Quad bar

[vawtman]

The hbar and 2 bladed hawts have vibration problems at high speeds no matter how well balanced the blades are.The advantage of adding blades to the conventional hbar would be lower wind startup(for those that have that problem)and smoother operation at higher speeds(my problem}.Im thinking more airfoils has diameters increase the better.Why not it would easy to add the extra blades?

[wdyasq]

Sandia labs could never cure the "Torque Ripple" of the VAWT stuff they built.  They spent millions of US taxpayer dollars.  Some of them were mine and were spared becomming beer and sent down the drain with only a headache for memory.

I'm glad to see others trying to make VAWTs. It means my tax dollars are no longer necessary for research.  And, I don't have the funds to properly research it.

Carry ON!

Ron

[vawtman]

And I will.Thanks

[windstuffnow]

  This is simply my opinion, I've built the 2 bladed darrieus and as well a 3 bladed unit.  Personally, I didn't like either as a fixed wing.  Afterwhich, I started playing with the articulated blades or cycloturbines.   They all seemed to work fairly well with the exception of the speed at which they ran.   With the articulated blades I was able to control the speed a little better trading speed for torque.  They all had a vibration problem in certain winds and each seemed to present it's own problem in a different way.   After building several of them I decided to put them to bed and work towards a similar goal but in a different way.  The first couple I built I had a difficult time getting them to run and actually produce power.   They ran ok but slow ( below a tsr of 2), once I realized what I had done wrong the third took off and ran at a tsr of around 6.   I'll have to tell you, once you get it dialed in they go like a bat out of hell and sound like some kind of turbocharger kicked in.   Once it reaches that "tricky spot" between just running and making power I guarantee you it will scare the hell out of you.  Watching the larger one run, you could see the blades changing shape as the speed increased or decreased which lead me to changing the design a bit on later versions.  Without constant attention and controls, no matter how well built they are it is going to fail at some point.  A 5 lb blade traveling at 300 mph can do some very destructive damage.  A runaway turbine in a 60 mph storm with a 4ft diameter will be running at around 2550 rpm or a blade speed of 360 mph.  

  In ending, if your looking to put up a machine that is reliable, low maintenance and safe... the darrieus isn't the machine you want.

.

[vawtman]

Why not stupid is forever and ignorance can be cured?Just a thought.Sorry but until you build one how would you know for sure?I could care less about Sandias problems.Just because Sandia cant figure it out doesnt mean everybody else is stupid does it?Oh my goodness thats scary......vawtman

[vawtman]

Hi Ed.I followed those projects on your website very nice and thanks for the comment.Its nice to hear from expierience.Thanks

[Tom in NH]

I just finished the horizontal rotor arms and this weekend I'll start building the three airfoils for my tri-H-bar vawt. It will be patterned on Ed's Lenz2 design. It will be  fairly large, 84 inches diameter, 72 inches of airfoils. Only now, Ed, you're scaring me. Is the super high velocity vawt to which you allude your lenz2 machine? If it is, I better make my wings stronger than I originally planned! --tom

[thefinis]

Don't know exactly why but an odd number seems to help with the vibration problems 3 seems to do the best. It may have something to do with the downwind blades passing in the wind shadow of the upwind blades and the torque pulses evening out due to blades being in different quadrants of the circle. A two blade lift vawt will have both blades at the no power spot each time the blades are at the 3 and 9 o'clock positions. A quad will help as it will make the interval between pulses smaller and lighter but it will still pulse. The h-bar design will also have the tower shadow to deal with on the lower half of the blades each time they pass thru the turblence created by the tower. Downwind hawts have this same problem.

I believe that the odd numbered ones will still have some vibration problems and the speed/rpms at which it happens will depend on the diameter of the mill, the balancing and the wind speed. Most of us have no way to perfectly balance the mill so they tend to be like a car tire that is off balance, some speeds it runs fine but at certain speeds it gets a vibration. Hawts don't have near the balance and shadow/turbulence problems that a vawt does as they have most of their blade weight near the hub and see the wind as a fairly constant force on the blades.

