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Forum Index : Windmills : Blades FYI
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nzseagull Newbie  Joined: 07/06/2006 Location: New ZealandPosts: 17 |
Hi Dudes I have been asked to upload some photos of the blades im using..... they are from http://www.ecoinnovation.co.nz/ Nad the link to the blades http://www.ecoinnovation.co.nz/product_detail.php?id=208 At around 35kms wind speed im get up to 35 amps @ 15 volts   
Soon I will be logging the Turbine here as well (icon to be added) i have a Weather Station here as well www.subznz.co.nz |
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makourain Senior Member  Joined: 19/04/2006 Location: Posts: 111 |
your blades arent tapered at the end. why have them square like that? why have them tapered? |
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| nzseagull Newbie Joined: 07/06/2006 Location: New ZealandPosts: 17 |
Hi Well good question thats how they came and the guy that sold them to me would have to be one of the leading experts around here in New Zealand Please note they are made in China and the price was great for what you get Im very please with the blades they are so quite and 550 watts + makes life easy but if you have any way of impoving them would be more than keen to know Out of intrests these blades are bing tested in one of NZs bigest wind farms in the Manawatu and sound like they are profoming well |
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| nzseagull Newbie Joined: 07/06/2006 Location: New ZealandPosts: 17 |
Hi an update on the blades they in in bits after we had 90 kms gusts here at home NZ Taranaki the blades flexed back about 200 mm and hit the pipe and was all over now I have to work out how to make more room may be tilt the mill up 2 or 3 Degs other wise its a total rebuild of the gear It was based on the backshed setup Any good ideas ?? Thanks Bevin |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Wow thats some serious wind. Was the windmill furling out of the wind? If not then the tail was too heavy. 200mm of bend at the blade tips is a lot, furling will fix the problem. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| nzseagull Newbie Joined: 07/06/2006 Location: New ZealandPosts: 17 |
Hi Glenn Yes its furling ok but the gust were major big time all a bit sad really Think it just got hit hard and fast |
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| brucedownunder2 Guru  Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Yep, been there ,done that ------ But I told the insurance man it was hail ,didn't tell a lie ,cause there was hail at the same time. They are good--if smeone can just come up with physical strength that wood offers. Bruce Bushboy |
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Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
Hiya Guy's, Well I do have a heap of 12" pvc I got from work which I've dedicated atleast 2 lenghts to blades and Zubbly from the otherpower IRC mentioned I make a set of 3 metre blades up without a genny attached as a cane test. Now once I can workout a profile it might be worth trying it out as I do have the resources and I intend to laminate 2 pvc profiles together with steel inserts. Man this could prove the longtime worth of using PVC for blades but we'll have to wait 2 years for the results as the position I'll put them will be the best wind spot on my farm but too far away to run cables. Cheers Bryan  |
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| nzseagull Newbie Joined: 07/06/2006 Location: New ZealandPosts: 17 |
Hey guys was thinking of tilting the bearing housing upward 1 or 2 degs to give the blades more clearance from the mast I will need to cut and re weld the bearing but would be easer than trying to extend the shaft some how ? Bevin |
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| makourain Senior Member Joined: 19/04/2006 Location: Posts: 111 |
exact same thing happened to me :( it broke one of my blades in half, but it was on a winch motor |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Bevin, One suggestion is to turn the mill into a downwind mill. No rudder and no furling. If they flex then, they will move away from the mast. Disadvantage: Shadow of the mast. If these are PVC props, then they will regulate themselves through a stall and not overspeed. This is why I believe they will self-regulate. A prop with no twist and no taper. Last time I saw a thing like that it was an extruded aluminium prop, which was sold commercially on the net. You bought it by the meter (~yard). Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
