As my first construction post, I figured I would start with something lighthearted. This is a simple toy I built while working on a more automated version out of a real hamster ball. I tend to try the kinematics of things on Knex before I invest the time and money of building the real one. This one will roll across the floor if given a push for momentum, but has plenty of room for improvement.
SoMutchToDo 
It’s wonderful. I build other one. You can see my blog.
RC Knex Ball
That’s really neat.