Posted: 06:16am 12 Nov 2005

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I finished the VAWT based on the Lenz 2 design this weekend. Its out in the yard and so far working ok. Only a few feet above the ground for the time being. The alternator os a F&P motor, not decoged. The windmill starts easy and reaches charging current very quickly. Will keep you posted.

Posted: 07:46pm 12 Nov 2005

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Nice work as usual ,Glenn.

Well, just when I thought I'd have a break from building things, ,,oh well., start up the welder !!! lol

Bruce

Posted: 06:52am 13 Nov 2005

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Very impressive, and I can see why it starts easy too...grunt mill there.

Had a chance to test different wing angles yet? BTW, how have you wired your rotor up Glenn?

I still think you should decog. I checked DC voltage on mine prior to decog and after decog....no apparent loss. But the motor was noticably easier to start and turn. I have a few F&P's here now, but only the one decogged. Very noticable difference - imagine you would get a higher charging voltage sooner.

Posted: 09:36pm 13 Nov 2005

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......damn, that's a really good lookin' mill!

Posted: 10:31pm 13 Nov 2005

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We have a problem. Didn't even think of it when I was putting it together.

The thing sounds like motorbike driving down the road, its loud to the point of annoying.

I forgot about the cogging vibration of the F&P. For a normal windmill this vibration is barely audiable. But with the large surface area of the VAWT, it radiates this drone in all directions. Once it speeds up the sound goes away, but most of the time its there, driving me and the dog crazy.

I'll play around with some damping, maybe spray a little foam gap filler into a few corners.

Posted: 12:47am 16 Nov 2005

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I shut it down yesterday. The sound was driving me crazy. Windmils should be seen and not heard. I even tried undoing the hub so it only covered about 20% of the stator. No power and still that god awfull drone.

If I take the hub off, its spins without a noise.

So what to do now. I have a little piston water pump I made, so I'll use the windmill to drive that and feed my header tank. The windmill has lots of torque, so should work fine.

Glenn

Posted: 08:24am 16 Nov 2005

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Two thing I believe will fix that

• Larger wing support beams up to 50mm. A lot of that vibration it being enhance by flex in your current beams. Instead of running them through the wing as you currently have, use some L-channel(angle iron) so your not interfering with the airflow inside the wing.
• De-cog it. You loose nothing and gain a smother operation.

I've noticed you have resisted de-cogging. Can I ask Why? Have I missed something about the effects of decogging? - please tell, I'm curious!

Posted: 10:41am 16 Nov 2005

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Hi Greg.

Yeah bracing may help. but that adds to weight, and its already pretty heavy. The prop weighs over 20kg already, and I made it as light as I could.

There is a small power loss in decogging a stator. I cant recall the exact figure, and the EcoInn.co.nz site is down so cant find the answer there either. But I know the only reason to decog is to help startup, at the cost of a few percent of power. The VAWT with its extra torque had no problem starting a standard stator, so there is no need to decog.

I did unwind the hub to the point of almost falling off. There was only the slighest cog felt as I rotated it by hand, but still this was making a noise that was not acceptable.

The vibration from the F&P is axial, meaning the drive shaft is speeding up and slowing down about 56 times per revolution. On a HAWT, this means the propeller leading and trailing edges will be doing the same, but with a small surface area not a lot of noise is generated. But the VAWT has a very large surface area axially, so generates a lot of noise.

The VAWT would be great for a different type of alternator, like a servo motor to DC generator. It does have a lot of startup torque, so I think it would drive a step up gear box or chain drive easily.

Glenn