I saw a program on tv about the Challenge Wind Mill And Feed Mill Co. They were one of the first companies to build wind mills in the states. They made an impressive double header that actually has four rotors. The two main rotors were 32' in dia. They were hooked up about 12' apart. It reminded me of a farris wheel. It had the Two 10' rotors that were in between perpendicular to the big ones. They controlled the yaw of the machine. When the wind would hit the 10' rotor, ether side it would turn an axle with a worm gear that would turn the main pivot. So if the wind changed and hit one of the smaller rotors it would turn making the whole machine turn so the larger rotors would be directly in the wind. They used it on top of a three story grain mill. The mill ran machinery on all floors. The Co was in Batavia, Ill. They ended up with about four other commercial companies in the same city. They claimed that if anyone could out power their mill they could keep it. With the same size double header machine. The down fall was the wooden blades didn't last long, and electricity was made available for the factories. This machine had more than 1,000 blades on it. They were spaced about 2-3 " apart. I wish I could find a picture of it. They actualy made 45' dia machines, but the show was on the restoration of the 32'. The large rotors spun opposite of each other. It was painted white with the outer five foot red. As far as wind turbines go I don't know.
