Oh, you can also see the spring which is screwed into an existing screw post between the eyes. This will end up holding the eyes in place.

Next I bridged the gap in the eye linkage with more epoxy. I also inserted a thin washer between the eye post and the linkage to take up some of the wobble.

I connected a light gauge expansion spring spring using a piece of 2-56 threaded rod and a washer and nut on both sides of the linkage. This spring will hold the eyes in their sockets. You can see the post that the other end of the spring connects to in the first image above.

I made a bracket for the eye Y-axis (left/right) servo from a piece of Strong Tie, using a dremel with a cut-off wheel. The bracket is supported by the epoxy clay, but the large screw is drilled into the side of a screw post that is a structural part of the skull. The clay is stong, but does not support small screws very well. The holes in the bracket arms are tapped with 2-56 holes.

I cut down the existing jaw lever to avoid hitting against the servo, and drilled a hole for a 2-56 screw.