This small roller is a perfect third point for a
small, differential drive robot. Using a ball caster provides better
performance than just having a part of the robot scrape the ground. And,
unlike regular caster wheels, a ball caster will not override your drive motors
and steer your robot off course. This unit is made entirely of plastic
and is therefore very light. To mount the ball caster, just drill a
0.390" hole in your chassis and push in the roller.
For a slightly larger ball caster, see the Tamiya