Author Topic: 5 magnet to ten coil ratio  (Read 4538 times)

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JW

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5 magnet to ten coil ratio
« on: September 20, 2007, 12:20:58 AM »
I have have several 2" by 2" magnets. They are the cobalt (high temp) type. I would like to make a wind turbine with a 7' blade dia. Using ten magnets with the dual rotor configuration, five equally spaced with the magnetic circuit closed using dual rotors, and a 5/8 thick stator with 10 coils. I would like to design the stator in 'star' with a total of ten coils, designed to charge a 12volt batt bank. I figure that I could always upgrade the stator for 24volts at a later time. But On the 12volt stator, I am wondering the type of winding to use for each coil in the stator. Such as wire gauge size, and if a multiwire-inhand technegue should be used. Im going to use conventional flooded lead acid type of batterys for the batt bank.


 I will use a five phase rectifier, but am wondering about a realistic amp rating per phase with ten total coils. I plan to wire in star, the more I ponder this I think I should use a ten phase rectifier, with a stator that has eleven(output) leads wired in wye. I do not plan to wire the neutral into anything for generating purposes.


 I have an average wind-speed of 10 to 20 mph, for seven days, with a targeted blade size of 7 foot diameter horizontal wind turbine. I would like to furl at 20 mph.


this project is starting to hit the drawing board, I will update as things progress.


I will call it 'the ten magnet dual rotor too ten coil stator machine'.


 I am open, to an opinion, on reasonable target-max rpm just before furling. This will help me with lathe testing. I may use a self starting circuit to spin up the rotor, from the ground.


 I plan to use aluminum/oxide/saphire powder in the polyester resin, that I will cast the stator with. This is why im interested in testing on the lathe, I would like to determine an operating temp for a properly wired stator, and if possible, increase heat transfer with a sweet-spot rpm using non-submerged magnets on the dual rotors.


JW

« Last Edit: September 20, 2007, 12:20:58 AM by (unknown) »

DanB

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Re: 5 magnet to ten coil ratio
« Reply #1 on: September 19, 2007, 06:38:24 PM »
5 magnets per rotor doesnt make sense to me....  basically you'll have 2 like poles next to each other.  Unless you put all like poles upwards on each rotor - in which case it would be more like a 10 pole machine and it'd be single phase.
« Last Edit: September 19, 2007, 06:38:24 PM by DanB »
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Flux

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Re: 5 magnet to ten coil ratio
« Reply #2 on: September 19, 2007, 11:02:36 PM »
Dan , none of it makes sense to me including cobalt magnets.


Flux

« Last Edit: September 19, 2007, 11:02:36 PM by Flux »

Fiddlehead44

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Re: 5 magnet to ten coil ratio
« Reply #3 on: September 20, 2007, 03:21:37 AM »
COUGH, cough. what you smoking,,,,man??
« Last Edit: September 20, 2007, 03:21:37 AM by Fiddlehead44 »

Raivis

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Re: 5 magnet to ten coil ratio
« Reply #4 on: September 20, 2007, 04:48:03 AM »
Im sorry guys for interrupting your subject, but can you tell me if its worth ordering that book of Forbes called "The homebuilt dynamo"? I kinda red the hvirtane's explanation, but my english is not so good and i'm not a specialist in physics also, so I would need some real pictures to understand. I red an article about this book and it is said there, that book has lots of pictures, I wouldn't hesitate to order this book, but i kind a have financial problems so I'm asking you for your opinion.. ;) So wut ur sayin?


With regards,

Raivis

« Last Edit: September 20, 2007, 04:48:03 AM by Raivis »

Bruce S

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Re: 5 magnet to ten coil ratio
« Reply #5 on: September 20, 2007, 07:31:35 AM »
JW;

  You might want to give a hand drawing of what you're talking about. I can understand the choice of magnets seeing how these can take 300C!! , but unless you have a free supply of the powder, which goes here for $7/oz!! you're going to be getting into some heavy dollars for your 'mill.


