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Induction Motor Conversion.  
The motor I used was a small 1/20hp 240vac motor found at the local rubbish dump. The only problem with it was a stuffed ball bearing.
I removed the windings and rewound with 0.91mm wire. The armature was machined down and some magnets glued in place. I then machined the magnets back to give a 0.5mm clearance. The armature was painted to prevent rust and a new bearing fitted.
I laser cut a propeller bracket and mounding bracket out of 4mm mild steel. The propeller bracket was bent to give a slight twist, and the mounting bracket bent to support the motor.
I mounted the new alternator on a old windmill frame I use for testing.
The blades were cut from PVC pipe. You can get an idea of the profile from the picture, remember you can click on most of the picture on this web site to see a full sized picture
The windmill output voltage was lower than expected, at 6 volts for 400 RPM as tested on my lathe. In the air I've seen 800 RPM and 11 to 13 volts, a little low for charging a 12 volt battery. But output current was good at 6 amps shorted.

The PVC blades were profiled as per the image here.

The image shows 4 stations.

I will either use a auto-transformer to up the output voltage to a good charging voltage, or rewind the alternator with more turns of lighter wire.

The most successful part of this project was the PVC blades. They are working very well and only took about 10 minutes to make with the help of a saw bench and power file.

Update...
I rewound the stator with 0.6mm wire and was able to fit a lot more turns. At 400 RPM the new combination produced 18 volts open circuit, and 3 amps shorted. Back up on the mast the windmill now works like a gem, pumping a couple of amps into a 12v battery in 20kmh winds.