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Forum Index : Windmills : savonius rotor,Monash uni, Aust

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human64
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Joined: 14/05/2007
Location: Austria
Posts: 2

Posted: 01:31am 24 May 2007

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Im a new viewer so please bear with my lack of knowledge...I have seen a photo (Renew Mag?) of a S.rotor that purports to be able to spin faster than the airspeed of the wind..it looked something like an egg beater: profiled airfoils around a central spiggot. Possible connection with country Vic and Monash Uni PhD student??? Have also heard of helicoil style ...does anyone have any info on the above?

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5116

Posted: 02:24am 24 May 2007

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What you have seen is called a Darrieus. Yes they do spin faster than the wind, around 3 to 5 times faster from memory. They have a problem with startup, some need to use an electric motor to get them up to speed before the lift of the foils can provide enough drive to keep the machine going.
I think they are cool. Use Google to look up darrieus windmills, and check out this site for an explaination of how they work.
http://purrfectcatshelter.org:8080/James/darrius/

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
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AllanS
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Posted: 04:34am 25 May 2007

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This one is much better looking.

brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1548

Posted: 07:44am 25 May 2007

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Hi Allan S ,,, so what other than say: "this one is better looking" do you have to say ??? .

Bruce

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Gizmo

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Posted: 08:10am 25 May 2007

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That one Allan pointed out has a cool looking video. The Darrieous windmills have a problem with torque pulses, as the windmill rotates the power output goes up and down, and this shakes the structure. But in the video the windmill is on a tall free standing tower with no wobble that I could see. The twisted blades must even out the pulses.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

AllanS
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Joined: 05/06/2006
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Posted: 10:54pm 25 May 2007

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brucedownunder2 said Hi Allan S ,,, so what other than say: "this one is better looking" do you have to say ??? .

Bruce

I want one!

As Gizmo said, the helix evens out the torque curve, stops harmonic vibrations, and also ensures the blade cuts smoothly into the wind.

The price tag is an issue. A Dutch version called a Turby rotor is quite similar, and also expensive.

Making the helical blades would be a challenge for the backshed tinkerer, but I'd love to try.

A thought. Why would the blades have to be curved? Why not use 3 straight blades set at some angle to the vertical? That would be piss-easy to make, since the blade profile is both symmetrical and constant. Edited by AllanS 2007-05-27

RonS
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Joined: 19/06/2007
Location: Australia
Posts: 18

Posted: 02:29pm 19 Jun 2007

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Some years ago I remember seeing a Darrieus rotor on Rottnest Island (Just of Fremantle in W.A.) that had a Savonius Rotor inside it at the bottom to start it up, presumably.

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