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Forum Index : Windmills : Single blade windmill
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| davef Guru  Joined: 14/05/2006 Location: New ZealandPosts: 499 |
On NZ TV tonight, some ex-F&P guys in Dunedin (F&P recently closed the plant down) have developed a single-blade prop system, aimed at home-use. Evidently, they end up with a self-furling system. I can see how they can statically balance the prop with extra weights hanging off where the other 2 blades would go, but wouldn't they have a problem with dynamic balancing? Could someone enlighten me? Thanks. davef |
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GWatPE Senior Member  Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Davef, A single blade will place alternating mechanical stresses on the bearing assemblies in the generator and wind tracking mechanism every revolution. I use a single blade propellor on an electric model aeroplane motor. I had no problem with static and dynamic balancing on a fixed arrangement. The main problems are low torque and high rpm. I do see problems at the rotor head with changes of wind angle on the blade, be it from a furling mechanism or wind directions. The most efficient design is a single blade with the counter balance part of the hub. This is the design I have tried. The total blade/counterbalance weight ends up at least 3x the weight of a two blade design. a greater mass is needed to statically balance the blade. Other designs employ 1 or 2 counterbalances as a pod, about half a radius out from the rotation axis. I opted for mechanical lifetime and medium rotation speed, so I have 3 blades on my mill. This has been discussed on other threads. Oztules has done similar experimenting. Gordon. become more energy aware |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5116 |
I think a single blade wind mill, like a single blade ceiling fan, is just for show and not very practical. Like you say, there are problems with ballance, and it will need to have a high TSR to get enough speed to make the power of a 2 or 3 blade turbine. I wish them luck, but its been tried before. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Thanks guys. davef |
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Steve9R Regular Member  Joined: 24/01/2006 Location: AustraliaPosts: 72 |
hi Dave.. you didnt happen to record it did you ? it'd be interesting to see what they're doing.. Steve |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Sorry, no. There wasn't much about the actual design of the machine as it appears these guys are wanting to commercialise the unit. A very nicely formed single blade with two counter weights and they did a quick demo of putting it into the furled position. I'll pay more attention if and when any further footage appears. davef |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Hmmm, I think you would be able to find that on the TVNZ website? |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
here for the article here for their website "Advantages of a single blade". What are the advantages of a single blade, other than cost? davef |
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Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
The advantage of the single blade prop is that it has the highest TSR (Tip Speed Ratio) of all props. This means it rotates the generator faster than any other prop for the same wind velocity(assuming it's designed correctly). But as advised by Gordon and Glenn it is of novelty value only, a great attention getter and may be just what is needed by some poor but imaginative unemployed blokes to get themselves noticed and re-employed. I certainly wouldn't buy one. was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Gill, I have to say that when I was testing my single blade prop, I did get a lot of comments. Most thought the windmill was broken. I did not like the appearance either of a single blade. I prefer an odd number > 1 blades. I also think that the teetering furling system would create dynamic imbalance. The high TSR of the single blade could create tip noise at high power levels. Gordon. become more energy aware |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
[quote]I certainly wouldn't buy one. [/quote] Or invest in this start-up company 
Thanks guys for further attributes of a single bladed windmills. I'll get on with building the tower and start datalogging. davef |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Have read on Fieldlines that Willy Messerschmidt of plane fame had experimented with single blade props. Nature has developed a rotating tree seed with a single "prop", don't ask me which tree it comes from. The idea is for the seed to "screw" itself into the soil. Where are they making the F&Ps now? Don't tell me it is China! 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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| grub Senior Member Joined: 27/11/2007 Location: AustraliaPosts: 169 |
"Where are they making the F&Ps now? Don't tell me it is China!" I have heard that they are going to both Korea and Mexico. |
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