Finding the right generator

[khabe]

For a small wind genny you could use a brushless outrunner motor.

They are small motors for model cars and planes that have moving neo mags and stationary coils. They are VERY efficient motors and make quite efficient gennys.

They come in all sorts of sizes from tiny to large so you should find one to match your turbine. They are also quite cheap on ebay:

http://shop.ebay.com/?&_nkw=brushless+outrunner

They will generate 3 phase AC when cranked. With three bridge rectifiers feeding a cap you get rough DC, can then use efficient regulator for proper DC.

Yes, but even low cogging outerrunner brushless RC motors  (12 tooth/10 or 14 pole and 9/8 ... 9/10 ... 18/16 ... 18/20 ...)  have cogging too much for small windmill - it will not self-start. And those motors are cheap but not very cheap ---. $30 for tiny ones and up to $300 for larges. Tiny ones has tiny bearings and thin shaft as well. At that kV of these motors is at 500 to 3500.  When kV is 1000 then you need 1000 rpm for get one Volt !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! And this is NO LOAD VOLT !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!     
regards,
khabe

[Yucca]

Yes, but even low cogging outerrunner brushless RC motors  (12 tooth/10 or 14 pole and 9/8 ... 9/10 ... 18/16 ... 18/20 ...)  have cogging too much for small windmill - it will not self-start. And those motors are cheap but not very cheap ---. $30 for tiny ones and up to $300 for larges. Tiny ones has tiny bearings and thin shaft as well. At that kV of these motors is at 500 to 3500.  When kV is 1000 then you need 1000 rpm for get one Volt !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
regards,
khabe

I have a small outrunner from Hong Kong about $15 on ebay and yes I notice it has noticable no load cogging even though it has different number of poles to mags? I think a wind turbine of a couple feet diam would start one running though.

You´re right the kV on the normal model motors is too high for direct to turbine and cogging will amplify through gearing.

I suppose a rewind with finer wire for lower kV would help but then that´s a fiddly long winded job.

Yucca.

[khabe]

My bread-and-butter comes from generators Im developing and building past 10 years, even longer,
Those are very specifics, but el.machines anyway, at that sui generis and ... devilishly good (they are speaking, the customers
As more specific - as higher price
regards,
khabe

[TinselKoala]

I guess I paid about 2 dollars for this little motor that makes a pretty good demonstrator generator.
We're not trying to save the world from the tyranny of oil, here, we're just trying to help a kid do a science fair project, and I have a hunch he's not (yet) attending MIT, so it doesn't have to be too complicated.
Neither does it have to be the most efficient generator, or the fanciest technology.
A mechanically commutated DC motor won't require rectification, and if the right type of motor is chosen it won't exhibit "cogging" or excessive bearing drag, and so will be easy to turn with a wind turbine or water wheel or even a hamster in a cage, without complicated transmissions or gearing.
And a demonstration using this kind of motor will give the presenter ample opportunity to discuss issues of overall efficiency, ease of construction and maintenance, environmental impact, not to mention the physics of electromagnetism.
http://www.youtube.com/watch?v=kFavcqNWF5I

[Thaelin]

   Very simple setup would be to take the 12 mag 9 coil and make it smaller. Use grade 8 magnets from the hardware shop and smaller wire. Since its a concept show and not a off the grid system, many options. Not to mention he will learn the ins and outs of construction.

   And now, Uber thanks to all here that have posted as you have given me the final piece to my long sought puzzle of the coil make up. I have yet to find out the turns or ohm rateing  for a standard system. All I could find was let us sell you a kit or a video of how they made them but no specs. So now I build. I have to have 12v @ 25A output at a fairly low speed and this will do it. Less than 300rpm.

thaelin