Armature Design

To start talking about the unique armature design for Billy I’ll have to go back to where the project started. I initially created Billy as a character to test an idea for a way to more easily lip sync a stop motion character. More on that in another post, but it meant i needed to create a character with a big head and a big mouth. So i started with very rough sketches in a sketchbook before starting to create designs in 123d Design.

I was developing the story alongside this stage and this also played into the design. My sketches are always very rough, but i do lots of them as it helps me to get an idea of how the armature might determine the shape of the final character. The image below is a compilation of various sketches that were spread sporadically on corners of pages in sketchbooks. Not technical drawings in any way but just help me to flesh out ideas for how the mechanisms will (or won’t) work.


I’m not sure if they make sense to anybody other than myself. Looking back i’m not even sure many of them make sense to me. A lot of them were ideas for the mouth mechanism that didn’t work out.

The first thing i wanted to tackle in the build was the mouth mechanism. The advantages of 3d printing helped to offset my inexperience in animatronics as it made vast amounts of trial and error possible.

The video below shows the first lip mechanism i got working, I experimented with various mechanisms and materials for the lips to get to this stage. Initially intending to use stiff wire to move the lips. I wouldn’t get the wire to behave how i wanted so opted for a more solid mechanical design. 3d printing allowed me to easily play around with different anchor points and rod lengths so that I could get maximum movement out of just a few servos. Space in the head is still limited and stuffing 5 servos in was a challenge.

I designed the mouth to have 3 servos at the top and 1 at the bottom. With a 5th controlling the jaw. In order to produce certain mouth shapes for speech, “Ooooooohs” mainly, I tried to design the top middle and bottom servos to produce up/down and in/out movement. Hopefully this is apparent below!

My successes with 3d printing made me decide it would be an interesting challenge to try and 3d print the entire armature for Billy. So a lot of the focus in the armature design had to be around making parts that would be easily printable and strong in the axis they needed to be. 3d prints of this nature tend to be a lot stronger adjacent to the build lines, so I had to make sure parts could be printed in the correct orientation for better strength.

Below are some of the earlier CAD designs, or CAD’s i guess. The first shows an early idea to mount the servos in the chest. Although i scrapped the idea, the top piece remained and made it into the final armature.

The other 2 designs are the 123d design files as they are now. They don’t show a great level of history or progression as I deleted, changed and moved things about as i worked on the armature. This, and my disorganisation in filing, means there is no definitive 3d model of Billy’s armature. Its a Frankenstein of progression.

The pieces layed out at the bottom of the images are pieces that I’ve arranged for printing.


Another challenge came in designing small parts for around the eyes. I was surprised the level of accuracy I was able to get out of a fairly cheap 3d printer but it definitely required reasonable thought being put into the design.

The second picture below shows the rear of the head with the rest of the servos fitted and the other is a bit of a jump to putting the rest of the body together.

The rest of the armature is of less interest design wise. The main challenge was designing parts that would be strong enough to support the armature and endure repeated movement. Luckily, and intentionally, Billy’s a big boned cat so none of the major weight bearing joints had to be too small.

The majority of time spent designing and building the armature was spent on the head. It was the biggest and most interesting challenge and took well over a year in itself.

I did decide to scrap the design completely later in the project, so there will be a post upcoming on head 2.0.

James is the writer/director of Billy Whiskers, scribbling haphazardly on this website to document and share the experiences of making a stop motion animation.


  1. Hwa 4 months ago

    This is truly useful, thanks.


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