It can't happen even through gear reduction. One of the laws of science: Energy can not be created or destroyed only change form. So it could never produce more energy than was used to produce the energy in the first place, to get it to run only it's self you would have to have no gravity, put it in a vacuum, use superconductors to take care of resistance "resistance causes heat and heat is energy" use brush-less and stator-less motors and generators so you would have no friction. I'm sure that NASA could do it but not us Earth bound folks.

If you are looking for free energy go wind or solar, I like the idea of the biodiesel generator.

Thanks for the fun topic
Shaun & Effy