While researching kinetic sculptures for inspiration to employ in my DWC (Digital Wind Chime), I found that it may be very useful to have components with full 360 degree rotation. Rotating components can be visually appealing, can react well to wind, and work great with accelerometers — three great advantages for application in my DWC. For reasons explained a bit later, none of the kinetic sculptures I ran across use electronics throughout the rotating components. The obvious hurdle would be the wires and how they would get wound up as the component rotated — preventing free rotation.
This is a 3D concept I made earlier today. The red box represents the accelerometer which will measure the orientation of the rotating component. The body of the rotating component is rendered in wireframe so you can see inside. The cylinders are ball-bearings and they are key in this working.
Ball-bearings allow rotation around an axle with little resistance. They work great for rotating wind-driven components, but I also took advantage of the fact that the inner rim, outer rim, and the balls inside are all made of metal (which of course conduct electricity). These parts are all separate and moving, but I can use them to complete a circuit because they’re always in contact.
After doing the 3D sketch to confirm my logic was strong, I set out to build a prototype to test it. I had some ball-bearings from a pair of rollerblades and made the axle out of an ink pen’s shaft (after some sanding). I drilled a small hole for a wire to fit through and carved out a notch for it to sit in, but still be exposed to (and make contact to) the inner rim of the ball-bearing. With the wire in place, I slid the ball-bearing onto the axle over wire. To confirm connectivity, I taped an LED (taking the place of my accelerometer) to the outer rims of both ball-bearings. When I actually build the Digital Wind Chime, what will be attached to the outer rims will be a mass designed to move easily with the wind with the accelerometer placed at the center of rotation.
And here it is lighting up the LED with free rotation.
While I’d call it a success, there are still issues. If I spin it fast enough, it will break the circuit — I haven’t confirmed whether this was due to the internals of the ball-bearings ceasing contact during quicker movement (a potentially significant issue) or whether the wires of the LED disconnect due to inertia (something that wouldn’t be an issue in the final project, as i’d permenantly affix them to the bearings). Either way I’m not too worried — I don’t expect any part of the DWC to move that fast and can do things to reduce that possibility as well. Another potential solution would be to use all-metal bearings (the ones I used for this prototype have plastic walls). Regardless, more extensive testing and prototyping will be conducted.
