NXT LEGO roller ball

thingiverse

This is a third wheel attachment for any two-wheel powered robot. Print it with supports for the top part, as the bottom piece needs to be trimmed off from the ball's underside. It also functions as a fidget spinner and comes in various scales. NXT_Roller_CH_V6.stl includes a cut-away base support for the ball, but if this support fuses too strongly to the ball, reduce your extrusion setting. In any case, the rim still requires supports. I've included an STL file without the base cut-away, allowing you to print the roller ball and rim with your own custom supports entirely.