[Richard Wallace]

My simple minded calculation of stress on the 4" wheel in question:

The wheel's outer section ("rim") is about 5 mm thick, 25 mm wide, and 320 mm long. Its volume is about 40 cc. Assume its density is about 1.5 g/cc so its mass is about 60 gram or 0.13 lb.

At 9000 rev/min, the "rim" has ~4400g centripetal acceleration, or ~570 lb. centripetal load. This stress acts on the spokes and is divided equally among them, at least until the wheel loses symmetry by deforming. So each spoke takes one-eleventh of the centripetal load, or 52 lb. That spoke stress is born by the same cross-section as the rim, or about 0.2 square inch, so the material must withstand ~ 260 PSI.

Neoprene yields somewhere above 500 PSI. How much higher? Probably depends on the durometer.

Please, will a real mechanical engineer check this for me? I know it ignores stress-rise in corners, for example. Those will be more significant for the AM design than for the tear-drop spoke flex-grip rollers we've bought from McMaster-Carr.