This is an interesting concept, and one I've been pondering for a while myself. Making turbine so the prop is downwind completely eliminates the tail, but so too the option to furl. However, I've been playing about in my head and doodling on paper with an idea of a "nearly" constant speed machine. A number of "factoids" or loosely-releated thoughts: * Leaving the prop blades out of it for a moment, the energy applied by the wind, to an un-loaded machine would quickly make it overspeed and do itself damage. * An over-loaded machine will slow down, or fail to start. * For a given speed (RPM), more power can be extracted if the magnetic field cutting a given number of turns is higher. * The "cogging" effect would be nill if the fixed magnetic field was zero * Glenns (perfectly valid) point that at the end of the day, we're after amp-hours, not peak output - a mill that can produce 10KW, but that doesn't turn at all, isn't any damn use! So, given all this... and the ready availability of quite powerful computers that run on virtually no power, are reliable, have no moving parts and very little mass.... How about making a mill that has electromagnets for the field, and a small additional winding that cam be excited by a fixed magnet in the stator. When there is a breeze, the mill can start turning very early because there is no cogging, and virtually nothing to stop it spinning freely. The secondary coil will produce a small amount of power - enough to power the electronics. When the mill is turning fast enough (the processor can determine this from the frequency), it can start to dump power into the field coils. As the wind speed increases, the mill will also tend to speed up - but by increasing the field current, the magnetic field will increase, thus the output will increase, and the load will help regulate the mills speed! Thus, a "near-constant-speed" - we adjust the field current to maintain our preferred rotational speed! It may be that the excitation winding won't produce enough power to properly power the field windings at these higher levels - so perhaps a (small) proportion of the mills primary output can be used to increase the excitation on the (fixed) magnet. The whole system should be (mostly) self-stabilising. I'd expect potting the controller into the rotor so nothing could fly apart and make it easier to balance. Is anyone doing this? I know it *SOUNDS* complicated, but in reality I don't think it is near as difficult as it sounds. |
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| AllanS Regular Member  Joined: 05/06/2006 Location: Posts: 67 |
Hi Ross, I wonder if the induction generators that Glenn mentioned yesterday would do all that. Thing is, if the mill is spinning twice as fast, I imagine the wind is making available 8 times the power, whereas the generator would only be liberating twice the power. So if you wanted the generator to put the brake on the mill, the revs would still get away from you. With your variable electromagnet field coil idea, you'd need some pretty meaty magnets. Cost might become an issue, as might cooling and weight. I wonder how much of your power the magnets would consume. Just quessing tho. I'm no engineer. I can't help thinking some mechanical way of varying the gap between permanant magnets and the coils might be easier. |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
If the mill was spinning twice as fast, it'd only be making twice the power if the magnetic field remained the same. I'm saying that by increasing the field current, we should be able to virtually balance the extra wind "power" by increasing the mills output enough to balance it. (Does this make sense? I was also wondering about using conventional neyodium magnets as the "core" for the electromagnets, although it would increase the cogging effect) Magnet field is a function of ampere-turns. My plan was to use fine wire and lots of turns, rather than heavy wire and lots of amps. Might be.... I can think of ways of doing it but they all come unstuck because of the magnets tendancies to want to leap at the pole as soon as it gets close! |
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| AllanS Regular Member Joined: 05/06/2006 Location: Posts: 67 |
Hi Ross, Suppose for a given windmill you generate 500 Watts in 10m/s winds and 1000 rpm. And this is the maximum revs allowable. In 20m/s winds, 4000 Watts of power are available. To generate this (and thereby maintain 1000 revs), we'd have to increase the field by a factor of 8. Or so it seems to me. Again, I'm no expert. I agree that mechanical decogging etc seems tricky. |
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Saaremaa Newbie Joined: 10/12/2005 Location: AustraliaPosts: 13 |
Here's an Australian site I haven't seen before: http://www.southcom.com.au/~windmill/ Talking about blade design have a look at the simple metal blades at : http://www.southcom.com.au/~windmill/14ft_alston.htm |
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| nzseagull Newbie Joined: 07/06/2006 Location: New ZealandPosts: 17 |
Well been looking hard into the blade cleance problem and look like what they do is tilt the blades backwards 1-2 degs that will sort the problem have found a few wind tubines that do this to keep the weight in the center bevin Ps so with the cutting disk |
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