A student at Ohio University came up with a lash-up that reminds me of the old Kenner Spirograph toys.
From the article at woub.org:
“Howsare, who was recently featured on wired.com, already owned the two turntables. A few stops at the local hardware store produced the other materials.
“They were just kind of domestic materials, it was things I had at my house,” he said.
The original design required Howsare to spin the turntables manually, but he eventually changed the design so that the machine moved on its own.
It took Howsare two weeks to create the machine, but he says it’s not done yet.“
You could waste weeks tinkering with that thing.