FYI, we tested a couple of design revisions of our TPU tread for SDS Mk4(i) billet wheels at last week’s STEMley Cup & Overtime Sunday events. The photo below shows 3 versions of the tread after about a dozen matches:
Left: The design we used in the 2024 season, with solid rims (which often delaminated)
Middle: A design with larger nubs, 60 degree overhang angles (we were thinking maybe the larger nubs would wear less)
Right: A design with similar size nubs, 75 degree overhang angles, but without the solid rim.
We were happy with the performance at STEMley, and we’ll probably use the version on the Right again in 2025, as long as there’s no plastic (lexan / Polyethelyne) elements to drive over on the field.
For all three versions above, the treads are printed as a continuous ring tire (without a split). The split you see in the photo comes from cutting them off with a knife after use. We also found that the performance and wear was about the same whether the treads had infill (4 perimeters with a 0.4 nozzle) or solid (6 or more perimeters). Each tire takes about 12 hours to print on our Prusa mk2.5 and uses about 100g of filament, costing ~$2 to $3 per.
We found that the continuous treads can be installed really quickly by the method shown below:
- place the tread on the floor
- align the billet wheel over the tire, and inserting one corner of the wheel into the tire
- insert a large flat head screw into the opposite side of the tire, under the wheel like a shoe horn
- step slowly onto the high side of the wheel at the same time as the screwdriver is pulled to stretch the tire over the wheel. Done right, the tire pops onto the wheel pretty easily.
Native Onshape files for our most recent TPU tread design can be found here: CX24 TPU tread Mk4 V1 Onshape File