There was a company in Ohio over a hundred years ago that produced most of the wind mills used for pumping water on farms. It was the Heller Aller Co. (sp) All of those old 3 legged metal tripods you see on old farmsteads were made by them. On the top was a propeller in front and a tail in back. There was a lever you could pull that would turn the tail 90 degrees and stop the propeller from turning. I'd imagine you could google Heller Aller and find some info. sail
Most of the homemade wind mills do not put out enough power to measure. Being made of car altenators, you can't get them tuning fast enough to be worth squat. You can buy a decent wind gennie for around $500.00 and change. I did
On our farm way up north, we had Aeromotor, as did most others in the area. I am willing to bet it had a lot to do with regional sales who got what. Most windmill towers are 4-legged. I don't recall seeing any 3-legged ones in the recent years.