We built a variant of these during the off season using 60A Durometer Urethane. The CoF with the 60A was approximately 1.3.
We bought a 4ft tube of the urethane from Sunray Inc with an ID 3.25in and an OD of 3.75in for ~40$ off of McMaster
The inner diameter of the wheel was 3.5in, which means we streched the polyurethane .25 inches. The rims were made in halves so they could stretch the urethane, eliminating the need for another method of attachment.
I would recommend about .25 inches between the inner surface and the outer wall, since anything less than that tends to fall off the rim.
We also cut a groove into the urethane so that it sat flush with the edges and increased the surface contacting the carpet.
Benefits:
- Smooth ride, no jittering that the zip tie mount method can produce
- Easy to replace
- Durable
- Can be anodized, and the tread comes in any color. Useful for robot branding.
Cons:
- Expensive
- Essentially Colsons
- heavier, since wheels are aluminium
- LOTS of machine time
Video of base