Savinous Overlap video

[zap]

Heard on the news we were in for more wind so I decided to cut some buckets up and make another VAWT, this time using a 25% overlap instead of 50%.

The 50% one is the white set on the right. The pipe is just keeping them from spinning.





I've got them bolted onto the axles of the wheels and chain is looped through the spokes to help keep em earth bound. Even with about 30lbs of chain... this is what happened with a 50mph or more gust!





Middle of the morning but the gust was so loud it woke me. I think the gust was enough to tip the mill wherein the chain was enough weight to start the left horse over, the gust subsided and brought the mill down between the two horses. Nothing really damaged, the buckets are hot glued to the plywood but it must have really been spinning. I found some good gashes in the turf from all the thrashing about.

I need to find some cheap magnetic reed switches then get some of Norm's Dollar Tree $1 pedometers. Anyone know a cheap source for reed switches or what equipment to look for that might have some reed switches in it to salvage?

Here's some video of todays action  Broad Band video 9.6M

Or for dialup users  Dialup video 808Kb

Just having fun watching em spin!

[Norm]

  You can just use the pedometer as is some cam

or other to jar the bottom edge of the pedometer

make sure the pedometer is the new model with 4

screws holding the back cover instead of 2 on the

older, inferior model.

  Time doesn't permit me to continue more on this

subject right now.      ................later...

               ( :>)Norm.

[theTinker]

that is a very impressive video, i think i might try build one of those, so simple and effective.

[zap]

CORRECTION!!! The white set on the right is the 25% overlap, grey is 50%... sorry it was getting late when I posted that.

[wiredwrong]

find an alarm tech, ask him for a door switch I was able to get a bag full from a guy that worked for ADT just by asking, they look like this...





I have used them in making homemade alarm for truck but think they could be used for rpm counter, I used a small piece of a hard drive magnet instead of the one that came with it

[zap]

Thanks for the tip wiredwrong, I'll have to keep that in mind. I ended up making one out of a spring, seems to work ok for now but it's no where near weatherproof.

[Norm]

  Put it inside of a large drinking straw

small drop of hot glue on the end.

             ( :>) Norm.

[zap]

LOL... I wouldn't want to meet the person in a dark alley that could suck this through a straw! Norm this is working ok for now as is but the next model in my head will fit in a straw, thanks for the tip.

[Norm]

  Zap,

    Yeah that's a lot bigger than I had pictured

in my mind...I'm thinking fine wire springs

like from a wire brush.....

   Micro-Switches!

   Actually you can buy micro switches that will work,

a small metal arm that will be attracted

to the magnet will activate the micro switch...

   I'll bet that as you're

reading this you are holding something

in your hand that has two miro switches !

 Hold the mouse up to your ear and press the

left and right mouse button....( click...click)

   Micro switches !

 You also have two opto-interrupter switches in a

simple mouse with the roller ball...one for

vertical and one for horizontal if you're good

at electronic circuits you could even use these.

....and you can buy a brand new roller ball

mouse at DollarTree for $1 !

 (The switch and arm will fit in a Tic-Tac box)

Tic-Tacs: "You can eat just one...but I would'nt

recommend it."

                   ( :>) Norm

[stevesteve]

Hey Zap, Nice video!

Am I correct in interpreting this as follows:

25. % overlap - starts at slower windspeed
    
50. % overlap - higher final speed of rotation
    
    

Any idea which is actually more efficient at capturing power from the wind?

[zap]

Thanks Steve and your interpretations are correct. Also the 25% will(should have, not tested yet)have better torque.I googled Savonius(wrong spelling in the title)overlap for a few days before I built the 25% overlap and I found there was really nothing concrete as to how overlap was the most efficient, I saw anywhere from zero to 50%. I think it has everything to do with how much wind you have and what you want to do with it. Look here for a good read on testing for pumping water. http://www.iet.co.tz/paper9.htm

I've had a chance to observe the two in some steady low winds and up to maybe 4mph(guessing at wind speed)the 25% overlap makes the 50% look like it's almost standing still. At maybe 2mph the 25% was spinning at maybe 18rpm and the 50% wasn't spinning at all. Again just a guess, but at maybe 6mph the 50% will start to overtake the 25% and by maybe 8mph the 50% will be doing 1.5 times the rpm of the 25%.

I hooked up a spare bike speedo today to the 25% and observed:

9. 5mph for a max speed
   
3. 3mph for an average
   
13. miles distance in about 4 hours.
    
    

If I did my math correctly, 9.5mph is 153rpm.

I try to stay away from saying how easy/difficult something is because of the wide range of experience represented on this forum. Some of the things that Flux, Zubbly, and others find second nature go right over my head, but as theTinker said earlier, this is a pretty simple project.

I don't know about other countries but here in the States plastic buckets are pretty common and can be found at just about any construction site every day being tossed out. Depending on what they contained, they usually clean up easily. A hand saw, sawzall, Dremel, or even a knife could be used to cut them in half.

My plywood was cut with a jig saw to the pattern below but even cutting out rectangles like the dashed line would probably work just about as well.



If you've got a bike sitting around not being used, great! If not, hooking the whole thing to a bearing could be a little work but you could probably even hang it up with string and have it spin well.

[Norm]

  I'm thinking of making my next version similar

to the coffee cans but using four 5 gallon

plastic buckets instead maybe even 6 of them...

 the only way I'll ever get some torque from

these 6 mph winds around here.....without scaring

the neighbors.

              ( :>) Norm.

[hvirtane]

Please see G. Johnson's book about

the wind energy (Introduction)

to get the idea of the performance

of Savonius rotors.

They are in reality much better

than most people are believing.

http://www.eece.ksu.edu/~gjohnson/

- Hannu