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The learning curve.

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ksouers:
Well, it’s been an interesting couple of weeks. I don’t yet have all the parts I need build my first alternator but I thought I should at least get some experience building a turbine. To that end I dug around in one of the many junk drawers and pulled out a couple motors I managed to liberate from an ink jet printer picked up at a garage sale a couple years ago.

Spinning this motor in the lathe only gets 7-8 volts at 2000 rpm. I know, that’s “not useful” for anything. Except yes, it is useful for learning, as long that knowledge doesn’t require a specific voltage. Then whatever voltage you get simply becomes a reference, a metric, if you will.

In this instance the fundamentals of turbine operations and design is the knowledge sought. The mechanics of how things work, and what doesn’t, is what I need. Sorry, I didn’t get any pictures. At least not yet, the learning is still ongoing. The first iterations have been quite ugly. Extremely so.

I used structural foam for the blades. You know, the pink stuff you get at Home Despot and such. I used the most basic airfoil I know, the Kline-Fogelmann. It’s used extensively in scratch built model RC planes, as is the foam. The airfoil has nice low speed characteristics making it great for the foam airplanes. It’s also very easy to make, since it is basically a slab with a step in it, make your base from one piece of foam then hot glue another piece on top that has about 2/3 less chord. Shape it a bit and you’re done. I can make a set of blade in about 15 minutes like this.

So, what exactly did I learn? Lot’s of stuff. Nothing empirical but, then, it was subjective data that I was after anyway.

1)   Twist is very important. I knew that from the beginning but had to start out with straight slab blades to find out just how important it is. Do not underestimate it.
2)   Mass always wins. One of my own sayings I’ve used for years. It stays true even with wind turbines. The light foam blades start and stop quickly. Mass needs to be added to perform smoothly.
3)   Match the blades to the generator. Yeah, I learned that from you guys. I made long and short blades. Short worked best with the small motor.
4)   Someone else said it best: “The wind doesn’t blow here, it sucks!” Sorry, I don’t remember who. But it’s very true. I knew this was a lousy wind site. I just didn’t know how bad. I do now. Because of all the buildings and trees there is much turbulence and wind changes direction constantly. The turbine will blast alone for a second or two putting out a couple volts then abruptly stop. Or it may swing wildly, usually within about 120 degree arc but I’ve seen 180 degrees or more frequently. Usually it seems like its doing a three at once.

The education will continue. I have lot's of things I want to try, and to learn.

Kevin

ghurd:
Big fun in little packages!
G-
(Woof said your quote)

JeffD:
Yes, the never ending learning curve, but it is fun, most of the time.

Glad to see some one else trying the KF airfoil.  I started experimenting with it in October 2009 and in Jan 2010 changed all of my little turbines to using the KFM3.

ksouers:
ghurd: Yes, it is. Thanks for attributing the quote. Sorry Woof.

Jeff: I've been using the KFM2, I may try the KFM3. The blades could use the extra stiffness, I've had several tower strikes with the gusty winds we have here bending the blades back. What did you use to make the KFM3 blades?

ghurd:
If you want something "useful", try a stepper motor (also from printers).
Can charge AA ni-cads/Ni-Mhs, and everybody needs their AAs recharged.
I had some nice pics from a couple people of such projects.  Lost with a 'puter crash.

Yards with trees and buildings, and a 6' tower, usually have somewhere the wind is less turbulent.
Mine has 3 places.  Can't see the best place from inside the house, so I can't leave one there.
The other 2 places have a wind tunnel effect due to the wind being guided between houses and trees.

Turbulence will cause the blades to very quickly nearly stop, even with wood blades.  I don't think heavier blades will help a lot.

Did you see my ruler blades?
I think I will call them "GHm1".  LOL
http://www.otherpower.com/toymill.html#glenh

G-

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