Author Topic: Latest small VAWT attempt with VIDEO  (Read 6781 times)

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CmeBREW

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Latest small VAWT attempt with VIDEO
« on: April 19, 2009, 05:50:31 PM »
Hello again friends,


    Since I already had made the alternator a year ago, and it was sitting under my desk in my bedroom doing nothing all winter, I decided to try again at making a simple Vawt on top of this small trailer hub alternator.  This Vawt is just the common "S" two blade made from 26 ga. sheet metal. It is 2' diameter by 3 feet high. (only 6 sq. ft. swept area is tiny though)


The rest is just 3/4" treated plywood. I intend to paint the galvanized sheet metal brown later.







Here are the two videos. I just put it up yesterday. Haven't got to see what it will do in big winds yet.  I hope for 10-40 watts max.  But who knows. This is a terrible location actually and the winds are coming intermitently from the worse wind direction today.  I will move it to a better location later and re-record it on a better BIG wind day later.(IF it holds together!)


 Winds shown are about 5-12mph I guess.  The Ammeter is hooked in series with the 12v battery.  It is mostly just trickly charging today, with it doing a lot of 2-5 watts.  In the second video, you see it starting out over 5 watts. (.4 amps @ 13v)


http://www.youtube.com/watch?v=eUL4ZhX352Y


http://www.youtube.com/watch?v=ujTfAV4GGC4


But I am almost certain it is still in mechanical STALL.  I need to get more length of wire to try and get it out of stall more or get some little 20 Watt power resistors and experiment with that.  You see the small speaker wire length of wire in the video I am using to try to get more out of stall.  But I don't think it is enough yet.  When I unhook the wires, it free spins quite a bit faster actually.

I'm learning that Getting the right Torque rpm range is very tricky with these Savonious Vawts.


The follow pic is when I had it in my living room before putting it up.

A cheap box fan turned at it starts it up VERY easy from ANY angle and turned it 60rpm.  I think the rotor so far weighs about 30lbs.  But I believe I will add some metal or wood supports on the sheet metal blades to 'straighten up' the blades so they don't boe out so much.  So far I don't see a need for a center rod in the middle, but I could be wrong when the big winds get here again. We'll see.





The diagram below is my Super Basic Theory on the air flow of this Savonious. The invisible 'Positive pressure line' always heading in the positive direction in relation to the center axis is VERY important or it would cancel even worse! The rotor obviously is turning clockwise.


It seems to me, the right side of the rotor cancels about 25 percent of the potential, with say, 75 percent going in the positive (clockwise) direction. Thoughts??




Anyway, It is all good fun and ALWAYS fascinating to see any windmill produce a little power to use later.  I think I will keep messing with this one and trying to improve it , because this Savonious Vawt looks to be the most promising Vawt yet I have attempted.  

I love the looks of these I must say, and I can always put it on a better looking 12ft high pole with the wire inside.  


Any thoughts or questions appreciated!

« Last Edit: April 19, 2009, 05:50:31 PM by (unknown) »

Norm

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Re: Latest small VAWT attempt with VIDEO
« Reply #1 on: April 20, 2009, 04:47:57 AM »
Stove pipe has an interlocking hem that so the

edge already has stiffened edges.

....or you could make a simple sheet metal brake....

(like a board and some c-clamps) bend the edges

over)and you wouldn't need any sticks to stiffen

the edges.

  Make it twice as tall on a shorter tower....

if you have the alternator wired for high current,

connect it for higher voltage? instead ? if that's

the highest voltage mode try charging a

6 volt battery?

  All kind of ideas.....with VAWTs....don't try

to improve on this...just add to it....make it

bigger !

  In the meantime pedal away on the pedal machine

keep them batteries charged ! LOL !

« Last Edit: April 20, 2009, 04:47:57 AM by Norm »

Ungrounded Lightning Rod

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Re: Latest small VAWT attempt with VIDEO
« Reply #2 on: April 20, 2009, 12:29:48 PM »
Two suggestions:

 - Try the Sandia Savonius profile.

