.....intended to be self powered by gravity , as a lot of proposals on paper, long time ago , at :
www.orffyre.com/mt.html
Playing gravity and the CoM unbalance of a gymnast .at :
https://en.m.wikipedia.org/wiki/Wheel_gymnastics
Playing a continuous gravity unbalance due to a battery "assistance" , at :
www.theswingingsticks.com
Now : why not playing CoM due to a (continuous) gravity unbalance , only ?
Al_ex