Anyway, often on driving by, one can see this unit turning at pretty low rpm (maybe 40-70 (guess)).  The shaft goes down into his garage.  This seems like it would be potentially a very nice setup.  One could set it up with a belt (capstan, I want to call it) to run power tools (a la the old east coast shops sited on rivers with a water wheel, which had power shafts distributed around the building, and belt-driven power tools.  There could also be a belt to a gearbox and charging generator with diversion controller for hot water heating and battery charging.  Belts could be interchanged (shopwork when it is windy;  generator hooked up for standby operation).  The rotor itself is probably low maintenance (paint the drums and turntable) until the main bearing went (sizing this bearing in the beginning for the significant weight would seem to be the most important factor in construction).  

Questions I have:\

--would a truck wheel bearing/rear half shaft be the best choice for this, and how big a diameter turntable (say, of wood) would a typical truck wheel bearing handle on the long term?

--If one used a whole rear axle, could one take power off a right angle drive shaft (which would be up near ceiling of garage); or would the differential cause problems with torque transfer?  

--In a high wind area, what kind of spoiler might work (I'm thinking two or more centrifugally actuated small spoiler flaps that deploy above a certain rpm;  and larger flaps that deploy in still higher rpm (or flaps deployed electrically on signal from anemometer using solenoid or the like).  The Johnson write-up referred to by Hannu (I got one too-thanks to whoever found it) said that the Savonius they built at kansas state had problems with governing (essentially self-destructing in a storm).  So it would seem like they could overspeed and fly apart in storm winds.

--What kind of turntable construction would be scroungable or easily constructed?

--What are the problems and pitfalls compared to a smaller savonius (like two-4 opposing half-shell drums on a vertical shaft).  It seems like failure of the center bearing could be fairly catastrophic.

--It seems like the advantage would be very high torque (which would not keep one from using a gearbox to run a generator as well as tools).

Just fantasizing, but seems like a straightforward design that could be incorporated on a new construction garage (built to handle the unusual weight)-maybe cinder block sides and large purlons in the roof center to hold the bearing assembly.