If anyone has done this with any success, I would be most interested in some photographs - etc. I have a 12 ft farm windmill available. I have been considering this for some time. These windmills generate a HUGE amount of torque --- but, they don't turn very fast. You also have to control the tail to set it off-axis when it does start to over-spin a bit. What is that rate??
As I have considered this, it seems that it makes the most sense to somehow transfer the spinning power to the ground below the tower somehow. Maybe you use the traditional up-and-down pumping rod to connect a coorisponding cam and flywheel on the ground. Or, maybe you install a low RPM high volume hydraulic pump at the top, and then use a hydraulic motor to spin the flywheel on the ground.
The flywheel would serve as a speed stabilizer, and would also provide a large circumference surface against which to power the generators/alternators. For a consistently windy environment, it seems you could pull a fair amount of power from such an arrangement. You just have to be very careful to gaurd against losses in each stage (oversized hydraulic hoses, etc.), smooth bearings, etc.
My primary interest is to retain the classic "look" of the rural windmill -- while turning it into a productive player on the ranch.