There's even a design for a mini single rotor air core axial alternator.
http://www.instructables.com/id/Pringles-Wind-Turbine-Pleech---Version-One/?ALLSTEPS

There is also a more robust version on the same site - Instructables (it's a bit childish, I love it)
http://www.instructables.com/id/Build-a-Savonius-Wind-Turbine-or-VAWT-to-make-elec/?ALLSTEPS

Have fun.

Ben.

Hanging it like that doesn't really work unfortunately. When I hung my pb-vawt from a (crude) u-joint the swinging motion took up a lot of the wind's power and it looked like it was slowing the rotation every time it swung back. It's now got top and bottom bearings and spins much faster/nicer.

I think a good-sized weight at the bottom would help a little if the weight wasn't being spun. You might be able to use a couple of magnets as bearings for that part.

If you plan to trying this out on a larger scale and more permanently then consider the stress on the bearings over time. Maybe bike wheel hubs would last a few years...that's what I'm using on my big one and I'm crossing my fingers.

If you go with gearing I think 1:10 is about right. When I hooked a radiator fan motor to my pb-vawt the ratio was 1:5 and I got a tickle-on-the-tongue for output - not quite the bite of a 9v battery. The vawt was spinning around 36rpm or so, so the motor would've only been spinning around 180rpm...

With a 1:10 ratio, when your vawt hits 100rpm the motor will spin at 1000rpm. That seems decent. If it's smaller and faster then maybe 1:8...I dunno, it's variable and needs to be done on a case-by-case basis, I think.

For a 1 foot diameter rotor the circumference will be 3.14 feet so in a windspeed of 10mph, the outer edge of the rotor will be going 52800 feet/hour or 88 feet/minute.

Dividing the circumferencial speed by the actual circumference gives you 88/3.14=28rpm

I believe optimum loading for a savonius is when it's running at a tsr of 1/3 so to extract maximum power you'd want your alternator to hold it down to a little over 9rpm in a 10mph wind.

You can't really say an s-vawt made from 6" pipe will spin this fast in this wind. Besides the height, you've got weight, air gap, bearings, general build quality, load, etc....lots of things play a part, even with a simple-S design.

Then, are you really talking about a simple Savonius? To me that means each blade is a half circle, the gap is about 18%, the blades don't overlap, there's likely a center rod and you've got end plates. Or are you talking about a modified simple S?..

I consider my quick vawt to be a modified simple S...the blades aren't half circles (though they could be), they do overlap a little, there's no center rod, the gap is totally configurable and a bottom plate is all that's really mandatory (to protect the bottom bearings from the weather).

Past about that point you get into the more complicated designs/problems and all hell breaks loose. Then you start pondering the aspect ratio..wider is better for low winds but is lower rpm, tall and skinny for high winds and high rpms. Oh, should I use those "J" looking blades?..those are more efficient. Etc.