I designed this tread jig back in February of 2022 for our SDS Mk4 modules. A similar design would work for most treaded wheels of this size. I made it using 3/8" thick polycarb, because we had a scrap piece of about this size and it was the same thickness as the tread and the WCP drill bushings that we used as well.
I was told that I needed to make the black tread holes slightly further apart than blue tread, so I added 1/16" between each. We’re choosing to keep it, but it felt slightly too loose, so if I were to do this again I would reduce the current C-C by probably 1/32" for black tread. For blue tread, move the c-c in about 1/16", and shorten the overall length correspondingly in both cases.
Solidworks download
Parasolid File
Some notes with regards to retreading wheels:
- We considered this of importance because worn tread directly impacts on-field performance - as the diameter and traction changes, autonomous and odometry are also affected, and your ability to push other robots can also be limited. Considering the cost of swerve, all money spent on our treading process was worthwhile.
- We swapped tread before each comp, however, in all cases the tread wear was not terrible - in practice at home, we usually went 2-3 weeks of heavy practice before needing to swap tread
- Across both robots we probably swapped tread around 7 or 8 times in the course of the season - every 3 or so weeks in practice (three times on practice bot, once on comp bot) and once per event on the comp bot. We swapped a few more times over the offseason
- In our experience the blue tread needed to be replaced much sooner
- We ran black tread - we bought a 12x36" sheet, cut it to length (11.22"), and then cut it into 1.5" strips. We got 22 strips out of it, which was enough for the season. The whole sheet cost $62, which comes out to $2.82 per wheel.
- We bought an extra set of four wheels and bevel gears - I would recommend this, because it allowed us to change the tread on the entire drivetrain very quickly (under 10 minutes with no practice), but I doubt it’s really necessary.
- We switched all the bolts to torx drive because we had issues with stripping
- At the beginning of every day of comp (and the day prior to leaving) we did a full examination - verifying all the bolts were tight and closely combing over to make sure nothing was showing unexpected signs of wear or damage. This included making sure the tread on our drivetrain was still in usable condition, and would be at the end of the day.
Thank you for reading! Let me know if you have any questions.
