I don’t want to hijack Hummie’s thread too much talking about mold making but the original pattern was a 3D Printed piece made on an Objet Polyjet printer which has much better finish quality than a typical FDM style most consumers use for making parts. The print was sanded, primed, sanded again, and then molded in a high durometer silicone for dimensional stability. I work in the silicone and urethane casting material business (technical sales, teaching, and make all of our tutorial videos) so I ended up helping on the project when I knew I could prevent mistakes. Wheels were the EZ part. Motors, bearings and windings was where Hummie needed to spend his energy fine tuning.