I agree with Dan about not being able to understand just how you plan on laying this out.

More details please. Hand-drawn pics work too.


Bruce S

« Last Edit: September 20, 2007, 07:31:35 AM by Bruce S »
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JW

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Re: 5 magnet to ten coil ratio
« Reply #6 on: September 20, 2007, 07:47:15 AM »
I forgot to give the thickness for the SmCo (samarium cobalt sp?)magnets. They are 1/2 thick.


 I am still working on the exact number of coils for the stator, as well as rotor diameter. My design goal is to get the best machine only using 10 magnets. Single rotor may be the answer. But id like to use dual rotors. the magnets are 2inch square and half inch thick. These magnets are just as strong as neo magnets.


JW

« Last Edit: September 20, 2007, 07:47:15 AM by JW »

dinges

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Re: 5 magnet to ten coil ratio
« Reply #7 on: September 20, 2007, 07:59:00 AM »
" Im going to build a dual rotor alt with ten magnets. "


No you are not...


It's very simple; you need an equal amount of N poles and S poles on EACH rotor.


If you build a dual rotor using your 10 magnets, you'd end up with 5 magnets on each plate. 5 is an odd number. 5/2 = 2.5; you'd have to install 2.5 N poles and 2.5 S poles on that rotor...


10 magnets leaves you only with the option of a single rotor axial flux. Reality bites.


The rest of your posting is a bit above my intelligence, so I'll leave that to others to answer.

« Last Edit: September 20, 2007, 07:59:00 AM by dinges »
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dinges

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Re: 5 magnet to ten coil ratio
« Reply #8 on: September 20, 2007, 08:02:52 AM »
I forgot: you could theoratically build a dual rotor axial flux using just 8 magnets.
« Last Edit: September 20, 2007, 08:02:52 AM by dinges »
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Flux

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Re: 5 magnet to ten coil ratio
« Reply #9 on: September 20, 2007, 10:40:35 AM »
Slowly getting there, like getting blood out of a stone sometimes.


Yes Samarium cobalt is fine, costs the earth but if you have them no problem. I assumed you meant cobalt steel ( also good for high temperature) but would need to be 4" thick.


5 poles is a non starter as Peter said, any even number is stupid.


Simplest to use 8 magnets, I haven't checked yet if that would manage 7ft but it might.


If you must use 10 then it has to be 10 pole. Easiest with single rotor but would be possible with dual rotor as the unipolar arrangement that Dan referred to, but spacing would be as 10 pole with half missing. All N on one disc and all S on t'other.


5 coils will only give you single phase, the comments about star and 3 or 5 phase just don't add up.


If you want it 3 phase then pole numbers that are not divisible by 4 will not let you do it as a single layer winding. You can do 10 pole 3 phase with overlapped coils as a 2 layer winding or as a concentric in one layer but you need an odd coil with one long and one short side.


Single rotor is not too bad for overlapped coils as you can bend the ends down over the core. Dual rotor requires you to put the ends in the thickness of the magnets and means that you can't pot the magnets in resin as many do.


Flux

« Last Edit: September 20, 2007, 10:40:35 AM by Flux »

JW

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Re: 5 magnet to ten coil ratio
« Reply #10 on: September 20, 2007, 01:21:58 PM »
    I know this is going to be a challenge. I have the magnets on hand. I honestly think they will be used best on a wind turbine.


 I can reduce the diameter of the blades to less than 7 feet. I just want to construct the best all around alternator that I can, with what I have, as far as magnets go.





I think these are great magnets.





At this point, im leaning towards a single rotor machine. I would like to use all the magnets.


I appreciate the feed back, Im looking forward to completing this, as my first wind turbine. I think its important to note, this turbine will not be raised in a permanet spot. I want to make it sort of portable. I dont think I could manage that, if the blades were bigger than 7' .  Probably not put it up higher than 30 feet.


