Look at the RPM's of the motor
With wind, you should be looking for lower RPM's
I've been that route last summer
But the day after I bought a "Tread mill motor", (Whole thing for $4.00)
I also picked up a Ametek 30 VDC, (localy, $20.00)
before they were tried, I got on E-bay a 24 Vdc servo motor, ($37.00 w/ shipping)
And a CMI stepper motor, E-bay also was only $0.99, (Shipping was $25.00)
When I got to test flying these motors
Tread mill wouldn't start with ceiling fan blades, (BAD windmill motor){off size shaft also)
Servo motor has flown many times with many blades and wouldn't get
over about 2-6 VDC, (BAD windmill motor, {RPM}).
But,
The Ametek has flown since last fall with ceiling fan blades,
Did loose a set to 70+ MPH winds.
Tried many quicky blades after that and have it back up ceiling fan blades again.
(Only 3 with stock pitch and many 20" long)
This set-up works pretty good on VERY short test tower. (13')
The $0.99 stepper @ 28Lbs was stripped of controls and tested as a AC type windmill
using only the stuff I left inside plus 3 Bridge Rec's to get DC
Testing with a coffee cup size AC motor duck taped shafts together,
got 112 VDC with no load
Tested with 5 ceiling fan blades about burst a dome light bulb and because I was only holding it with meter also about scared me off of windmills, (because learning about how strong a tower needs to be the hard way is UNSAFE to say the least), lol
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