I've been lurking around this site for some time now, and I feel I've learned enough to dive in and attempt my own turbine. I'd like to run my "plans" by the folks here, and get a feel if what I plan to do makes any sense at all, since I'm not too clear on the mathematics of the situation.
Like most people, I'll be trying to blend the conflicting values of doing this on somewhat of a budget, while at the same time getting some reasonable output. I'd like to spend less than $200 on the turbine itself, and I'll deal with all the electronics later. I already have a 12V bank and inverter, so that seems to have me set on 12V at this point.
It will be the classic dual rotor axial flux air core deal, since that design seems to be well-studied around these parts, so everyone should be able to give me a great deal of help.
I'll start with a front-end wheel bearing and brake rotors from a Plymouth Reliant. We have had a dozen K-Cars at our house over the years, so these parts are 100% free. The brake rotors are a bit small, about 9.5 inches in diameter, but I also only plan on using 1" magnets, so it should be all good. Precisely I plan to use 12 of the 1" diameter by 1/4" disc neo (product #1) on each rotor.
I'd like to build a 12V unit, so this is where I need the real help. All of the designs on the Otherpower site are using the giant 2" x 1/2" magnets. That's nowhere near my price range, nor my desire for safety. So, with 1" x 1/4" magnets, how many turns do I put in my coils to get my 12V?
Do I have to increase the number of turns to compensate for the weaker magnetic field, or is that how it works at all?
If so, I can make some assumptions... The strength of magnets seems to be roughly analogous to the raw volume of magnetic metal, so can I assume that since the 1" magnets have about 1/10 the volume of the 2" ones, that I will need 10 times the number of turns in my coil to get the same voltage? That doesn't sound right to me at all... Since most of the 12V rotors using 2" magnets are using around 30 turns, that would give me some 300 turns. I'm going to guess that's wrong thinking, since that much wire at the gauge required to fit in a 1/4" stator would have significant resistance at 12V. So, I need some help here.
I'm thinking of building an 8' diameter blade, but I'm also thinking this might be too big. Here's another area where I need some guidance. I decided on 8' mostly because if I go and buy a board it will be 8 feet long. I've not seen a website that says "I wish we'd made the blades smaller" so I assume that making them slightly too large is not a big issue.
A lot of variables, that's for sure. I know the best way to get this right is to build the magnet rotors and build a test coil, so the best suggestion I could receive right now is what gauge of wire to buy. If my number of turns will have to be large, I guess I'll be around 16 gauge. Otherwise, I'd go with 14, and I can double/triple it up if I want fewer turns than that, since it seems the popular preference is for winding with 14 gauge wire.
Umm... yeah... I'm long winded. So... advice, then?