.....at : www.youtube.com/watch?v=TTbeawIkDeo (http://www.youtube.com/watch?v=TTbeawIkDeo)
A "common" pendulum is a long,suspended body , whose lower end moves to and fro in an arc when subjected to gravity , but the multitude of possible physical pendulums ...can differ in peculiar shapes from what is ordinary.
In my opinion the self-motion of a gravity powered device is due a "certain" pendulum , also...
Al_ex
.....at : http://www.dawn-productions.com/videos/mesmerizing-pendulum-waves (http://www.dawn-productions.com/videos/mesmerizing-pendulum-waves)
As you see , the pendular domain is huge (shapes and arrangements) and the game with inertia and gravity is a real challenge.
The cosmic world is a pendular one...a real call to find the basic model for the continuous motion.
Al_ex
You can use the simulator program "Phun" aka "Algodoo" to make great chaotic pendulums.