.....of a possible gravity powered device , at : www.youtube.com/watch?v=hesfXBcgV0s
This is a simple "Magnetspiel" : two fulcrums (stabile,mobile) , three heavy points/masses , two sticks/levers and some "hidden" spare parts (battery+magnets).
If we take off these unseen components , we can play inertia and (unbalanced) gravity , only.
To make it self-running , in my opinion...we need a minimal "attachement" and modification , nothing more...
Al _ex
.....with a natural continuous motion model , at :
www.youtube.com/watch?v=uGBANgbRkws
...and a concept pattern for imitation , at :
http://en.m.wikipedia.org/wiki/File:Palanca-ejemplo.jpg
Al_ex