i am looking for a pattern to make a drum carder...
https://www.instructables.com/id/Drum-Carder-for-spinning-wool-and-other-fibers/I made this one for $50 ($25 in supplies from a home store and $25 or so for the carding cloth).
Yes, but it's almost not worth it to do so. Even if you make the carder yourself, you still need carding cloth, and that costs almost as much as buying a drum carder.
Actually, a drum carder cards wool. Wool combs comb wool. It is two entirely separate types of preparation. I think there are plans available on-line for making a drum carder--maybe by David Bryant?
I imagine someone has. Indeed.