Felonius Savonius part two

[disaray1]

 Yesterday was interesting for me- I put this contraption

 up, and it works!

  The support is the central tube/driveshaft from a Porsche 944 (a friend owns a porsche repair shop and allows me to scrounge in the scrap pile), the tube is about six feet in length with a bell housing on one end and a square steel flange on the other. Inside the tube is a 24mm (1 inch) torsion driveshaft mounted in 4 very heavy (but very smooth) bearings, drive shaft has splines on each end. I drove the driveshaft half way out of the tube so that only two of the bearings support it. On the square end flange, I made a duplicate flange with a 1 1/8in central hole for the drive shaft to go through. This plate is the thrust bearing support. The thrust bearing is from a 930 turbo. You can see a bike rim mounted to the bottom, and another smaller rim dangling. Those are the belt drive rings, two different sizes for trying a number of drive ratios.

 

 This is the motor (curbside treadmill) I'll try first, driven at 10/1.

 

 With my cordless drill at what I think was about 200rpm, this makes about 19v open, and when connected to a 12volt battery (at 12.4v) made 4+ amps. We'll see what happens. I also have a baldor PM dc 1/2hp I may try also.

 So far, I've got nothing invested in this but my time, but already I've been rewarded with the fact that it spins very well. It rotated all day yesterday, not bad considering there was no wind. An occasional breeze (maybe 5mph) would accelerate it to what I counted (1 mississippi, 2 mississippi) to be 50 to 60 rpm. The neighbor came over to see what I was doing, and watched the thing in amazement. He thought I was powering it with a motor somehow. Nope, just the wind I told him. He says "but there's no wind!" I just looked at him. He came back three times throughout the day and just watched it.

 I need to get an anemometer up and a tach on this thing to get real readings. I also have another drum that goes atop, but have not placed it yet. Thought I would see how one drum does first. Starts by itself just fine, but probably will need some extra torque once the gen is attached. I'm having a great time!

  The first time I ever sailed a Sunfish and it jumped up on plane and started hauling butt was the same rush I got yesterday when it spun to 60rpm. Why didn't someone tell me!?

 Gotta work today, so no play. Update coming when the gen is attached. My immediate goal is 100w...then 500....and then ??

 David

[CmeBREW]

Sounds really good---but I don't see any pictures. Are you sure the pics are less than 100K in size?

[feral air]

You should be able to see them in his files...



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I don't know what the deal really is but I suspect it's the double underscore that keeps them from showing up here. Weird.



Anyway, it looks really good! It'll be interesting to see what it's capable of producing. Interesting color scheme. ;-)

[disaray1]

Lets try this again...

 Another additional thought- only tools used so far: Jig saw, cordless drill, tape measure, string, sandpaper, a C clamp and two wrenches. Oh, and of course a hammer. I welded the drum halves together with the neighbors TIG.

 Windy outside today. Too bad I'm working!

 David

[vawtman]

Hi David

 Hook that motor up to a car battery and see how fast it turns.

 My guesstimate is that it will spin ~500rpms and you would need to better this to charge the battery.

 Try to stay away from gearing if you can.

 Mark

[spinningmagnets]

Thanks disaray1 for the effort, and the pics! One of the things I'm interested in a 3-barrel stacked unit just like this one-barrel (each barrel phased 120 degrees). I fear with the "high torque/low-RPM" that VAWT's are famous for, I may need to add an efficiency-draining gear/belt drive to add some RPM's, but...

I read somewhere that the optimum "overlap" is 18%. Since it looks like you're using the common and affordable 55-gal drum, are you using an 18% overlap? (how many inches does that translate into using a 55-gal?) Thanks in advance! RonR in SoUtah

[feral air]

I'm curious about the gap you chose too since I remember that's what the last post was mostly about.

spinningmagnets, barrels are beastly - big and heavy. If you're really serious about going with 3 barrels then you might want to use plastic barrels instead of steel...and then you're still looking at around 75 pounds in barrel weight alone.

As far as gearing, it may not be needed...

"I maintain that a conversion would be -the- thing for a VAWT. Without the hassle of rewinding you get very low cut-in RPM; for example, the 3hp conversion I've built (absolutely no cog in that) generates .16 V/rpm in star with its original winding; so it would cut-in at 75 RPM. Without gearing. Without cogging. But, it has some iron losses. Then again, it comes in a small waterproof package." -- dinges

I couldn't do a conversion to save my life but...wow...75rpm is low! Even for a vawt that's low.

