You could use the LEGO Steel Balls as a third wheel on the robot. It is a caster wheel. But this is steel and as we know from basic existence on this planet, where there is steel there is also rust. The steel ball could get quite rusty and this could have an influence on the behaviour of the robot.
- 09 Jan 2018
Rust on the steel ball
Check your steel ball. If it is very rust try to replace it or to remove the rust. If it is rusty there is more traction between the ball and the plastic "container" of the ball.
Building instructions for a LEGO Mindstorms EV3 Robot that we call Five Minute Bot, because it could be build in Five Minutes.