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VAWT fiddling started...
DamonHD:
Well, goodness! I have something that turns quite well: a lungful of air has it turn at least 2 or 3 times. Any most of it should survive rain, though is otherwise quite fragile.
And, through ham-fistedly running out of other alternatives, the bearing is at the top, with the whole device hanging down from a 'sprung' pillar. A very small gen could fit in there at the top of the post, with wires running down the post.
I'll take its photograph 'planted' in my garden tomorrow, and see how long it takes to fall apart.
Then I can think about a real VAWT generating my usual milliWatts, when we get any breeze at all...
In any case, I'll see how quickly this one rotates.
What's the relationship between rpm, windspeed, and other design parameters for a simple Savonius VAWT? (I'm gonna Google anyway, but I'm sure that you guys know it off by heart...)
Rgds
Damon
wooferhound:
I made this Vertical Turbine in a rather unique way. It's been hanging in the yard for 3 years now and it's always spinning. Never went past this point in the design, and never tried to make power with it. I think it would work really well with a shroud.
http://www.fieldlines.com/story/2003/12/1/122243/608
feral air:
Sure, I'll chime in...good of you to think of me and my, uh, experiment...
Hanging it like that doesn't really work unfortunately. When I hung my pb-vawt from a (crude) u-joint the swinging motion took up a lot of the wind's power and it looked like it was slowing the rotation every time it swung back. It's now got top and bottom bearings and spins much faster/nicer.
I think a good-sized weight at the bottom would help a little if the weight wasn't being spun. You might be able to use a couple of magnets as bearings for that part.
If you plan to trying this out on a larger scale and more permanently then consider the stress on the bearings over time. Maybe bike wheel hubs would last a few years...that's what I'm using on my big one and I'm crossing my fingers.
If you go with gearing I think 1:10 is about right. When I hooked a radiator fan motor to my pb-vawt the ratio was 1:5 and I got a tickle-on-the-tongue for output - not quite the bite of a 9v battery. The vawt was spinning around 36rpm or so, so the motor would've only been spinning around 180rpm...
With a 1:10 ratio, when your vawt hits 100rpm the motor will spin at 1000rpm. That seems decent. If it's smaller and faster then maybe 1:8...I dunno, it's variable and needs to be done on a case-by-case basis, I think.
This came out longer than I thought it would...I'm just glad I'm not the only one with the bug!
DamonHD:
Ben, thanks for those links. I had already seen them, and my current pathetic prototype borrows from them and others.
Next thing I'll be asking you where to get the magnets in the UK! B^>
Rgds
Damon
ghurd:
Is this optimism, pessimism, or "Heading you off at the pass"? I don't know.
I won't put any more time or money into a small VAWT. A 40cm diameter HAWT is cheaper, easier, and I got at least measurable power.
I certainly wouldn't bother building it dual-rotor PMA!
It is probably best suited to an 8V stepper motor for LEDs or AA nicd/nimh.
Meaning TomW's 'yard art' or a useful "educational toy". Don't be offended. TomW is a realist looking from the perspective of powering a household instead of powering a digital camera.
It will be big fun. It could be usable, in a small sort of way. It won't cost much (with a stepper motor).
Build a similar HAWT, be it similar in cost or swept area or whatever.
It will show why nobody has a proven commercial 50+W VAWT.
Ed might do it, but that is a completely different animal.
To summarize, slap a stepper on it and be happy. :-)
G-
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