 - Put an extra form in the middle to support the blades against bowing and make them hold their shape under load.  (It can be supported by the blades.)  Essentially no air goes up-and-down in a non-helical Savonius design so it's not costing you power (except for the tiny amount of cross section it blocks.)
« Last Edit: April 20, 2009, 12:29:48 PM by Ungrounded Lightning Rod »

Stonebrain

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Re: Latest small VAWT attempt with VIDEO
« Reply #3 on: April 20, 2009, 02:15:14 PM »
Good work,cmebrew,looks fine.


I agree with ulr,some reinforcement in the middle wouldn't hurt.

I think the profile ulr talking about is called 'benesh',somewhat betyter performing and somewhat faster then the classical savonius.

These high rotors allways make me worry about forces at the bearing,with strong winds,hope you made it strong.


A few watts is allready better than most vawtbuilders have achieved :)


Keep us informed about future improvements.


cheers,

stopnebrain

« Last Edit: April 20, 2009, 02:15:14 PM by Stonebrain »

CmeBREW

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Re: Latest small VAWT attempt with VIDEO
« Reply #4 on: April 20, 2009, 03:41:13 PM »
Thanks fellas for the helpful comments.


I most likely will try the center support and blade (outside edge) reinforcements in the near future like you suggest.  Today just happen to have some bigger winds and I got to see some more performance characteristics.


It is strange. It must Still be in mechanical STALL, I just can't believe it. It is very frustrating.  I went and bought a 100ft. (16ga/3 wire) today to add in series with the 40ft cord (before the rectifiers) in order to try and bring it out of mechanical STALL and it seemed to help some but not enough.  In one big gust it did do 14 watts for a few seconds and then went back down to 6 watts.  Mostly it maintained only around 4 watts. But today was very windy. (gusts up to 25mph)


So it is still somewhat useful for my small 12v system even as is in this horrible location.  I would say it does 10-100 watt hours depending on the windy day.  But I know it will do better if I can get it a little more out of mechanical stall. (It takes TOO much TORQUE to turn the alternator)  

My little 32" diam. (high solidity) Hawt above my roof did probably twice this today in Watthours. (but it is in a somewhat better location so who knows)


Today I let the Vawt free spin for a few seconds during the strong winds, and it spins much faster and then I hook the wires back together and the ammeter briefly shows over 40 Watts and goes back down fast.


 I thought the 100ft cord would loosen it up and trade some of that hard to turn torque for more speed. It did some. It allowed it to make a little more power. But this 20 pole (3-phase) dual rotor alternator I made sure requires a LOT of torque to turn to even get 1 or 2 amps. Right now, the 12-13v cut-in is about 70rpm.  Its like the amps (Amps seem to be like TORQUE to me/ Volts is like SPEED) wants to raise TOO quickly.  You can't go with bigger diameter to get more Torque, because it will be too slow then.  I need to 'Thin the Torque out' the way it is somehow.


Does anyone know how I can get this damn alternator out of stall?!! I hardly want the voltage drop of a 400 ft cord wrapped up in a big coil.


Maybe I will get and try some little power resistors next and see what if that helps.


-If anyone ever thinks of anything else you think even might help, it would be greatly appreciated.  If I can get it better, I will show another video here


 -Thanks.  

« Last Edit: April 20, 2009, 03:41:13 PM by CmeBREW »

ghurd

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Re: Latest small VAWT attempt with VIDEO
« Reply #5 on: April 21, 2009, 03:13:13 AM »
Those winds from the wrong direction frustrated me too, the howling in the tree tops, and nothing to get my windmill spinning.


If the alternator can be configured Jerry rigged, it will take more RPM for cut-in (120?), but less torque for the same amps.


You said "anything".

I have an unusual idea.  

Try disconnecting one phase.


G-

« Last Edit: April 21, 2009, 03:13:13 AM by ghurd »
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electrondady1

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Re: Latest small VAWT attempt with VIDEO
« Reply #6 on: April 21, 2009, 05:19:45 AM »
"Today I let the Vawt free spin for a few seconds during the strong winds, and it spins much faster and then I hook the wires back together and the ammeter briefly shows over 40 Watts and goes back down fast."


sounds like  p.w.m. is required.


the mill should be made strong enough to live through the strongest winds without load


i don't get what you mean by mech. stall.


i have never seen a savonius with that much of a gap between the halves.

i don't mean the overlap.

 i mean the distance from one half to the other across the center.

it looks like about 30% of the width.

whats the thinking behind that?


as well, whatever happened to that beautiful squirrel cage you made.

