It seems that nobody produces a COTS "FRC grade" mecanum wheel in the 4" size range. The recent 4" vs 6" vs 8" size discussion (
here) has made a lot of good points about the benefits of smaller wheels. I'm looking for an offseason project and some custom built mecanums sound like a good challenge.
I've managed to pull together some information from a few very helpful sources. Notably:
- Jester Drive article in the Aim High Behind the Design book
- Pics from team 2865 (here)
- Brandon Holley's post on urethane casting (here)
- Ether's derivation for roller contours (here, direct download link)
After a bit of time in Inventor I was able to come up with a rough draft of a design:
My plan is to machine the hub from a blank of 6061 aluminum and mold all the rollers using the Smooth-On brand of products. I'll first 3D print some rollers, use those to create a silicone mold, and then use the molds to pour urethane rollers.
Before getting started I wanted to post here and solicit thoughts and criticisms from the group. I'll be happy to answer questions on my design, as its really the product of the work of lots of others.