The Benesh Profile Savonius

[warpsta]

I have wanted to build this for some time, but never got round to it...but now it's developing. I got the idea from Picoturbine http://www.picoturbine.com and I am much indebted to them for providing these plans (http://www.picoturbine.com/pt250-blade-plan10A.pdf). I am also indebted to Mr Alvin Benesh who holds the patent on this design. A big thanks to Hugh Pigott for giving me inspiration nd good links, Hugh's website is here (http://www.scoraigwind.com/)

To quote from Picoturbine,"This design obviously seeks to improve the lift part of the Savonius blade by making the shape closer to a true air foil. Another advantage of this design, which is mentioned in the patent, is that the long, flat area of the blade is very easy to construct from low cost materials. Benesh claimed that his tests showed this blade profile has a Cp of 0.37, which compares well with some of the best horizontal blade designs. We do not know of any independent confirmation that the Benesh blade profile actually can achieve a Cp of 0.37, and frankly we have our doubts based on theoretical grounds. Our own tests are not yet complete, and will in any case not be definitive since we lack funding for the sophisticated equipment required to perform a conclusive test. However, we do feel, based on preliminary results, that the Benesh blade profile achieves a Cp somewhat better than that reported for simple barrel style blades. Our current estimate is 0.28 when optimally loaded."

Here is a picture of the end piedes:

[kurt]

 warpsta to post pictures here you have to size them under 150 KB and less than 640 x 480 pixels or they will be removed. and please post your pictures as a comment to this diary instead of spreading them out all over be courtous to others and let them have some front page time as well.

[Norm]

Yes, most of us are quite familar with the 250

pico turbine...I've made a couple of these on a

smaller scale and they work quite well...I plan

on making another just large enough to spin a

small stepper motor....the 1ft.x 3ft. didn't

quite make it...so maybe 1ft.x 5ft.

Probably after the swing project and the modified

pop bottle HAWT project. Too many projects..LOL !

                    ( :>) Norm.

[gizmo]

I made one of those a couple of years ago, just to try it out. It's always running, even in the lightest of winds. http://www.thebackshed.com/Windmill/photos4.asp bottom left of page.

I've been calling it the Sandia Savonius, my mistake. I would tend to agree that this design may be a lot more efficent tham most verticals, but the large sheet area has stopped me making a larger one.

Glenn

[warpsta]

They are just under two feet wide, each blade set is 3 feet tall. This gives me an aspect ratio of 6:1

[warpsta]

Thanks for the help Kurt

Here is a blade set with the wire on, ready for the fibreglass. These blades are just under 2 feet wide and each blade set is 3 feet tall, giving me an aspect ratio of 6:1

I'm using the threaded bar to stretch the mesh out so the mesh is taught, although the leading edge is still less than perfect. The holes that the rods pass through will be used to fit balancing weights.

[warpsta]

I'm not sure about how far the fibreglass shouldcome along each side of the blade, I have an overlap but it is not as big as some of the others that I have seen. I don't know if that will make a difference or not, although there is probably an optimum.

Here is a picture of the assembled blade standing upright.

[warpsta]

These blades will mount on to the bottom bearing and hub assembly which came from a scrap car, any advice on cleaning this lot and corrossion prevention would be gratefully appreciated:

[margusten]

Hi warpsta,

I made my first mill by picoturbine 250 plans.

Unfortunately made some mistakes and now this windmill is out of service:

You have to balance Your windmill blades!

In strong winds my mill shaked like space ship going to warp speed.

In one windy day generator belt went off and blades had nothing to slow down them.

So this picoturbine 250 proto entered warp speed and destroyed by wind.

Second important thing - there is poor wind on ground.

You have to build it on something 10 - 20 metere high.

[feral air]

I can't wait to see it finished and in the air.

I'm kind of curious how much the rotor will weigh when completed though. There's always talk about this or that design's efficiency but never anything on weight and how that affects things.

It seems to me that using fiberglass sheets would be easier/better than doing the fiberglass work yourself. Known weight, even thickness, smooth...something to think about for next time.

[electrondady1]

take your rotors to a brake shop and have them ground flat

 it will save a lot of problems later on.

if you use decent mags on those rotors it should make good power .

don't be surprised if you need more swept area to get out what it is capable of producing.

it may be wise to build in a method of adding additional vanes.

[warpsta]

I intend to construct the alternator using the two discs pictured, they have a diameter of 24cm. I intend to mount 12 neos, N38, per disc, they are 2.5cm x 2.5cm x 1cm. I intend to use 9 coils of 100 turns each, one in hand. My wire is 20awg (I think) so I'm aiming for higher voltage, lower current.

If I manage to achieve a tip speed ratio of 0.8 then I estimate that this mill will spin at 8 m/s in a 10 m/s wind, or 152 rpm. If I connect the windings in star I calculate that I will get 25 V ac @ 30Hz and a rectified voltage of 24V dc.

Does this sound about right to you?

[finnsawyer]

A nice idea, but it may not go.  Around here it is illegal for brake shops to grind brake rotors thinner than minimum specs.