« Last Edit: April 21, 2009, 05:19:45 AM by electrondady1 »

Dave B

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Re: Latest small VAWT attempt with VIDEO
« Reply #7 on: April 21, 2009, 08:08:10 AM »
Can you open the airgap and run it faster ? I know little about VAWTs but without having to re-wind your stator or change your alternator design altogether I would think adjusting the air gap might be worth a try. Other than that it seems like the same old match the alternator to the blades to the load routine. Great work, you and Ed seem to be paving the way to useful power with the VAWTs.  Dave B.
« Last Edit: April 21, 2009, 08:08:10 AM by Dave B »
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TomW

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Re: Latest small VAWT attempt with VIDEO
« Reply #8 on: April 21, 2009, 09:13:05 AM »
CmeBREW;


I would agree with Dave on this. My now 8 foot turbine used to have a 10 foot prop that got destroyed. A simple prop swap from 10 to 8 foot gave dismal results until I opened up the air gap to give the prop its head so it could get up to some RPM. After that it performs nicely.


It was a bit amazing how much air gap changed cut in.


Definitely try that first. It is the easiest and cheapest way to alter cut in on an already built unit, near as I can tell. It was advice from DanB so not my idea but it worked beautifully.


Good luck with it.


Tom

« Last Edit: April 21, 2009, 09:13:05 AM by TomW »
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CmeBREW

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Re: Latest small VAWT attempt with VIDEO
« Reply #9 on: April 21, 2009, 03:48:27 PM »
Thanks guys for the ideas.  Sorry If I miss someone's question.


I made another quick Video after work today. Wind was a little better. I made two videos but The better video didn't play right, but this one is OK.  You can see the Ammeter better in this one. IT is doing a fairly steady 4-8 Watts in the video.  I didnt get to watch the Vawt today but for a few minutes, but it did 16 watts during one big gust.  It went above 1 amp several times, but I didn't have time to wait around to video record it during stronger wind gusts:


http://www.youtube.com/watch?v=n-NcM_FGz3o


Yes, I had already opened the gap last year during previous (Humiliating;fruitless;etc) Vawt testing. The magnets are only 1/4" thick and the mag to mag air gap is 1/2" now , and the 12v cut-in rpm is about perfect now. With the 100' cord I just added yesterday (which I will need this anyway when put the pole and mill in a better location away from the house) the NEW cut-in looks to be somewhere between 80-90rpm. (up from about 70rpm)   Cut-in Seems to be good.


So I really would rather not raise it anymore or it would miss quite a bit of Trickle charging in the lower wind days and of course, inbetween gusts of wind.

I think I will try the power resistors next and see what that does. Thanks for suggestions.


I just found out today that the diameter of the Vawt is actually 21" inches. (NOT 24" // So it is actually only about 5.5 sq. ft swept area)


Sorry, but I forgot I had jigsawed off the 'ears' that my previous 16 blade PVC 'Squirrel cage' Vawt had.  BTW, I never could get that Squirrel cage Vawt to work that good at all. Evidently, most of the wind would just go around it and the wind inside it did not do what I had hoped it would.  I will NEVER attempt that type Vawt again.


It seems to me These simple "S" Savonius Vawts has the biggest chance for success.(for a Dumby like me anyway!)  

I am not going to bad mouth Vawts so much anymore.  I can see some potential now-- it's just that they are NOT so simple. Sure would be nice to have a testing wind tunnel and smoker to see whats actually happening with the cycle rotation!

(But of course, there are still a PLETHURA of Vawt SCAMS on Youtube I do NOT believe in the least!! But there are a very few there I do believe in)


Trying to charge into a 6v batt with this Savonius does not work well since it requires even MORE torque to turn and the cut-in is way TOO low.  I tried it. It sucked.