 Also im considering how make the tower, a concrete footing could be used. But the tower of the turbine itself, would have to be, easily dismantled and easy to put back up.


JW

« Last Edit: September 20, 2007, 01:21:58 PM by JW »

JW

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Re: 5 magnet to ten coil ratio
« Reply #11 on: September 20, 2007, 01:29:40 PM »
"Also im considering how make the tower,"


Arrrgggggggg.


 Also im considering how 'to' make the tower,


JW

« Last Edit: September 20, 2007, 01:29:40 PM by JW »

Flux

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Re: 5 magnet to ten coil ratio
« Reply #12 on: September 20, 2007, 02:06:05 PM »
Not looking good for 7ft with 8 magnets, you would struggle for 250W.


May be a bit better with all 10 and single rotor, the extra magnet rotor diameter would help a lot.


Never had any experience with unipolar machines, the extra diameter would again help but not very good use of the flux with no reversal and an extra mechanical gap to waste winding space compared with the single rotor. Quite a difficult thing to build an overlapped coil winding for a dual rotor to cope with 10 pole 3 phase.


I agree they are nice magnets but you don't have enough of them to build much of a machine. If you want it portable then 6ft may be a better size to aim for.


I will try the figures again for a single rotor but it will take a while doing it the hard way, it's way off anything I have as a starting comparison. Are you seriously worried about loosing performance in low winds with the laminated core?


Possibly another option is a dual rotor with 10 magnets on one disc and none on the other, then you could overhang the end windings over the blank disc but it would need to have a hole in the centre with spokes or something to hold it.


Flux

« Last Edit: September 20, 2007, 02:06:05 PM by Flux »

wooferhound

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Re: 5 magnet to ten coil ratio
« Reply #13 on: September 20, 2007, 02:23:41 PM »
I built a machine with those exact same magnets

But I had 12 magnets which makes for a much better design





http://www.fieldlines.com/story/2004/4/4/164552/3003

« Last Edit: September 20, 2007, 02:23:41 PM by wooferhound »

vawtman

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Re: 5 magnet to ten coil ratio
« Reply #14 on: September 20, 2007, 02:29:40 PM »
I wonder if you could cut them with a wet saw or even a hacksaw?I would think it could be done.Not sure though.
« Last Edit: September 20, 2007, 02:29:40 PM by vawtman »

JW

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Re: 5 magnet to ten coil ratio
« Reply #15 on: September 20, 2007, 03:26:47 PM »
Hi Flux,


"Are you seriously worried about loosing performance in low winds with the laminated core?"


No I am not. This machine faces(will face) the atlantic ocean. There are strong gusts thru-out any given day, even if its not very windy. But on average the wind speed is over 10mph. Since this is sort of designed to be a camping machine :) I will arrive with charged batterys. I figure the usual duration will be 1 month.[we'd go back and forth while leaving the machine and batt bank unattended in that month, for various periods of time] In the winter the winds kick up to 20mph constant on some days. Im much more concerned with 30mph gusts than start up. The only reason I mentioned the self start motor circuit, is because I dont want to climb up the tower.... I figure its going to be pretty lightweight. But the whole rig must be able to withstand 60mph wind gusts. I can use guy wires. I will have to devise a band brake of some sort to lower the tower in bad weather.


 "If you want it portable then 6ft may be a better size to aim for."


I agree. Im wondering if 5 blades could help with this set of parameters. Ither way they would(the blades) be removed for transport.


I really like the idea of overlapping coils with a single rotor. 3 phases would be great to save on rectifier losses. I can see the 3 single phase coil circuits. I hate to ask, but have to, since I cannot see the whole thread while im posting. How many coils for a single phase circuit with ten magnets on a single rotor.


"laminated core"


The only steel I plan on using is the rotor. Are you suggesting that I use iron fillings when I cast the stator, in the center of the coils?


Also, is there anyway a sort of (steel)backing plate can be used inplace of a second rotor. I considered maybe such a thing could work, if atleast, small power magnets were used on sort of a 'dummy' rotor. Do you think that could complete the magnetic circuit?(for the rotor). Still thinking overlapped coils.


