Here is a other robot I made for Solarbotics instructables. The principal is base on the “symet” robot. Symet stand for symetrical/symmetric robot. You have a single motor where the shaft rest on the ground. It moves in different directions depending of the point of contact around the shaft and the ground. In my case I use 3 wheels and one of them is motorized. When the motor is powered, the entire robot spins in circles while moving foward.
httpvhd://www.youtube.com/watch?v=WUCDza0Kz94
If you want to build your own, please visit :
http://www.instructables.com/id/Solar-Powered-Battle-Symet-BEAM-Style/
Here is the embeded instructables. Have fun!
Solar Powered Battle Symet – BEAM Style – More DIY How To Projects