I am waiting on an anemometer, test tower and warmer weather to try out your blades vawtman but decided to put them on 6 ft arms so the solidity would be low enough to (I hope) get the tsr to 3 but still self start. This may cause the camber to be off as it was set for an 8 ft diameter not a 12 ft diameter. I'll post results after it is up for testing. It is still hard to believe I built an h-bar when they and the Darrieus seem to have the most stress problems but if I can get it to work well it can go on an old windmill tower. I personally prefer the idea of a shaft thru the middle and bearings top and bottom with at least 2 support arms per blade. It has more drag but just seems better suited to handle the stress loads.

Speaking of tsr vs solidity here is a chart I find helpful.





The lines are max and min suggested ratios. I know that the regular formila for solidity is cord x length x # of blades vs swept area but I really think that for a vawt it should be [(cord x length) + (thickness x length) divided by 2] x # of blades vs swept area. If you look at an S rotor you will see that at one point it has 100 percent of the area covered by blades but at another point it just shows the thickness of the blades to the wind.

Finis

PS To finsawyer you were right my brain must have slipped a gear on the other thread. When you use the same blade on a longer arm it decreases the solidity and increases the tsr so all things except power don't stay the same like I was mistakenly saying.

[windstuffnow]

  Hi Tom,

   No, The Lenz2 is a slow running machine.  It runs and produces good power at a lazy tsr of 0.8 nothing real dangerous about it.  It will however runs quite fast in high winds ( no speeds near what the darrieus runs ).   As with any VAWT it's alway good to have a secondary control to stop it during a hard storm ( winds 50-60 mph or higher ).   My roof top has been in winds up to 60mph without any major problems but it will pick up the typical VAWT vibration when its in high winds.

   Post some pictures of it when your done!  Love to see them!

.

[windstuffnow]

  I only posted the cycloturbines on my site, the smaller ones I had played with.  Those are safe to a certain degree but still need to be controlled in high winds as with any VAWT.  I didn't post the fixed wing darrieus projects because I really didn't want to encourage people without some knowledge of the forces their dealing with to build them.

  I dont believe a small one is that dangerous as long as its built properly but larger models can easily get out of control very fast.  

  Jack Park sold a book back in the 80's that has alot of information about them and others he called "hybrids" as well as information on the HAWT's.   I believe it was called the Windpower book. The book is out of print now but I've seen them listed in ebay's half.com area where people were selling used copies of them.  Very informative and quite interesting read.

  I've seen people build up a machine with little reguard to it's actual structure.  They'll grab the main brace with their hand, give it a shake and say something like "Now thats strong".   Well, its quite obvious as mere humans we're not going to bend steel with our bare hands and the amount of force given in the demonstration using the "shake it" technique won't overtax the structure.  But, the force of Mother nature can and will tear it apart like a toy if its not built correctly.  I tend to give the credit to mother nature and build them as if my life depended on it.  Quite frankly, it can!  These are not toys, if you don't know the strength of materials - find out.

  I'm not trying to scare anyone from building them, simply understand the forces your dealing with and do your math.  The darrieus can be a neat machine if its constantly monitored and well cared for.  

.

[SparWeb]

Guys, it's worse than you think!

Problem #1

In a Darrieus turbine, at no time are the blade forces in balance.  The advancing blade is always seeing more relative wind velocity than the other, and the lift forces are therefore higher.

Problem #2

Due to different relative wind velocities on the blades, they are also never at the same angle of attack.

Problem #3

Due to #1 and #2 the direction at which the lift forces are applied there is always one blade with more mechanical advantage than the other.

Problem #4

As was pointed out above, it's more difficult to balance with all the weight of the blade concentrated at the outside radius.

Problem #5

Moment of Inertia is a property of rotating objects.  Apart from its effect on speeding up or slowing things down (which isn't really a safety issue), it has a strong effect on the energy stored in the rotor at a given RPM.  A typical HAWT with 2 blades has a lower moment of inertia than a VAWT, because the mass of the blades in the VAWT is concentrated at the outside of the radius (whereas most of a HAWT's mass is near the hub).  When (not if) something fails, there is more energy unleashed on the innocent bystander.

Problem #6

Similar to #5, the structure of a HAWT (especially a H-bar Darrieus) wants a slender arm.  These spindly things must absorb the energy of all the things listed above.  On the other hand, the HAWT's hub is the beefiest part.  Tapering the tips is both aerodynamically and structurally efficient.

