Getting the base right is quite a balancing act, you want to keep it compact and quite low but too compact and too low and you run the risk of the sphere over balancing and coming off the base.

This can NEVER happen. This is bad!!

The problem could be that people over balance their spheres… like an adult sets it up and adds a counter balance to the top half. He then puts his child in the seat but since 100 kg is missing from the bottom of the sphere it’s now top heavy and over it goes…

I guess its possible to figure out this in Inventor… the center of gravity view should be a start….

Screenshot 2014-08-14 22.07.43Screenshot 2014-08-14 22.08.27