I had one about a thousand years ago when I was a kid. It had a 3" dia. x 1/4" thick brass disc mounted in the center of a 3/16" steel shaft about 3 1/2" long with both ends sharpened to points. The outer ring was 3/16" diameter brass formed into a circle just large enough to let the disc spin in it without touching it, with a cone shaped hole on two opposing sides that the ends of the steel shaft fit into. On one end of the steel shaft, half way between the brass disc and the pointed end there was 1/16" diameter hole though the shaft. You could put a peice of string through that hole and wind it and wind it, and wind it---Then holding onto the outer ring, pull that string for all you were worth. The disc would spin at approximately one zillion RPM and you could then balance the thing almost anywhere and it would stay there till it slowed down. It was painted red. What else do you need to know.---Now---Go and build one!!!