Also, disconnecting one of the phases DOES allow the VAwt rotor to spin faster, but it looks like the power is alittle less actually. (not much less though)


So Who knows. I will keep experimenting and research that Benesh Sandia Vawt rotor and see it I can improve. But I am going to stick with these small "S" Vawts myself.

 I know it is not much power, But even the way it is now, I am happy that I finally got one that looks really neat and actually makes a little bit of USEFUL power for my small system.


-Thanks again. If and when I improve again I will keep you posted.    


   

« Last Edit: April 21, 2009, 03:48:27 PM by CmeBREW »

CmeBREW

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Re: Latest small VAWT attempt with VIDEO
« Reply #10 on: April 21, 2009, 04:24:54 PM »
I also meant to say the 12v Battery in the video is fully charged and so is doing 13v went charging. You can see the Ammeter in the video doing some good .4 to .68 amps. The better video had a little better amps.


I forgot to mention that the sheet metal pieces I used were 3' long by 21" inches wide each blade.  They are not from stove pipe, but rather just normal 26ga. sheet metal I got from a Heating and Air conditioning installer guy.  I just cut the sheet metal with a jigsaw and metal cutting blade (18tpi) and safety glasses and ear muffs since it is very loud. Sharp little metal particles do go flyin everywhere when cutting. Eye googles are even better.


I do not recall how wide stove pipe like Norm mentioned is, but I bet it would be fairly easy to make a smaller Savonius rotor with it I'm sure, since it is already bent in the shape. I had somewhat of a problem doing mine by myself.  This 26ga. is fairly hard to hold in a bend while screwing.


Thinner 28ga sheet metal would work too and you could easily cut that with tin snips, but the rotor would surely need supports and bracing of some sort.

Gearing would be cheap and easier with a flat belt from an Automotic store and round pieces of Treated plywood (since you can keep cutting them until you find the exact rpm torque/speed range you need) .   You can get decent ball bearings for a few bucks ea. from Tractor Supply Co.   Just some possible ideas.    

« Last Edit: April 21, 2009, 04:24:54 PM by CmeBREW »

CmeBREW

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Re: Latest small VAWT attempt with VIDEO
« Reply #11 on: April 22, 2009, 02:52:05 PM »
Thanks Electrondady,


"it looks like about 30% of the width."

Yeah, I was just experimenting seeing what would happen having it more open like that. But it may be costing me some power, so I will try it the other way with the two halves being closer together or 'tighter'.


By mechanical stall I just mean it looks like the generator is TOO powerful for what the small wind rotor can deliver.  Sorta like a little kid struggling to pedal a 10-speed it 10th gear.

Here is a video of it Free-spinning faster in probably about a 20-25mph turbulant gust.  I could be wrong, but It just seems to me I could possibly get more power if I could utilize more of this speed and a little less torque?? Who knows.


http://www.youtube.com/watch?v=cdMLO983lJg


I will keep working on it. Would be nice to get a little more power out of this puppy.


-Thanks for your ideas.

« Last Edit: April 22, 2009, 02:52:05 PM by CmeBREW »

electrondady1

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Re: Latest small VAWT attempt with VIDEO
« Reply #12 on: April 23, 2009, 04:28:24 AM »

you are a more than competent builder so you know how easy it would be to double /triple the height of your mill.
so that it can shrug off any load the alternator can put on it.

if you short your alternator, will it stop your windmill?











 
« Last Edit: April 23, 2009, 04:28:24 AM by electrondady1 »

CmeBREW

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Re: Latest small VAWT attempt with VIDEO
« Reply #13 on: April 24, 2009, 03:30:42 PM »
Thanks again Electrondady1,


Yes, I'm sure the others were wondering why I don't just double up on the height also to keep same speed and just double torque since thats what i've been complaining about. But As I'm sure you all can imagine, it adds much more complexity and bulk (size) to it and requires the strong 'cage' around it to support the bearing on top.


I am really just trying to design a 'good looking' compact smaller Vawt (no cage) that is on a pole with no guy wires, that hopefully no one would complain about in a residential setting.  I think this small size (and thus, small power) is what I am after so I could put up 2 or 3 in different places I suppose.


