[jasikpark]

i only know from learning about it, but round manhole covers prevent them from falling through the hole by consisting of a curve of constant width. Another example is the Reuleaux Triangle which is a viable shape for manhole covers. https://en.m.wikipedia.org/wiki/Reuleaux_triangle

[mikeash]

The problem I have with this question is that it’s based on false pretenses. Plenty of manhole covers are not round.

[JoeAltmaier]

Cool! I didn't know this was a thing, but I came up with the same solution independently when asked this question.

It also makes a wheel that has a constant tangent from the ground (not a constant axel point) as it turns.

[jasikpark]

not exactly a great logic question