None of these problems are resolved by changing the number of blades.

Unless you are sure that you are competent to safely and reliably overcome these limitations, for whatever gain in captured energy, then step back and find someone who can evaluate the loads and the safety of the machine.

I'm an engineer myself, and when I saw how my 1.2 meter machine behaved, I went back to the math I did before building it.  Seeing is believing, and it was time to take it down.  Particularly when I think of how my 5-year-old likes to watch it run.

Think about it...

[ffoegw]

Noticed on my first ever vawt which had blades/sails with the trailing edge attached to the spoke with bungee that centrifugal forces started to throw the sail outwards and expect this reduced the rpms.

Don't know what might happen with the torque.

Articulated blade?

Gonna have to take a closer look at your site.

I think that even a hawt could be dangerous if/when it throws a blade.

From those kind of tower heights it could go for miles.

Regards

Geoff

[vawtman]

HI Steve

Ive had no problems with problems 1-6 to date other than slight vibration at windspeeds greater than 25mph.The 8x8 runs unloaded in 30mph wind and the blades look their going backwards.Here in Wi windspeeds greater than 30mph occur maybe 2percent of the time.Yes it will have to be monitored during storms but thats no problem.

  Now the advantages

1. Generator and gearing at ground level
   
2. No high tower needed and the tower can be made very beefy
   
3. Easy to inspect and repair if needed
   
4. No tail to find wind direction
   
5. Would be easy to lock down during storms
   
6. Blades are silent
   
   

 Im presently drawing up a 16x16 for the final design which will extract 4 times more power at givin windspeed.My neighbors like watching it.

[vawtman]

Ed I remember when I first tested the blades using a 2x4 rotor with shelf brackets attached to the blades just to see if it would start in low winds.I was glad to turn around and see the bracket all twisted up.I appreciate the last sentence of your comment.Thanks

[vawtman]

Finnis,Boy you have been spoiled down there this winter.Whats you temp probably 60 degrees.A Darrius turbine is the eggbeater type with thin blades that must flex and break over time probably.The Hbars blades can be made stronger and shaped for rotation like yours are.Im still struggling with the gen and going to take off some mags on the 5hp and test.Should be a good fit for the 16ft.I think the 5hp has set up now could easily control rotor speed in high winds.

[SparWeb]

How much power are you extracting?  

I'd surely like to build another Darrieus, but I've stepped back from my design and realized that I'd have to start almost from scratch.  My first was not safe.  Preferring to build a productive machine, I'm building a HAWT.

[windstuffnow]

  Actually the darrieus patent covers pretty much all the VAWT's that use blades standing upright.  That covers the eggbeaters, H-bar type and includes the cycloturbines using the same layout with articulated blades.  Either a very smart man or a very clever patent lawyer.   Even the Lenz2 will have a reference to his patent as well does the Ropatec and many others and yes your's is included ;o)

.  

[windstuffnow]

  The Darrieus patent is 1,835,018 for the VAWT unit.   Also, he also patented a little talked about "wind motor" that has some very interesting construction... 1,820,529

 .

[vawtman]

Ed I have no intent to patent anything at this time and more than likely never will for the cost involved.That process is crazy has I found before with an unrelated project.Just helping others who want to ween from the power companies.Thats all.

[thefinis]

Hey it didn't get to 50 yesterday and was in the low 20's last night but it did get to mid 50's today. Sad part is that most of the trees had already leafed out due to 90's last week and I don't know how far back it will kill them.

The h bar can be built to a fair degree of safety but it has all those forces acting on  it. It just scares me. I would rather grab a pipe at both ends and try to keep it steady than grab it in the middle and try to hold it. It will fit well on a tower just wish I had a way to auto furl instead of manual brake.

Good luck on the genny. I'm going for a brake hp reading till I find the right setup for me then I'll try making power.

Finis

[vawtman]

The idea so far was to design a reliable turbine that could survive swirling winds and low speed start.The gen part is going to be tested soon with different conversions I worked on over winter.According to Wind4regs hbar caculator posted a few months ago.An 8x8 turbine in a 12mph wind would only be around 400w.Well see.

