What size coils for 1.625 dia x 1.1 neos

[Blastoff]

I'm guessing a 5/8" thick stator?  The rotor will be 1/2" steel, Once the coils are designed, I think they will determine the diameter, right?  I've been lurking and reading for some time and I love the board.  I'd like to get as much as I can out of her, so I'm trying to do my homework first.  After reading about the 17ft machine on the Otherpower site I really got excited.  I figure to scale down from that a little.  Can anyone help me with the coils, like wire size, turns and thickness.

This is the perfect winter project!!!

Thanks,

Dave... aka Blastoff

[Shadow]

Hi, I'm not sure your magnet size, Is that inches?..Millimeters? Anyway mine is a dual rotor, 12/9 configuration 48 volt. I used 2x1x1/2 inch Neos, 1/2 inch thick stator, 3/8 inch steel discs 11 1/4 inch diameter.140 turns per coil of#17 magnet wire. Cut in speed in about 152 rpm.70 inch cedar blades for a swept area of just under 12 feet.I have seen 1800 watts at furling from this machine.I hope this helps you, its a start anyway. Good Luck

[Blastoff]

My neo magnetics are 1.625" dia x 1.1"thick.  I think the blade dia. will be 10 - 12 ft dia.  Your turbine sounds great.  Since my magnetics are a little bigger might I get a little more out of her?  Is 5/8" stator to wide?

Thanks again for all the help,

Dave

[dinges]

The only way to be sure about the right 'size' (what is size? length, depth, width? number of turns? thickness of coils? wire size? one wire or multiple wires/coil? square or round wire? etc.etc.)

Wind one test coil, put it between the stators, and see how much voltage you get at what RPM. Then decide how much room you need for each coil; account for the wire diameter; is there enough room on your stator for these coils? Will you get enough voltage at your intended minimum RPM? Will output be limited by internal resistance? If so, will you get more output with a bit thicker wire and less turns, even though voltage will be lower? etc.etc.

I scribbled a few pages full of quick calc's to get to an 'optimum' situation (which probably isn't the real optimum).

If you want to avoid this difficult path, stick to a proven design and simply copy. If you like design challenges (like me) and don't mind winding a new stator because the first one doesn't work out, despite the fact that your calc's say it should work (this of course never happened to me!), go ahead and design your own.

The fact that you ask the question implies that you don't have the knowledge (yet) to design your own. Nothing that can't be cured with a bit of study though. Reading of other people's mistakes (like my coils having to small internal holes) can prevent a lot of extra work.

You decide.

Peter,

The Netherlands.

[dinges]

BTW, whether this is the perfect winterproject depends upon where you do your construction; if it's in an unheated shed, like mine, it'll more be a summertime project :-) No wait, too hot in summer; a spring-and-autumn project?

Peter,

The Netherlands.

[willib]

where did you find those magnets? email me if ya want to.

the optimum size coil for round magnets is twice the magnet dia.so your coils will be 3.25" dia. with a hole the size of your magnet dia..

For a 9 coil 12 magnet machine you need 11.169" dia rotors, with coils spaced evenly every 40 degrees , and magnets spaced evenly every 30 degrees.

5/8 " coils are not too big for the size magnets you are using , but you may not need to go that thick ,after you build your rotors make a test coil as peter suggested i would suggest using something thicker than 17 ga. to keep the resistance of the coils as low as possible..

[Flux]

5/8 stator is thin for those magnets. For dual rotor I would go over 1". Use larger discs to reduce leakage between magnets.

I don't think I would do it that way at all if I wanted the most from those magnets.

I would use a single rotor with 24 magnets, stator about 5/8 to 3/4 thick and use a steel plate with no magnets for the return path ( spinning as in a normal dual rotor).

Flux

[Blastoff]

Willibur,

Thanks for the info.  I worked out about the same lay out on emachine.  I will make a test coil once I come up with the rotor lay out.  I glad you said I could possibly go thicker than 5/8".  The more I preplan the less problems I hope to encounter.  Should my dia. be larger than 12" due to the leakage Flux talked about?

Flux,

I hadn't even considered a single magnetic plane with an addition steel plate for a return path (interesting)!!  I also didn't think about leakage on a 12" dia. rotor.  How far apart do you suggest keeping these magnetics?  My head is swimming!!

I guess my first job after all the planning is to build the base machine, which includes the rotors, so to build the rotors I need to plan the stator, which I can't build until I test the coil, which I can't test until I build the base machine, which.... aaaaaaaaaaa... overload... drink beer... better now...

Any help is greatful, I was reading last night till 2am... so much info

Thanks again,

Dave

[willib]

you can go bigger than 11.169 " dia rotors , BUT why ? if you dont have to..

with dual rotors there will be no leakage to speak of , as the magnets are ROUND.

so build your rotors ,and use allthread between the rotors , and leave enough so you can vary the width to the size of the stator that you will end up with..

no need to commit yourself by putting resin on the rotors !! the ones i am using now are just stuck to the rotors , no resin..

