On Sat, 4 Jul 2020 08:24:18 -0700 (PDT),
wrote:



The Plexiglas could also serve as the upper mount for an axle.
--
pyotr filipivich

There can't be any axle above the rotating platform, because you have to be able to look from one side to the other, right through the center.

Bicycle wheels may not be the best choice. They're intended to take a
force orthogonal to the axle. You're asking it to take a parallel
force. One bearing is going to take the load and the other nothing.
The force is also at the edges of the race. Not ideal, to say the
least.

Would it matter if there really won't be much weight on it, other than the wheel itself (I wouldn't even keep the tire)? I can use really lightweight materials for the platform and the cylinder that sits on top.

Weight is your friend. The more weight the more rotational energy
stored. The energy used (friction) is nearly the same, at the same
RPM.