An "odd" pendulum...

[iacob alex]

.....at :  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

[iacob alex]

.....at :  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

[TinselKoala]

You can use the simulator program "Phun" aka "Algodoo" to make great chaotic pendulums.