# 3-Axis Skull in progress 1



## Neverhart (May 28, 2012)

Been a long-time admirer and student of Halloween Bob's now-classic 3-axis build. It took probably a year to read through all the material and get ready to start. Every tutorial had their own opinion on how best to do it, so after going through it all again and again, I eventually got my hands dirty.

Last year I modified a Bucky with a jaw servo a la Scary Terry's instructions - if you're just starting out with servos I'd recommend trying this hack first... gives a good feel for the skills you need going forward. I ordered one of his audio to servo driver boards, but it mysteriously stopped working the week before Halloween - it was probably me... I had no idea what I was doing lo those long months ago. (-:

Anyway, the Buckys look great but are very heavy, so for the 3-axis build I decided to use a Lindberg. The only weird thing about the Lindberg is that the teeth don't want to sit in place very well. I was trying to use Loctite, but you probably want something more gooshy to fill in the gaps. Most of the teeth wound up falling out as I wrestled with the mechanics.

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Couldn't find very thick plexiglass, so I used L-brackets to hold the servo plate.

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It's hard to believe, but most of the techniques out there will work to some degree or another. Don't worry too much about it until you get it together and can see where you're going to have to make modifications. This is the underside of my servo plate... it seems to work decently, but I'll probably have another go at smoothing everything out.

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Buy plenty of 2-56 ball links and swivel ball link with the included hardware. Experimentation is the best way to figure out how it's all going to work together. Also, get the rod/plate combo working before you worry about how the skull's going to fit in the picture.

Also, I like using the Arduino to do initial testing with any servo movements - it's quick and easy. I have a sketch that centers (90) the servos, which I use before attached the servo horns. I have another that goes back and forth between a min and max value to test where the range of motion should be. If you're taking things to Picaxe, be aware that the servo values will NOT be the same.

So once the 3-axes were in place, I just kinda eyeballed where the jaw servo needed to go. You probably want to drill the hole for the jaw linkage BEFORE you finalize the jaw servo placement just to make sure it works... the placement of the ball linkage on the inside of the jaw will heavily influence where you need the servo to be. You really can't see the hole where it's located, so don't be afraid to rout it out to give the rod enough play.

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This last pic shows the jaw linkage from servo to ball joint (which isn't as dirty as it sounds.)

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Once I got the linkage together, I quickly tested with the Arduino, then moved it to the Picaxe to find the servo values. I'm going to use Halstaff's Audio Servo Driver circuit to animate the jaw. I'm not sure if I want to use VSA to program a routine, or create a more random movement for the head with a Picaxe, and just feed in audio whenever I want. I don't have a cohesive show idea together yet, so maybe that will dictate what I wind up doing.

Here's the jaw test, where it's picking random servo positions between the min and max with a very small delay to make sure the mechanism can handle it!






Thanks for watching!


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