[vawtman]

Hello Finnis

It is a scary sight watching them spin in the begining I have to admit.I would run underneath to slow it down.Has time went on I realized it could hold its own.The gen will control speed.Thats the tricky part Im working on has you know.Please dont skimp on the rotor.Make her tough.I dont think we saw 50 degrees up here since last october.Good luck and have fun.

[thefinis]

Jack's book was what got me started in this direction back in the 80's. I keep several pages copied out of his book in my files. I sent my copy of his book to Costa Rica for some peace corp folks trying to build a wind machine up in the mountains years ago. Times are a changing he would have liked the PMAs that are being built now. The Windpower Book can still be bought off the internet but I think you're right that they are all used books.

Toys? My tools are my toys and it really can't be stressed enough that if you want to know how your are doing on building a wind machine you need tools to measure wind, rpm and power production. Wind is so fickle that while it may be blowing 15 mph in one spot you can walk 50 ft over and it is just blowing 8 mph due to blockage. 10 ft up and it may be 18 mph. This is something that has been posted over and over check your site for wind flow before raising your machine. An extra 10 ft on a tower or 100 ft west may make the difference between usable wind or a failed project.

Anyone who builds a wind machine should expect to lose one every once in awhile. Even the areomotor windmills can't survive all the storms. One way to teach folks wind respect is to carry a sheet of plywood out in a 15-20 mph wind. Yee haw hopefully it won't hurt too bad.

Finis

[vawtman]

Hello finis

 Are you planning to set her up three bladed?Im thinking if your going to 12ft diameter you should add a blade or two.

 Im wondering if someone built aneometers using the hubs Dan sells here?

[CG]

If I am telling you something you already know then I will apologize in advance.

Here in the UK we invested quite a bit in H-vawts, building some pretty large machines, before the govenment pulled the plug. The man behind it was Peter Musgrove, and he late came up with a method to furl them. If you fix the blades to the crossbar by means of a hinge, and if you have more blade below the crossbar than above, then centrifugal force will throw the blade into a horizontal position and in a sense furl it. I can remember Musgrove on the TV in the 1980s being interviewed with small H-vawts whizzing round in the background and the blades being thrown out like the swings on a circus roundabout. But I think he later found that the H-vawt was more or less self regulating.

[rotornuts]

I don't know if I personally would add blades rather than make the blades proportionately larger.

Mike

[hvirtane]

Has anyone of you tried

MTM Scientific, Inc

Aluminum Airfoil Extrusion pieces?

http://www.mtmscientific.com/airfoil.html

Is it possible to build strong

blades using those?

- Hannu

[vawtman]

Hi Mike

  I agree that wider chords definitely help startup and low wind performance.The thought of the extra blades was to increase the low wind performance even more and help balance things more at high speeds.Im trying to extract has much has I can from low winds.

[vawtman]

Hello Cg a couple questions for you.

Do you know why the gov pulled the plug?

How large was fairly large?

Where his turbines under load?

  Has far has hinging the blades for furling I think it would give them an easier

opportunity to either shed the blades or damage any hinging method applied.Im thinking and hoping a properly designed gen could control them.Also you would need a

brake either auto or manual in case of gen failure.You also need to be a weather freak like I am.These are complicated machines and think thats why people just give up on them?Im told I have to much patience,but I think thats needed with these.The

advantages are there.Thanks for your reply.Vawtman

[rotornuts]

As well am I. If you were to take a Vawt that has three blades with a 6 inch cord and a 3 foot span(experimental size) and add another blade of the same size you will have increased the area of the lifting surface by 30 percent. If you were to instead increase the cord by 4 inches to 10 you will have increased it by 66 percent and in addition you will have a blade that is far more reactive in low winds.

After hundreds of hours of searching the net and reading pdf's galore I've come to the opinion that more is not better for low wind harvesting.

Just my opinion though

Mike

[CG]

Vawtman,

The answer to the first question is the plug was pulled by the Conservative government because they were never much interested in renewable energy, they also pulled the plug on wave power, this all happened in the 1980s. There was also structural failure in one of the machines.

The second question can be answered by going to www.eurowind-uk.net and clicking on the history of vawts option. There you will find photos of all the usual suspects, savonius, the large Canadian eggbeater, Windside, and three pictures of the UK      H-VAWTs; they are probably the largest of this type ever built.

