Hi
I have no experience of this but .. .
to create a note by airflow a thin membrane with a resonant chamber is normally required. If you look at a clarinet or wind instrument they use reeds, brass instruments use the upper lip of the player. Spinning tops hum because air drawn in at the centre resonates inside the cavity, before being expelled at the edge, kinda like a mouth organ.
So IMHO you need airflow and a thin membrane or reed to create the sound and a cavity. Sound can be created by cavity resonance, without a reed, blowing over the top of a glass milk bottle, but the conditions for this are not easily set up and are fairly critical, also your flywheel will have to have a very large cavity to get into the audible range, which for maximum sensitivity needs to be around the 100 to 3000 Hz range.
At 100 rpm I don't think there will be sufficient pressure, even at the circumference. Even a spinning top has to be running at speeds well in excess of that.
However I think it may be possible to cheat
By attaching small magnets to the outer part of the flywheel it should be possible to cause a sheet of card or fibreglass to act as a sounding board with a magnet or metal piece attached to it. Alternately, if you make the outside of the flywheel castellated (or just aluminium with steel inserts) you can just use a single magnet attached to the sounding board. Obviously the tone will change frequency with the speed of rotation giving the illusion that the wheel is humming. If the sounding board is tuned to resonate at say 200 Hz this would make the sound fade as the speed reduced.
Just my 2 cents worth.
Best Regards
picclock