This alternator Easily holds back this little Vawt rotor in ANY giant wind gust. But I noticed that when stopped, a big gust sways the whole pole even much more than if it were just left running.  So I am still testing this thing to see whats what.  I believe I am having some decent results for such a small rotor. I may be on the right track.  Hopin!


I have an update below. It was windy again today and I tried some different things. See below.   -Thanks again

« Last Edit: April 24, 2009, 03:30:42 PM by CmeBREW »

CmeBREW

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Re: Latest small VAWT attempt with VIDEO
« Reply #14 on: April 24, 2009, 05:22:50 PM »
UPDATE:


I DID achieve the 10-30 watts that I wanted!!!  Yippi!


Only problem is it is a little windier than I had wanted to achieve it. It was the so-called 20-30mph windy day today. In the video below, you will see I just short stop my 5' hawt in the background because the wind gusts were a little too strong sometimes.


I painted the Vawt rotor brown like I said and so it don't reflect the sun anymore which is good. I did numerous changes and tests today.


In the following test, you will see the Vawt rotor turning faster than usual. Since it was very windy and gusty today, I hooked a 6v golf cart battery in SERIES with a 12v battery (Just for the Test!) which allows the rotor to spin up faster to a higher speed 18v batt cut-in rpm.


I like the fact that it was turning faster which actully made the rotor MORE stable in big winds than the lower speed 12v set-up which sways the pole a bit. (which May cost some power--not certain yet)


I liked this higher rpm/voltage set-up Test -- it was quite consistent charging with the turbulent wind gusts--- but the only draw-back is in lower winds (10-20mph days), it would miss a lot of consistent little watts since the cut-in would be too high most of the time.  I also did another 'Free-spin' video, and it goes way faster than this.


Heres the first video:


http://www.youtube.com/watch?v=gyH-cfpG0W0


Another change I had attempted yesterday before this was to make the rotor more like the 'Benesh' Vawt which is wider. I'm not saying it was exactly correct or anything like that though.


What I did was move the two blades outward 2 more inches. This made the over-lap of each blade only 1/3rd over each other (instead of 1/2 lap-over) and so the over-all rotor diameter was quite a bit bigger at 25" diam. with a wider blade swing.


It did noticably worse. It cancelled much worse on the opposing/returning side. It reminded me of some of the big diameter Vawts I had frustratingly tested last year.

I did not like it at all.  You think you will get more torque, but it did not happen that way.  It was only HALF (or less//no consistency of charging)  the power and only did any power during short wind gusts.  


 I couldn't make a video of the testing this way though because it was raining, but the winds were very strong. I watched the ammeter inside.  I did take still pictures of the rotor this way though, if anybody wants to see those ineffective changes.


Rather, I now like the Tight circle (small diameter) configuration rotor.


So I changed the rotor back the way it mostly was exept for a couple changes.  I put supports up each blade (both sides) and put a metal cross support to hold them 'inward' better.  Before this, the blades were boeing outward on the sides. Now I straightened them up.


I also brought the two blade 'halves' closer together toward the center. It made the two halves 'tighter' with each other.  


What I had said about 'Machanical Stall', I doubt is the case now.  

Because I did the following test --- I used a variable power resistor and did some testing with it.  The resistor DID allow the vawt rotor to spin faster (sort of reduced the Torque required), but the power (watts) was reduced quite a lot (half or even more) into the 12v battery.  I don't like that. Forget the power resisters!

But the 100' long run wire is acceptable since I will need the distance and it lets the rotor run slightly faster with little or no loss. (evidently)


So it seems at this point the problem (to acheive even More power) is that this little rotor simply can NOT convert anymore mechanical power into watts the way it is until I can improve it by reducing it's drag cycle or design.


Here is the second video of it in some fairly big turbulant gusts (at the corner of my house) doing over ONE AMP many times today.  This is into a 12v battery.  

It did the brief 30 watts max when I had it set-up with the 18v batt(only testing).

