Choosing vanes for low speed DIY Anemometer

Gildasd

Gildasd

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Hello,

Before I modify these vanes, maybe someone has a better idea;
This is a DIY anemometer that costs less than 10$, made from scrap alloy, a 4€ toy and Uni resources.
It's tuned to feed a DC signal into a Arduino and works great, but it's minimal starting wind speed is too high.
Note, I'm measuring relative wind speed, not absolute!
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I was thinking of replacing the half ping pong vanes with something resembling a toilet roll cut in half length wise.
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This will damage it's accuracy in the 10 to 26m/s range, but I don't care, I'm more interested in variations in the 1 to 10m/s

If anybody has a better vane shape idea for this usage, I'm all head vanes (ears)!
 

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Before going to a Savonius style rotor, I'd say the first thing to do (IMO) is to get the rotating mass down as low as possible AND make sure the resistance to motion is minimised. This may need better / different bearings etc.

Best of luck
 
The hub and arms are at their 3rd iteration:
The "skin" is as thin as the printer can, the skins are separated by a honey comb to make a mini monocoque.
The only way to go lighter would be unidirectional carbon, for very little gain.
Can't do lighter than ping pong balls!
The motor is crap and is all I can afford. But it also means the magnets are weak, meaning low magnetic drag...
Etc.

I'm starting to think the angle of the vanes is wrong...
That the plane of the half sphere should intersect the center of rotation.
By attempting to create more "start torque", I might have inadvertently tuned for high wind speed.
Must test!
 
Changing the angle of the vanes has wielded some improvement.

The (highly scientific) testing method was:
A large table fan was set level with the anemometer and the distance was slowly increased till failure to register.
Version 1: 82cm (original, left)
Version 2: 88cm (new, right)

So a noticeable and repeatable improvement.
The two anemometer were near identical in a test before the change of vane angle.
But to improve even more, I still think the vanes need to be bigger.
 

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http://www.walmart.com/ip/Jumbo-Table-Tennis-Balls-Pack-of-12/33455419 ??
 

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