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ghurd
Junior Member
USA
313 Posts |
Posted - 19/03/2008 : 16:33:26
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Neat. Reminds me of a ceiling fan conversion, except for not cogging.
If it stalls, make some longer blades. I expect it will stall.
No, I don't know how much longer. I make a lot of blades until one size stands out above the others.
That's why the belt sander gets such a workout.
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ghurd
Junior Member
USA
313 Posts |
Posted - 19/03/2008 : 16:46:33
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Quick math, I think it needs to be about a meter diameter.
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Del
Junior Member
United Kingdom
369 Posts |
Posted - 19/03/2008 : 16:53:12
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Ok Ghurd,
Will keep you posted as to the performance data when I get some wind. It's a difficult unit to bench test as it's the unit that spins and not the shaft. I don't think it will stall due to having the six blades, but we'll see.
PS. Jolly impressed you speak metric !!
Cheers
Del. |
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ghurd
Junior Member
USA
313 Posts |
Posted - 19/03/2008 : 18:24:42
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200 RPM is crazy-slow, even for 6 blades at 1 meter dia.
Maybe the resistance will keep it from stalling too bad?
Anyway, I find it bloody interesting.
I am bilingual. I speak broken-English, and American.
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super windy
Junior Member
217 Posts |
 Posted - 19/03/2008 : 21:49:34
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good work there del, I like the look of the unit, keep us informed of the output.
cherrio, and well donne
super windy |
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MattM
New Member
USA
91 Posts |
Posted - 20/03/2008 : 03:35:21
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You have a nice flat frontal area. I'd recommend extending the blades to the center as close to the middle as possible. This not only give you more blade surface it also moves air off the face whereas now it creates a bubble of slow moving air. The shape of the blade, where you farm airflow on the leading edges of the blade, has a bonus effect when the backside of the next blade hits the airflow and purges it forcibly out around the hub. The faster that air flows through the middle the less air overall that has to move around the turbine.
Go Huskers! |
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Del
Junior Member
United Kingdom
369 Posts |
Posted - 20/03/2008 : 18:28:51
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Hi MattM,
I did think about that actually but I thought the flat area would just create a bubble that would divert the air around - like a house I suppose. The wind doesn't really hit your house it flows over it.
Anyway, as we've got some decent wind today I thought I'd take both my little turbines up to an exposed area on a small hill about a mile from where I live where you can see for miles and miles. The Rutland is a 60W unit so 5 amps was the expected output. On the hill it seems happy to put out 1 to 2 amps and when it blew really hard up to four. I tested it for about a minute and we did see 5 amps once, but even though the wind was pretty strong it seems difficult to get it above 2 amps. Ghurd - I think you may have been spot on with your prediction.
My other little turbine (DC motor unit) I'd bench tested and knew it cut in at about 380 rpm and had a max shorted amp output of 9.5 amps. Immediately I put the turbine up on the hill it was constantly putting out between 5 and 8 amps. I was extremely pleased with that but it's still going on ebay tonight as the Rutland will be a better unit for my sheltered back garden with its low cut in.
I think with the Rutland I'm going to get rid of the six blades and bolt on three longer ones (they will fit on my hub design without any modification).
Cheers all.
Del. |
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ghurd
Junior Member
USA
313 Posts |
Posted - 21/03/2008 : 01:27:46
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Might consider making 8 blades (2 extra) at the same time.
I have a feeling 6 blades will do better than 3.
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Del
Junior Member
United Kingdom
369 Posts |
Posted - 22/03/2008 : 10:14:55
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Thanks Ghurd,
I think I'll have to get back up onto my windy hill with a selection of blade configurations and see what works. I'm actually away from home now for a few days so it'll have to be in a week or so.
My other turbine that I tested at the same time hit 8 amps (probably it's max) within five seconds of putting it into the wind and that had three 50 to 60mm pvc blades cut from 90 degree section. I was very pleased with it's output. So three small/medium blades can transmit that much current.
Ta
Del. |
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ghurd
Junior Member
USA
313 Posts |
Posted - 24/03/2008 : 02:52:06
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I don't think 3 blades will do it with 200 RPM cutin.
6 blades will give it more torque for low wind.
Not sure which will be better, I'm just saying try it both ways.
8A with 55mm blades is impressive (and very windy?). I'd keep that one!
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Del
Junior Member
United Kingdom
369 Posts |
Posted - 24/03/2008 : 10:32:12
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Yeah you're absolutely right Ghurd, I don't think three blades will transmit the torque required at such low rpm's. I think I was talking crap yesterday. I thought about it an hour later and slapped myself!
Yes it was windy to get the 8A with the other turbine but it needs about 380rpm to cut in and rarely get that much blow in my back garden.
Cheers
Del. |
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Rutland generator