[dinges]

I clamp mine in place with superglue, but haven't used epoxy yet. The magnetic force is big enough to keep them in place (in my designs so far), the CA glue provides some extra security. Still possible to release them, if necessary (CA is brittle).

However, my first real windgenerator will be cast in polyester (the rotors that is). For reliability and weather & mechanical protection of the magnets. Though I think the CA-glue would do the job. Why risk it by skimping on a bit of cheap polyester resin? The extra work is negligeable (?) too.

For testing purposes though, I wouldn't think twice about just clamping the magnets in place, without glue or epoxy. However, you think you can get your magnets loose again, even without the glue/epoxy? I think I wouldn't want to try it with your 1.63"*1.1" magnets...

Peter,

The Netherlands.

[Blastoff]

Excellent ideas about the rotors (thanks a million)!  I can't wait to get started.  I have the steel plate and spindle coming in a few days and the mig is waiting.  I'll post pics once done.

Back to the coils... For a 48 volt 9 coil 3 phase system, how many turns should I start with?  I think this will determine the size wire I order.  Is #16 wire about the right size to start with?

Does super glue attack the mag. wire coating at all?

Thanks,

Dave

Erie, PA (avg wind ~12mph on the hill)  

[dinges]

attack not; attach yes.

About the nr. of turns/coil for 48V; either wind a test coil before committing to an entire stator; or, if you have a design that you are simply copying, but is 24V, just double number of turns, and calculate or wind a test coil to see what is the thickest wire size that still fits in the physical space.

BTW, if you are in doubt about your own wire/glue, just try it out on a piece of wire; quick & easy.

The MIG is waiting eh? For years I was planning to learn how to TIG; now I have a real need for RE applications, I will learn ASAP. Coming saturday I'll get my TIG torches; next to find a supply of gas, and then I'll start to practice,practice,practice. Welding aluminium would be really nice too...

Peter,

The Netherlands.

[willib]

where did you order your rotors from ? emachineshop?

i've designed my new rotors but havnt ordered them yet ..





they are quite big , 21 inches in dia.

[dinges]

Willib,

You've just given me a good idea. I had played with the idea before, but never 'visualized' it like this! One picture & a  1000 words...

Major benefit might be better cooling of the stator too, besides weight reduction. Plus, it looks good.

Look at what you've done, now I've got to make new CAD-drawings for my 10ft genny ;-)

And if you use a ring for the back-side rotor (furthest from the prop).... The extra increase in rotor-diameter might be more than offset by weight savings.

Peter,

The Netherlands.

[Blastoff]

Willib,

Nice picture and a cool idea. 1/2 thick?  I only was designing mine on Emachine, I think I'll cut my own or have them done locally, if I find a good price.  Do you think the cut outs would effect the flux flow?

Let us know if the Emachine plates come out, if you order them.  Does anyone know how good Emachine is?  Is the cost worth it?  It really seems so simple to design using there software!!

[dinges]

Yes, you hit the hammer on the nail; which comes first, the chicken or the egg.

Basically in my case it was trial & error on paper & cad-screen; draw a sketch of rotor; enough room for coils (but what size is a coil?)? But how many windings do I need, and what diameter, and... Redraw rotor with different size;

Anyway in the end I needed double the amount of turns/coil (130 instead of 70) with my too small NdFeB-magnets with too large air-gap; this meant using thinner wire, higher internal resistance, more losses in the stator, etc. But the thing is expected to only generate about 10W (.8m dia prop), 50-60W absolute maximum. It'll be used on the boat anyway. (Actually, I'm thinking about building a PMG to couple to the propellor-axle of the boat; when sailing, the propellor freewheels; it should be possible to extract some energy from it, even despite the low (100RPM?) RPMs of the prop). I have seen outboard generators like this before, so the idea has been tried before.

A windgenny is basically one big compromise, like any engineering project. I liked designing my own, even though I had never built a genny according to someone else's plans; forced me to do a lot of reading & learning in a short time. Made the odd error or two, but my genny still works (though it could have been better).

My advice: consider your first genny a learning experience, from which you will learn from the mistakes you make. (even my 2nd one was a learning experience). Now with the 3d one, I feel I'm ready for the real works. But the first two have been great fun building!

Remember: 'things become important to you not because of what they are, but because of the time and effort you invested in them' (Saint-Exupéry)

Peter,

The Netherlands.

[dinges]

Yes, it may SEEM easy :-)

Just as I found out recently that when I draw a hole in AutoCAD of 3.0 mm, it comes out of the machine shop (lasercut) exactly as 3.0mm; which means my bolts didn't fit, and I had to drill out the holes with 3.1 mm ; I had a good pilot hole though :-)

Or that when you draw a square, it comes out square, with VERY sharp corners. It only takes one extra command in ACAD (fillet or chamfer), or some minutes of filing by hand. Another lesson learned. This is the kind of things they didn't teach in school...

Peter,

The Netherlands.