Need help for small low cost genny.

[Jimmer]

I'm a newby and would like to build a small windmill for our country place, to keep some batteries charged.  I don't have a lot of money and need to use what I have.  I can scrounge up the wood and other metal required for the tower and other uses.  How many watts could I produce with 8 - 1" X .5" neos and 16 AWG wire.  Could I produce 40-50 Watts with them?  How many number of turns would be needed for each coil and how many coils of the 16AWG wire?  What size prop would be required?    Thanks for your help?  Jim

[Flux]

should be possible, I take it you have 8 magnets 1" dia and 1/2" thick.

Stuck with #16 wire is a limitation but you can do it.

Try your magnets on a disc about 7.5" diameter or use the common 8" disc and keep them in from the edge a bit.

Use another blank rotating disc as in a dual rotor but with no magnets.

Make the coils with a 1" hole and keep them to 3/8" thick.

You should get 80 turns per coil and still fit 6 coils in the diameter of the magnets. You may get a few more turns if you are careful.If they will not fit, try squashing them to an oval shape until they do.

You may have an issue with the hub unless you can find something small as there will not be a very big hole in the stator.

Connect as star with 2 coils in series per phase.

You will need a prop with tsr of 6 or 7 and about 4 ft diameter. On peaks it ought to do about 150W.

Much depends on the grade of neo you have, I assumed N35 but with better grades you may manage a larger prop with improvement in low wind.

Flux

[Slingshot]

Flux,

What is the thought process to decide on all 8 magnets on one rotor (with rotating blank second disk), versus 4 per disk ("standard" dual rotor) and three coils?  Not challenging the result, just wondering what the important tradeoffs were.

[Flux]

4 of those little magnets would need such a small disc that there would be little room for windings and even with 8 there is an issue with size of hub, it just wouldn't go with 4 .

Also it pays to keep the frequency up, that is one factor in the emf equation. If you can gain more with frequency than you loose in flux then you come off better.

In this case the magnets are reasonably long ang you can still manage a useful coil thickness with one magnet and a return path. This is not a general case and it wouldn't normally make sense to change a 12 pole dual rotor to 24 pole with return disc.

It takes a fair bit of instinct to know which way to go.

Flux

[wooferhound]

A zillian years ago in Physics class I remember learning that,

Everytime that you Double the Frequency, you Double the Energy.

[vawtman]

Have you thought about a small motor conversion or a dc motor.That would be the cheapest route I think and most of the work is already done at the factory.Have fun.

[Jimmer]

I have been thinking about this too, just which motor for a reasonable price?  

Jim

[Jimmer]

No, I don't have the magnets, just know a place I can get them(N38) at a decent price and what I can afford(maybe even 16).  The wire I have.

You mentioned the coild should be kept to 3/8" thick is that out from the center or the thickness from the plate?

How do I build blade with a TSR of 6 or 7?  What about a 6ft blade or even 8ft?  You mentioned that a larger prop will improve in low wind?

Thanks for the inputs, I really enjoy this site, I just need to start building.  

Thanks Again, Jim