11" BB-8 prototype BB-8 robots

Building BB-8 Part 2 – The Startening

BB-8 presents some interesting engineering challenges. How do you get a robot that is basically a head balanced on a sphere to move around? How do you keep the head from falling off, and how do you move it independently from the ball? How can you make a robot that is a hemisphere on top of a sphere able to express emotions and interact with the world?

Nobody completely understands how the prop builders have made BB-8, so everybody who is building their own BB-8 is figuring it out themselves. The BB-8 Builders Club is collaborating on designs: everybody working independently (including me) is sharing what we learn. It’s open group prototyping, and it’s a fantastic way to work.

The Club’s best guess is that BB-8’s main “body” sphere is 50.6 cm in diameter, and the “head” hemisphere is about 30.0 cm in diameter. If you’re in the US, you can buy plastic hemispheres and spheres from California Quality Plastics; a pair of 50 cm diameter hemispheres will set you about about $500 USD. That’s way too much for me to spend on a prototype, and a 50 cm diameter is pretty big to have sitting around the house. I decided to build my prototype inside something smaller and cheaper.

I poked around for a while and finally settled on a run-about exercise ball for rats, which I picked up at my local pet store. I was lucky that the owner had rats, because I didn’t even know that the bigger run-abouts were a thing. The hamster-sized balls (about 17.5 cm diameter) are too small to work in comfortably–especially with the motors I have sitting around–but the rat-sized balls (about 29 cm in diameter) are perfect. I picked up the run-about for about $35 CAD. And I’m off!

I’m going to try to build the robot only from parts I have on hand. If something seems like a totally weird or completely awesome choice, it could just be because it was what I had sitting around. For example, I wish I could take credit for the choice of control over Bluetooth, but  it was because I had an Arduino-compatible Bluetooth module and couldn’t find my Xbee shield.

Next up, I’m going to dig through my old parts and build a drive for BB-8.