Linkage DANcer

This project was inspired by a small music box my grandmother had when I was a kid. When the mechanism was wound up, there was a little wooden court jester attached to the front face that would bounce and spin upside-down. I always had a lot of fun playing with that and I wanted to make a larger version that people could control and then see the linkages moving as the figure dances.

Instead of a wind up mechanism, the dancer is just moved directly with a rod on the back. I had originally intended to have a crank give it a repeatable motion, but in the interest of time and also for the sake of having a bit more random motion, I opted not to build the extra crank.

I wanted to give it a playful human element, so without wanting to embarrass anyone else, I put my own picture on the face. The googly-eyes were pretty much required from the start.

My hope was that someone who approached this exhibit, if not immediately terrified, would make it dance and play around to see if they could make the figure do anything unexpected. By controlling the mechanism, the motions involved can be traced out.

The arms move in a controlled way due to linkages. The shoulder angle relative to the body is driven by the body position and angle relative to the mounting plate, the elbow angle is driven by the shoulder angle, and the wrist angle is driven by the elbow angle, so the entire arm is defined by where the user positions the dancer's body.

Rather than constrain all of the motion involved, each legs is a set of two unconstrained pivots. The intended effect was to create two semi chaotic double pendulums. On a side note, I went on the internet and verified that the plural form of pendulum is actually "pendulums" and not "pendula", which is also technically correct but rarely used. Unfortunately, the lengths and weights of the leg parts did not allow for much chaotic motion so instead I added a rubber band to spring load the legs apart a bit. This really helped keep the dance looking a bit more realistic but still very strange and fun.