SNIP

BTW Have you looked into using Delrin (acetal) for your wheel? It
is available in both Balck and natural (a sort of light cream
colored white. and is a lot more durable than nylon.

We need the rosin to stick, and for the material to be completely stable
regardless of the humidity.

Greetings Alden,
I don't know about the rosin sticking, but acetal resin absorbs almost
no water. It is vey stable with changing humidity. In fact, I make
scuba parts out of it and the lack of water absorption was one of the
main reasons for choosing this material. It is a good engineering
plastic and can be used for bearings, knobs, etc.. Soon, I will be
sending out to several people small pieces of this plastic that are
just scrap to me. If you want some let me know. All you pay is the
postage marked on the box. About 4 dollars.
Cheers,
Eric