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Skull in a Cage WIP

1468 Views 4 Replies 3 Participants Last post by  Neverhart
A friend requested a Halloween prop for this year, and before I get too busy with my OWN stuff, I figured I'd get this together. Apologies for my wordiness, but I like seeing detailed builds here and have gotten lots of ideas for my own projects even when they're implemented differently, so maybe you will too.

The concept is a skull displayed in an attractive antique cage (as if the skull is likely to bite you if not protected... which it might.) The eyes will glow a soft red, and RGB LED lighting strips will provide ambient, changing light. The skull (I think I'm going to call him Yorick) can rotate and the jaw will move to audio I'll record.

I have a Bucky skull lying around that I did a Scary Terry servo job on, and I quickly hacked together a 1/2" PVC spine to act as a spindle, with a T joint attaching to the base of the skull and a 45 degree bend to make Yorick look up (I'm anticipating this being placed on a table or desk.) Then I built the box frame the cage will sit on with 1X2 furring strips. The base of the cage is 3/4" particle board I cut into discs.

Wood Table Plywood Furniture Hardwood

After some experimenting, I found a piece of leftover PVC that the 1/2" PVC fits down into perfectly, and has a Teflon-like coating that allows for rotation of the smaller pipe within.

Wood Table Machine Electronics Plywood

The 1/2" sticks out of the bottom of the table top, so I can rotate the skull from the box. The benefit of doing it like this is that it will allow me to run the necessary wiring up to Yorick's brain case (empty... he's not a very smart fellow) where the jaw servo and LED eye electronics are hidden.

Wood Room Table Furniture Plywood

Then came time to figure out how to rotate the spindle... I thought about a servo arm with a pushrod, but I've been working on a CNC platform and my head must have been stuck in that world, because I started thinking about using pulleys and a timing belt. I'm no engineer, and know next to nothing about gears and timing, but I did some research and found that the timing belt I had was GT2 standard. I found a GT2 gear/pulley/not sure of the right term on Thingiverse, designed by someone who knows a lot more than me, and made some modifications to the linkage in Sketchup to allow it to fit around the 1/2" PVC. I printed it up on my 3D printer and attached it to the spindle. It was a hack job, but worked as a proof of concept and did indeed rotate the spindle, although slowly.

I had some cheap eBay stepper motors with drivers lying around, and an aluminum GT2 pulley from my CNC project that attached over the shaft, so there's my drive pulley. The belt is a small section of the GT2 belt from my CNC project SCOTCH TAPED together. I might order a specifically-sized belt if I can't think of a way to ruggedly close the belt.

Wood Hardwood Table Plywood Floor

Floor Room Plywood Wood House

To attach the cage together, I'm running 6X 1/4"-20 threaded rod through the baseplate and a ring, through (yet more... guess what I have a lot of lying around?-) 1/2" PVC (the bars of the cage), through the top, capped off with cap nuts for a nice old-timey/Steampunk vibe. The top of the cage is a dollar store plastic bowl. All will be painted and trimmed and antiqued with whatever I can find lying around.

Furniture Table Machine

So still lots to do, but it's coming together! I'm working on a smaller spindle pulley to make the rotation a little faster. I use Arduinos for controlling the whole mess, and an MDFLY board for playing audio... the jaw will be animated by the audio with the awesome Scary Terry/Halstaff/Everyone involved Audio to Servo circuit. I built like three of them a couple years ago, as they're the easiest way I've found (short of actually BUYING one - egads) to implement talking animation. Have to mention I was inspired by Mad City's Hydrotherapy Finished Prop Video on YT, a really creative and well done build with lots of vibe.

Thoughts and ideas from brighter/more experienced brains welcome... I'm what you'd call an advancing novice to all this, with a pretty good mechanical instinct all backed up with a blissfully ignorant and arrogant denial of how it SHOULD be done. (-:
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Wow that looks amazing, I can't wait to see it finished! Whatever your skillset it ;), you have applied it well here! :)
Thanks T!

Gotten a little bogged down with details, but I'll have more pics and updates soon.
This is really looking very cool. I look forward to seeing this finished!
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Thanks Halloween Lady!

Been working slowly but surely on this prop, mostly on the finish... which you can't see in this vid; I'll post daylight pics soon. Functionally I got the RGB LED lighting on the roof of the cage working, along with Halstaff's excellent audio-servo driver driving the skull's jaw along with the audio, and the eyes in the skull glowing a ghostly white... if a little cross-eyed! (Hey, reanimate a severed head and see how straight YOUR eyes are!-) I cut the cool frosted plastic eyeball blanks from Monsterguts.com in half to get the diffusion on the eyes. Pingpong balls are just a little too big to fit in the Bucky's sockets.

The whole thing is being driven by an Arduino... the Uno has some good power regulation so I can plug in a 9V DC adaptor and use that raw voltage to drive the MDFly audio board and LED strip tape, and use 5V to drive the rest without needing multiple power supplies or external voltage regulators. I think the flickering visible in the video is due to the relatively weak 650mA supplied by the wall wart I was using.

The weird slating on the test audio is because I want the prop to have 3 modes: Museum Mode where the skull simply swivels back and forth with some creepy music, Scare Mode with some jump scares, and Story Mode where the skull will tell stories of his origin and background. I've been writing a background story for him to help figure out who he is and what he'd say... which is kinda fun. Most of my props have just been scary for scary's sake.

Suggestions welcome!

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