An Affordable Wind Generator You Can Make Yourself: The Blue Max

(Page 4 of 4)

May/June 1985
By the Mother Earth News editors 
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A second adjustment at the cable eyebolt changes blade-frame tension, which relates, again, to the distance each blade's surface is drawn past center. Furthermore, the blade tip twists as the cable is tightened, which enhances high-speed operation . . . but too much tension can crimp the blade frames and distort the tips beyond the plane of the rotor, both undesirable situations. In practice, a moderately stressed frame is ideal because it's taut yet allows enough slack in the blade fabric to cause "ballooning" at the tips as the rotor approaches its upper RPM limit, which has somewhat of a braking effect.

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The fender-washer governor weights constitute the third means of adjustment. They're fastened near the trailing edge of the blade-frame mount; the more you add, the sooner the plant will upshift.

Finally, high-speed blade pitch can be set by adjusting the stop bolts in the hub. We found a blade-frame angle of 19 degrees from vertical (measured at the hub end) to work best, but because of the varying degrees of workmanship — and air density — that will affect each home-built windplant, it'll most likely be necessary to experiment not only with pitch, but with the other variables, as well, to tune your machine to local conditions.

Specifications and Performance

Output: 350 watts maximum (at 26 mph)
Start-up wind speed: 7 mph
Charging wind speed: 12 mph
Shutdown wind speed: 32 mph
Total weight: 117 pounds
Tip-speed ratio: 3.56
Rotor diameter: 14 ft.
Rotor swept area: 154 sq. ft.
Rotor solidity: .11

EDITOR'S NOTE: For those who might not feel entirely confident of their ability to construct this project even with all the information given here, a set of step-by-step building plans for the windplant — detailed with illustrations and photographs — is available.

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Comments

  • JAMES 7/1/2007 4:05:06 AM

    please send me information on cheap rear blade , designed for road
    grading& mintenance... pull w/ a 2" ball h. ( pick up or
    similar), gracias , atentamente , JAMES.

  • Tom 6/21/2007 12:56:42 PM

    I have a copy of first design wind mill. Is up graded versin better
    and does it not use threaded pipe to assemble! I have my own
    machine shop! I can turn all parts myself. But, has anyone use a
    differt alternator than the gm one shown in piture. I would think a
    dyno generator would work better! It has no brushes and it turns
    easyer. The dyno generator comes on kabota tracktors. Check your
    local tractor dealer for a used one. Usally they just need new
    bearings installed in them. Most dealer replace the hole thing an
    through it in scrap barrel! Oh, some of them look like a water
    pump, but, only have a water fitting on them! So my basic question
    is is upgrade of wind mill w/o threaded pipe! Thanks

  • edgar_p_tan 5/8/2007 3:48:12 AM

    Hi, I read your BlueMax windmill but I can't see the drawings or
    diagrams? Regards, Edgar
    Mother Responds: The illustrations are in the Image Gallery at
    the top right of the article, under "Related."

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