I wouldn't use barrels though - CmeBREW's squirrel cage vawt is probably the best build/design I've seen. I built a small 2.88sqft squirrel cage vawt today and it seems to work pretty well. I haven't had much time to play with it yet or think about going bigger but..yeah.

...not to hijack the thread or anything, just sayin'....stay away from barrels unless you're getting 'em free and/or like to play.

[disaray1]

Hey Ron- I put up the single barrel so I could get a handle on how it acted and gauge the strength of the support- so far so good, but i do expect a fair bit of flex at the top with two barrels, and three would be insane without a top support.

 I agree about gearing and the losses involved. Some preliminary testing yesterday has me doubting using this type of Savonius at all. At about 80 rpm, 10 to 1 gearing, the small dc motor can drag this machine to 0 rpm in about 5 seconds, and thats just turning the motor unloaded. Two drums would certainly be better. Darrieus would be better still.

 After some more research I find that I may have constructed the barrel incorrectly. The Sandia paper I had been looking at didn't (at least to me) clearly explain gap, hence my first question. I used 4" overlap, which I now believe is wrong. I'm currently researching, so don't listen to anything I say. I used 4" for overlap. 22 inch barrel (standard 55gal), 10% would be 2.2 inches, 20% would be 4.4 inches, so yes, I used about 18%- but- there's a 1" rod going through the middle, and I think that restricts the air flow- more to follow as I get a better understanding of it. This is my first wind powered experience other than sailing.

 Thanks,

 David

[disaray1]

Vman,

 No way to check the rpm on that motor. I'm looking for a handheld tach. I'll strive to get away from the gearing...no time for a motor conversion right now, but that's what it needs, along with more hp. I now see the difficulties involved. Not giving up yet.

 David

[feral air]

Sorry, 2 barrels without a top support is insane too. What do steel barrels weigh, about 50 pounds (I guess it depends on the gauge)? Yikes.

Maybe 18% means each side. If you move the center over 18% from the edge on each barrel half you'd end up with about an 8inch air gap. That's a bit more than I thought but pretty close to the 6 and a half inch gap on my plastic barrel. Like you said, the Sandia paper didn't (at least to me) clearly explain gap.

Now that I think about it though it makes sense....a 22inch barrel is really 44inches once it's cut apart and put in an S shape. Then we can say 4.4inches would be 10% and 8.8inches would be 20%.

Unless I'm totally off my rocker. I dunno.

[spinningmagnets]

I have access to several free 55-gal blue plastic drums. I don't have a specific goal, just having fun and wondering what it'll put out. It's just that 3 barrels is about as big as I figure is manageable for me. I can't have a permanent VAWT, but I can set up a "pop-up" VAWT in the back yard just to get some readings. I also have some long heavy steel pipe available, 1-1/2" to 2" diameter. I plan on using car wheel bearings, one on top, one on bottom, and three guy wires.

I'm thinking I'll start out with a bicycle chain, but if it breaks, I might go to a motorcycle chain. Or, a cars timing toothed belt and gears are very cheap from salvage, has a 2:1 ratio, and with the generator off to the side I can easily swap out several types. I'll probably use a couple 12 VDC truck alternators at first, just because I have them.

I think what you're using is called a "torque tube". There are Ferraris, Porsches, and Corvettes that want to mount the transmission in the back, to make the cars weight more balanced. The torque tube connects the engine block to the trans housing, so the engines torque doesn't twist the body,...sweet find!

[disaray1]

 Yep, it is a torque tube, you nailed it. The 944turboS came with 275hp, I've seen 400+ hp run through these with no problems- that said, the shaft wasn't designed to bend like I'm using it. With the shaft out of the tube, I supported one end with a jack stand, the other end on the ground, and jumped on it in the middle. Spring steel sent me flying like a pogo stick! So it will deflect, and with one barrel the deflection is minimal, but with two, there may be a problem.

 Plastic barrels may be better, but I havent found any yet.

 David

[feral air]

At around 24 pounds a piece I think plastic gives a decent weight savings over steel..less weight means it's more responsive to the wind so, yeah.

With a plastic barrel the outer edges will droop downward is about the only problem I've seen. There's a limit though (obviously) so you can work around it easily enough...hang the rotor for a day in the sun before you do anything you'll regret. If you add some kind of plates/support on the top and bottom that might help keep it from drooping too, I dunno.

Even though they have a weight advantage they're usually really expensive ($60+). Getting 3 for free is down right lucky! I got mine at a local discount hardware store for $30 and I thought that was a good deal. The owner of the store went nuts and bought several semi-truck loads late in '98 figuring there'd be a rush on water barrels before the Y2K bug destroyed civilization...good thing that didn't happen. take it easy