Another short project but I think it’s worth it to document for the future!

I’ve been casting my own urethane wheels out of Simpact 60A for the past year or so but I’ve never tried casting tread. All my molds have been CNC milled and one piece so adding tread would be unreasonable.

An example of my previous cast wheels can be seen on the baby Uppercuts! They work great so if the tread doesn’t work out I can always fall back to smooth ones.

Now with the power of my DLP printer I decided to give treads a shot.

I designed the mold such that the cast tread could just flex over the mold when being ejected.

The assembled wheel mold consists of 3 DLP printed pieces and clamps a printed wheel center.

When I’m done casting, I unbolt the top washer, push out the bottom blue part of the mold, and then push the finished wheel out of the green mold in either direction.

The first tread pattern was a bit dramatic and looked like fish bones. I also did these without a vacuum chamber which results in some air bubbles but those won’t matter much in combat robots.

I decided to copy the tread pattern from Uppercut’s go kart wheels and added some dye.

The blue hubs/pulleys are removable so I can cast many of the same wheel and use them on either side of the bot. In this case, the wheel centers (red) are TPU and the hubs/pulleys (blue) are NylonG.

Fred also sent me a link to some McMaster 40A urethane tubes which Ripto uses so I might give those a shot so I can avoid the annoyance of casting.