Self Balancing Egg ( Columbus Egg )

This egg always stand vertically once you release it. It contains at the bottom a 5/8" or 16mm metal bearing ball that shifts its center of gravity close to its wide bottom.

I printed it in its vertical orientation with material support only from the printing bed (that is, no material support inside the egg). When it completed to print the internal cylinder I paused the printing, dropped the ball in, and added some glue from a hot gun (epoxy or any similar glue should also be fine), and then