i went and built an extractor this winter, all sst constuction. now i am trying to come up with the best way to regulate the speed of it. right now i have a pair of pullys/shivs that reduce the rpm to about 325 max, but i have no way of ramping it up/down. i have been looking for a used vfd because they are so $$ but i was wondering if anyone had used a mechanical clutch to allow more speed control, and if so what kind and where could i get one?