3-Axis Skull Mod for 12ft Skeleton

The 12ft skeleton (Skelly) from Home Depot is an impressive decoration, but needs an extra kick to make it truly incredible!!!

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I've been in the world of Halloween based animatronics for over 10 years and have even made a name for myself with my MonkeyBasic software, now available through

So it only made sense that once I got my hands on one of these that I would cut it open!

This is my first time creating the 3-axis movements (plus jaw) from scratch, typically someone else beats me to it so I decided to combine my 3D printing ability, my limited mechanical knowhow and give this a whirl. I'm quite happy with the results!

I'm pretty sure this will void the warranty on your Skelly! LOL

Many of you have asked, so for those that feel brave enough to cut open their Skully, I've decided to start offering the 3D Printed Parts for sale. They will be listed on my Etsy page here:

This project covers the construction of the mechanical parts and installation into the skull. It does NOT cover the electronics or programming of the routines.

I do not recommend doing this project if you are not comfortable with servos or animatronics. I'd recommend starting with a smaller 'normal size' skull first. Like those available from or

WARNING: You will be cutting large holes in your plastic skull as well as separating the jaw from the skull. You will also need to cut the metal pipe that protrudes out of the neck a small amount so it doesn't interfere. Be careful and make sure you are comfortable with this!!!

NOTE: This is not meant to be water-resistant!!! If you plan to keep you Skully out for the month of October, this may not be meant for you... or try to find a 2nd head you can swap in!


  • 1 × 3D Printed Parts (see external link to Thingiverse) For printing the parts of course!
  • 3 × Hitec HS-805BB w/ included Servo Arm and Hardware Hitec Giant Servos for Yaw, Roll & Pitch
  • 1 × Hitec HS-425BB w/ Servo Arm For the Jaw movement
  • 1 × Thrust Needle Roller Bearings with Washers 20mm Bore, 35mm OD
  • 1 × Flat Steel Bar (cut into 2 pieces) 1/8" thick, 1/2" wide

View all 13 components

View all 4 project logs

  • 1
    Interface assemble

    Start with the (white) 3D printed part called "Skull_Mech_V3_Interface" This connects to the neck of the skeleton.

    1. Make sure the shaft is smooth, sand it down a little if needed.
    2. Slide the thrust needle bearing assembly down (washer, bearing, washer)
    3. Screw in the two M3 screws (thread length around 12mm) at the top of the part. These will tighten the rotation servo onto this part later. Don't tighten the screws.
  • 2
    Rotation Servo installation

    You will be using the 1st level (blue) 3D part labeled "Skull_Mech_V3_1stLvl"

    1. Remove the servo arm (and screw) from the servo. 
    2. Position the Rotation servo as shown and attach with the included hardware.
      1. There are holes in the 3D model for aligning the servo screws.
  • 3
    Tilt Servo Installation

    Still using the 1st level (blue) 3D printed part.

    1. Install the servo arm shown (you may need to remove and adjust its position later on).
    2. Position the Tilt servo as shown and attach with the included hardware.

View all 21 instructions

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Montanadude wrote 3 days ago point

Am I confused or are the eyes in your video using graphics or oled's?  If so, do you have details for the setup and such for them?   Also, where exactly did you get the head as on thingiverse I only see the rest of the parts to print?  Thanks a bunch.

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martinisaacanywhere wrote 01/20/2023 at 20:19 point

I’d like to try this, but can’t find the links or files… am I missing something? 

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Nelson Bairos wrote 01/31/2023 at 00:46 point

Hi, the link to the files is in the links section. Here it is again:

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martinisaacanywhere wrote 01/31/2023 at 03:27 point

thanks! I can’t wait to try this. How did your progress come along for the coding?  Thanks ve had some success using chatterpi in the past, and now that some raspberry pis are back in stock, so I think I’m going to give that a shot for this project. Thanks again. 

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Nelson Bairos wrote 01/31/2023 at 13:59 point

@martinisaacanywhere Just an FYI that I'm working on improving the engagement between the rotation servo and plastic. As another comment below mentioned, it can be a week point. So I'd hold off printing the rotation part (white piece). As far as programming, I use a stick PC with Brookshire Software's VSA and my LifeApe software. I've been tinkering with PI but nothing ready yet.

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redpawFX wrote 11/02/2022 at 20:32 point

I printed this up for this halloween and it worked really well.  Thanks so much for the design!   I did upgrade the servos to  heavier duty  metal gear ones and  used a 1/4 scale servo for the jaw as well.  The only part I think could possibly  use a little tweak would be the  head turn  servo  interface.   I may have a  hack at trying to   physically bolt on a servo horn to the top  of the  "stem"  so it has proper  splines to mesh with,  or  reworking the model a bit  so it prints with room for embedded nuts  for the tightening screws to thread into.. I melted in my own for now, but if it thrashes  on a reset  of the programming  it could still slip and rotate further around, as happened to me at first before I tightened it down.    

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Nelson Bairos wrote 01/31/2023 at 14:01 point

@redpawFX Sorry for the super late response. Glad it went well. As far as the rotation servo goes, I've had the same issues and am working on an update to better address the issue. Stay tuned, I'll post an update here and on Thingiverse.

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sbbbugsy wrote 12/24/2021 at 04:06 point

Any chance that you will make this a kit?

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