Eurowind is a company dedicated to developing H-VAWTs but I,m affraid it is also a company going nowhere fast. The site is well worth a visit, though.

I have no preference for any type of wind turbine, it is just a hobby for me, and what ever gives you fun and satisfaction is ok by me. But I do believe that for all its drawbacks the H-VAWT has at least two good points for the DIY turbine developer. One is the carving of wooden blades; it must be easier to mass produce a blade that has no twist or taper and is symetrical. The other advantage is in gearing. Fixing a generator to the mast and gearing it up must be easier than having it yawl about, as it would do on a HAWT.

Hope all of this is of some use to you, and best of luck with your turbine.

[vawtman]

Mike

  Im going to add a couple blades just to see how it works.I also think a fixed blade

Hbar will self furl at a certain speed.How did yours react in high winds?I have a little one with 2ft airfoils with a 16in chord with a 4ft rotor.The rotor is a wood 2x2 with just 1 shelf bracket attached to the blades.It has survived 60plus winds and the rpms stayed around 120rpms no load attached to it.If these turbines are so self destructive it should have blew apart.You cant build much weaker than that.

  I havent had the guts too let the big guy go yet.I did notice that the rpms dont increase much from 20mph winds to 30.In high winds with 3 or 4 blades and wide chords the blades would try to stall and protect against overspeed.Would you have an opinion on this.I know im going from one extreme to the other.Thanks

[rotornuts]

I don't think the h-bars are dangerous. I haven't built an h-bar style over 26" in height but I went up to four blades. Four has the best starting power, three had the best average performance but two obtained the best rpm and I believe as a conequence had the best power at speed. I think three is the maximum needed for a vertical. If you consider wind shadow from the upwind blade from about the 7:30 to the 4:30 position a three blade rotor least blocks the wind from reaching the rear blade at the point where it is in a position to make power. four blades always block the rear blades when they least need it and two blades has a similar problem but not nearly as bad by any means.

I want to build a two blade but with a cambered flying wing style blade. If you can imagine a swept back flying wing that is cambered to match the circumference of the unit then you can see how the lead edge of the V is always in the open when it needs to be. That is across the front and the back of the unit. There are several other key advantages but it's a loooonnnng story.

I think your big guy is simply flattening out on the pitch. The bugger with these fixed pitch vawt's is the change in appearant wind as they increase in rpm. You need to maintain a higher angle of attack (increasing with rpm) but the more pitch you set for the power points the more drag you produce for the into the wind portion of the trip. I favor large rounded leading edges like ed's machine because they have the best ability to fake extra pitch with only a small tradeoff in additional drag they also do the best job of "flipping over" to produce lift on either surface.

These of course are my thoughts these days but are subject to change as I learn more. I have been in the more is better camp but as I set out to prove my theory correct I wound up disproving it to myself. I even went to the far side of the spectrum and built a single blade Hawt with a really wide cord at 30% and a high TSR and it worked really well aside from the nagging lobing effect you get from having the power produced on only one side. You can have a look at that adventure here:

http://www.fieldlines.com/story/2005/2/23/32738/6596

See my diary for the other installments. I haven't dumped the idea yet but it needs some more serious consideration in the counterbalance department. I have a plan but it's on the backburner as I've come to be fascinated with verticals.

When you think of solidity in the horizontals they say about 10 - 20% But I see that as a figure good for common designs. If you decrease the number of blades you decrease the frequency and as a consiquence you can increase the cord of the remaining blades by an amount greater than the area lost by removing a blade. Alot of people argue that you increase drag with a larger cord and that's true but, like you, low wind speed performance trumps all for me and there are several reasons the extra cord width is better at low winds. Also you don't really have to look at solidity as a function of the circuference of a vertical like you would the area of a horizontal because it's really the frontal area that matters.

Well enough rambling for now. In short I believe the fewer the blades the better but from a functionality standpoint two is the least I can fiqure out how to do except for a bi-cambered single blade savonious style which my helical was supposed to be till I put a twist in it.

Verticals will have thier day if we keep working on it.

Mike

P.S. You sould also consider the diameter Vs. hieght issue. I believe that at least a 1:2 diameter to height ratio is favorable to put more blade into the wind without sacrificing as much rpm.