It did 26 watts max when hooked to a 12v battery but was spinning slower and sways the pole a bit.  


http://www.youtube.com/watch?v=ppbV5R1-THo


Anyway, I hope I am on the right track.

I'm sure it did over 100 Watt hours today (Including the windy night tonight).

My goal is to double the amount of power I am getting now.

Whether I do or don't -- It is fun to try!!!  

« Last Edit: April 24, 2009, 05:22:50 PM by CmeBREW »

CmeBREW

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Re: Latest small VAWT attempt with VIDEO
« Reply #15 on: April 24, 2009, 07:02:50 PM »
I forgot this.  The Free-Spin Video.  


Seems like every video of a Vawt I have ever seen on Youtube, they are going real slow-- even free-spinning. Hard to believe you can get any power from those those.


Mine is Free spinning probably over 400rpm in the video in a turbulant 20-25mph, so ya know you gotta at least get something from that!! Because the sides go out an inch on each side, the actual diameter is closer to 23 inches.  


If you pause the video, you can see the supports I added.

You can also see my 5 ft. hawt shut down in the background.


http://www.youtube.com/watch?v=AjUcCiv3Tyo

« Last Edit: April 24, 2009, 07:02:50 PM by CmeBREW »

CmeBREW

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Re: Latest small VAWT attempt with VIDEO
« Reply #16 on: April 27, 2009, 07:10:21 PM »
Another UPDATE: (For any 'Crickets' who might still care)


This first picture is the profile of the Vawt in all the Videos above (It is half over-lap):




The picture is of the bottom that bolts to the hub bolts. It worked OK I guess.  But I wanted to try something more like the "Benesh" Vawt (Below) and so I cut down the arc a couple inches and widened out the diameter to 26 inches:










I think those little wooden vertical supports were causing some drag, so I took them out but kept the steel cross support bars to keep the rotor from boeing out.





Here is the Video in big winds.  It is alot more violent-- and it did seem to have more torque (but a little slower) but certainly would need a top bearing and cage around it which is a lot more work and may not look as good.


http://www.youtube.com/watch?v=4bkWoq2Ffb0&feature=channel_page


It actually sways a lot more than the video appears to show. It may buckle in a giant wind gust possibly. (+50mph)

Notice how it bends the whole rotor and the pole in this approx. 30mph gust.

It only did 30 watts max though the same as it did before. But before (this Benesh change) it did a lot more lower wind/ low power charging and was more stable in big winds without needing the top stabiling bearing it seems.


With a cage and top bearing it MAY have done more power, but this way was slower rpm (bigger diam) and so missed producing some power because now the cut-in was a little TOO high. (aweful SMALL window with these things!)


Who knows , it may have been better this way, but I did not want to make the whole cage and top bearing and so I switched it back SIMILAR to the way it was.


-And so the saga continues...

« Last Edit: April 27, 2009, 07:10:21 PM by CmeBREW »

Bruce S

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Re: Latest small VAWT attempt with VIDEO
« Reply #17 on: April 30, 2009, 08:29:19 AM »
CmeBrew;

Glad to see you're still tweaking it.

Can't view the vid at work but will when home.

Question about the "blades" out past the plates. If you have a windmeter could you grab a reading or two of the wind at the overlap point? Smoke would be perfect to see effects.

I'm thinking that the wind hitting there could be causing wind eddies that are back tracking causing the whole system to slow.


I could be totally wrong , but worth a look.


Keep smiling;

Bruce S

« Last Edit: April 30, 2009, 08:29:19 AM by Bruce S »
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CmeBREW

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Re: Latest small VAWT attempt with VIDEO
« Reply #18 on: May 01, 2009, 04:15:44 PM »
Thanks BruceS,


I don't have a wind meter, but I am actually thinking about setting up a few quick 'Smoke tests' though with some strong fans and a little smoke in a pan behind the fans in my dad's two car garage with the door open. It might tell me a lot.


I also need to do more simple fan tests in the garage using many little plastic 'flags' taped in various places while slowly turning the vawt and observing what is causing more turbulance and 'cancelling' and where.


I still suspect I can get more out of this puppy.

