Questions for centrifugal blower guys

Back in the 50s, Studebaker/Packard used a McCulloch (precursor to Paxton) blower that had a unique clutch on it. It would kick in at 3000 rpm. The blower pulley was like the driven pulley on a CVT. As revs increased, the pulley "shrunk". Is Paxton or one of the other centrifugal S/C makers using a a clutch like that? Just wondering...