First Blade Failure on a Darrius Turbine

[ruddycrazy]

Hiya Guy's,

           Well this xmas weekend I've tried my hand at making my first Darrius wind genny. I thought a helix type blade would suit but without doing any research and just going gungho I'm not surprised with the failure. Anyway even with the slightest breeze the blades started but the best I rpm figures I got was 60 rpm then it slowed down Here is a link to the blades and genny I made http://www.anotherpower.com/gallery/bryan/Image000

           The main centre shaft and support legs can be re-used and I'll try some symetrical blades tomorrow for testing, but on research both Ed's and Vawtmans trials and tribulations are my main inspiration behind my quest to make a vawt that works. So I can see a heap more testing happening but this world has a new VAWT fan and I'm proud to say I'm it.

Cheers Bryan

[Stonebrain]

Good work,Bryan

There seems to be way to much twist in your blades.

If you want place your blades spiralwise,I think it's

called gorlofturbine or something like that,anyway,the cordlines

from the blades must be on the circle around the axis.

For the 'gorlof' you should fit the blades on a cilinder

to come to the right shape.Needs a good deal of craftmanship.

Your blades seems nearly paralel with the axis,so they

should be without twist.

cheers,

stonebrain

[wdyasq]

Bryan,

One of the problems Sandia Labs never solved was the torque ripple of a VAWT. The Gorlov style turbine was/is and attempt to solve that and other problems.

In what little literature is available on the Gorlov I don't recall a blade profile mentioned. One would think any good symmetrical foil would work. The Blade on a Gorlov must twist so the airfoil is at or near the same 'AOA" - Angle of Attack at any time in rotation in relationship with the axis. For the arrangement you are showing, I think that will mean 120 degrees of twist.

Another problem may be your airfoil shape. As I understand your post your shape is similar to () - with points on leading and trailing edges. All good known low-speed airfoils have rounded leading edges for a reason.

I'm glad you are having fun.

Ron

[vawtman]

Welcome to the club Bryan.

 Be carefull not to drive to fast or you might go airborn.Nice testbed

 Never tested twisted blades but seems your on the right track.Your using the twisting of the blades for startup.

 I found that with blades shaped for rotation has the wind hit them from the side it pushes them forward nice easy starting no jiggering back and forth.

 Merry Christmas

 

[ruddycrazy]

Hiya Guy's,

           Well after thinking last night I reset the pvc blades up to a gorlov design, when checking with the laser I only found about 1/4" error on the external profile. Here's a link to the second draft http://www.anotherpower.com/gallery/bryan/Image001

 Now if someone ever meets Murphy give him a kick up the rear end for me as wouldn't you know it was blowing a gale this morning but as soon as I got the test genny up the wind stopped and hasn't blown again since. I'm going to checkout the local scrap yards to try and find some larger diameter pvc so I can work on a proper profile diameter.

 Cheers Bryan

 now some folks will now why I call myself ruddycrazy

[vawtman]

Oh goodness Bryan your not ruddycrazy your just having fun and learning has you go sooner or later you will have to add some meat to the blades for torque.If your planning on makin power with them.I think your getting into a savish type with little lift.Have you visited my files?

 The turbine im working on now will be for rooftops.The chinese have a good turbineCopycats.Solwind also increased blades.Everybody said i was really crazy because the solidity would be too high.At least i know now that im not really crazy just slightly at this point.Stick with a meaty straight blade if your going more than a couple feet in diameter.My opinions

 What size is your rotor?

 I understand no two vawt artists are alike and thats cool.

 

[ruddycrazy]

well I took this rig upto the top of the hill and in I reckon 25 k wind it sat there now when I gave it a hand starting it went about 25 rev's then started in the other direction. I'm not totalling convinced curved blades on a vawt is useless my next setup will be a lot more accurate as 1/4" error is too much for me, but that shouldn't stop a vawt. I could put a small movie of it's performance but why bother, my first weekend into vawts was a total failure. But that wont stop me trying I need to find that bigger pipe before the next trial.

Cheers Bryan

[Gordy]

Bryan,

One quick thought, instead of larger pipe how about a 55 galon drum. And cut your blades from that.

Gordy

[hvirtane]

One quick thought, instead of larger pipe how about a 55 gallon drum. And cut your blades from that.

Gordy

That has been my idea, too.

Some time ago I made a small model and draft drawings. The shape of the profile of the blades would be something quite similar as the blades of 'the Lenz turbine' by 'windstuffEd'.

One man not so far from me has been experimenting with a rather similar machine made of metal, but with straight blades, about 1,5 tall and 80 cm wide. With good results...

- Hannu

[vawtman]

Bryan thats the way i started.One idea had the blades with magnets of simular poles to open and close when the blade was moving upwind the blade would force against the magnets and downwind open.Savish and was a failure along with others.

 Just couldnt get nothing to work without a foil.Hang in there bud and best new years to ya.