The constant speed idea is derived from the standard aviation term whereby the prop on the engine of the aircraft is used to maintain a constant speed (pre-set by the pilot) on the engine, irrespective of the power settings used.
My idea is based on this idea, (as was employed on the Jacobs windcharger of many years ago) where the prop blades actually are twisted to a coarser or finer pitch (similar to that done in aircraft) as the speed increases or decreases.
As the blades start to turn, say up to about 50rpm, the rotating field will not be energised at all. After about 50 rpm the blades will start to twist, and the mechanics of this will set off a micro switch, thus energising the rototating field (rotor) to a limited extend. The faster the blades turn, the more they become twisted into a coarser mode, tripping more micro's and changing the field strength.
I am fortunate in that I have the blades available as well as a lathe and the now how (I work with them everyday in the aviation game).