I use that style for the fields wind generator. They are actually pretty well made. Just have to change out the rotor to make it work at low speed. Think I get around 5 amps out in low wind, have seen 40 in high winds.
That's neat.
I can see why people like them. They're easy to work on and work pretty well. The internal regulator is a bit of pain when trouble shooting, but they've got the little tab to full field them.
I took apart another one I had, bench tested it, cleaned the slip rings and its working for now. Made sure the belts were tight. Thanks Frank!