It sure seems that the 'exhaust' part of the cycle is important.('Exhaust' being the wind flowing thru theend of the "S" shape and immediantly being hit by the arc of the next blade)


 The ANGLE of the 'exhaust' may be important, and the SPEED of the exhaust may be important. I have many tests and changes to do yet.

I have changed the positioning of the two blades in relation to each other several times to see what happens.  Eventually, I should get something that works good by the simple process of elimination!!


-Thanks, I will keep trying to get more out of it.

« Last Edit: May 01, 2009, 04:15:44 PM by CmeBREW »

Bruce S

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Re: Latest small VAWT attempt with VIDEO
« Reply #19 on: May 06, 2009, 05:56:08 AM »
CmeBrew;

The amount of testing you are doing is very inspiring. The amount of knowledge your getting is fantastic..


It would be very interesting to see how the flags or even better smoke is moving through the exhaust side of the blades.

I suspect that a small amount of left over wind will be good to keep the mill moving through/into the wind as it tries to extract as much usable force possible.

Using smoke would be good to see the interaction as it get expelled out the "back" side of the 'mill.


I think, not sure, that it should show a kind of push of the wind out with a small eddy of wind to help carry the blades past point where the two blades are neither capturing nor expelling , long winded version of what I'm trying to visualize, sorry if it's not so clear.


Keep Smiling;

Bruce S

« Last Edit: May 06, 2009, 05:56:08 AM by Bruce S »
A kind word often goes unsaid BUT never goes unheard

CmeBREW

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Re: Latest small VAWT attempt with VIDEO
« Reply #20 on: May 08, 2009, 01:49:22 PM »
Thanks for the vote of confidence Bruce!  


I will try my best to do the big fan and smoke test with a video camera as soon as I can. I also think it would show a lot.  

I found two more little videos that I thought were sorta neat because one has a truck going up the side street in the background, and the other one has my father mowing the grass far in the background I didn't even notice before.


http://www.youtube.com/watch?v=X-MH0c5jO0A


This next one is another video of it free spinning with no load.  The only reason I showed the free-spin is so no one can say that the slower videos were actually free-spinning, when those were under load generating.

If you look closely at the bottom, you see my dad mowing grass far away down the hill.


http://www.youtube.com/watch?v=FiS41U-3M8U


Anyway, I opened up the gap AGAIN on the alternator (as TOM suggested) to, in essence, make it 'Wimpier' and weaker (Required Torque and thus Amps rise SLOWER with rpm) and therefore to allow this small vawt rotor to spin faster.  

It may be better this way but I am not sure yet because I can't seem to get the static balance correct at the top of the vawt rotor now. (Arg!!!)


After taking it down and experimenting and changing (different angles,etc.) things about a dozen different times now, the sheet metal blades have bent slightly in various ways and some little small dents.  Now it won't seem to go back to being perfectly centered at the top and so it sways a half inch which is enough to keep it from spinning up to good speed and prevent most power from being made. It can not free-spin 400rpm with it out of balance like that now.  


I may need to put a center support pole now up the middle as ULR suggested to force  it centered. It was easy to center it without a support pole the first several changes, but now the sheet metal is messed up.


It's no big deal though, because I strongly believe I can improve the performance signifacantly now with a design change.  I can reduce cancelling on the vawt rotor blades much more by rivoting a secondary piece of sheet metal (actually aluminum flashing) to the inside of the steel sheet metal making a secondary curve/angle with each blade thereby making all positive pressure angles much better AND reducing cancelling from opposing angles. (difficult to explain until you see it)


I am excited about this change and feel strongly about it.  I learned about this by myself during experiments last year. Basically, the inside aluminum sheet curves are very much like the "Benesh VAwt" curves which flow the air thru the "S" very quickly and with quick 'exaust', which I like that idea since it could allow the rotor to go faster.  But the outside curve steel sheet metal (that is rivoted to the aluminum sheet) goes way out at big steep curves to allow much more positive angle in relation to the center axis, even from most of the opposite returning side. (also difficult to explain without seeing)


-I will post improvements when they arrive!!    -Thanks.

« Last Edit: May 08, 2009, 01:49:22 PM by CmeBREW »