Inventors have proposed plenty of ideas

There wouldn't be any left over to power a car or charge a phone.But what if you just wanted the machine to keep itself moving?Inventors have proposed plenty of ideas.Several of these have been variations on Bhaskara's over-balanced wheel with rolling balls or weights on swinging arms.None of them work.The moving parts that make one side of the wheel heavier also shift its center of mass downward below the axle.