Id like to get 800w @15volts dc, in a 25mph wind, with this machine if possible. It would furl after that. If its not possible, id like to do the best I can with a blade dia no smaller than 6ft.


JW  

« Last Edit: September 20, 2007, 03:26:47 PM by JW »

JW

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Re: 5 magnet to ten coil ratio
« Reply #16 on: September 20, 2007, 03:31:11 PM »
Hi Woof,


 Sorry, I was so into my reply to Flux I forgot to post, Im reading about your machine with much interest.


JW

« Last Edit: September 20, 2007, 03:31:11 PM by JW »

TomW

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Re: 5 magnet to ten coil ratio
« Reply #17 on: September 20, 2007, 05:19:10 PM »
JW;



Also, is there anyway a sort of (steel)backing plate can be used inplace of a second rotor.



You sure could use a "passive" second rotor. Basically a dual rotor with one rotor thats just steel. Some folks did that in the past. Can't recall details just that is was done.


Cheers.


TomW

« Last Edit: September 20, 2007, 05:19:10 PM by TomW »
Join in an alternative forum at Anotherpower.com

JW

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Re: 5 magnet to ten coil ratio
« Reply #18 on: September 20, 2007, 05:45:45 PM »
Hi again Woof,


I read the story, and found an additional link/story by you. Personally I think you did a great bitmap image relating to magnetic flux flow during revolution.


http://www.fieldlines.com/story/2003/12/7/225257/916


" The magnets are 2" x 2" x 1/2" Ferrite that I got at a Ham Fest for 50cents each. These are very strong and quite difficult to slide apart when stacked together."


Ya,,,,, These are not the same magnets.


I got my SmCo magnets from wondermagnet, who ever those guys are :). Actually I paid like 20 buck's a-piece for them. There more expensive than neo magnets since they withstand higher temperatures such as 400*f and resist losing magnetic stregth. Neo magnet's start to weaken at 200*f. Actually these same magnets priced out new, on McMaster Carr, cost, 50 bucks per piece. Initally I was going to use these for a MHD experiment. But after I checked the electromagnet that I operate on a regular basis, and noticed that it had like 13,000 guass. Plus its water cooled. But I probably shouldnt throw 13,000 gauss around like that, Im sure when I check it, will be more than 4000 gauss. Theres no way, I designed it that efficient...


"I collected parts for a year before I actually started construction, starting with the Rotors. The first bad idea was to use Cake Pans for the rotors,"


I only see this for one reason. Aluminum(I noticed one was thin gauge steel) will not, complete the magnetic circuit, generated by the magnets themselves. Remember, both rotors are locked in index, while rotating. From the magnets perspective, coils are moving between them, but the magnets (from there perspective) appear not to be in motion.


 Ironically, a steel plate at a thickness of 3/8 inch will not only satisfactory conduct the magnetic field, to the next magnet on the rotor, but also satisfactory support the magnet under opposing loads. Thickness of steel rotor plate will always be related to the magnets field-strength in terms of guass.


"I got concerned about the strength of the cake pans and later poured more Epoxy in there with Wooden ChopStix to stiffen it up some more. Well it was still physically too weak and too much magnetic flux was leaking out of the back, so I cut out 4 sheet metal disks and glued 2 of them to the back of each rotor. It could still use more but it's OK I think."


Woof,


Man, id love to run overthere and check your magnets field-strength with my gaussmeter. I have no way to verify if you actually have the same magnets. Barrium-Ferrite(sp?) is definitly not the same as SmCo.


Im glad you posted. I remember you from way back when, here on the board.


JW

« Last Edit: September 20, 2007, 05:45:45 PM by JW »

JW

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Re: 5 magnet to ten coil ratio
« Reply #19 on: September 20, 2007, 06:53:33 PM »
Tom;


"You sure could use a "passive" second rotor."


   Thanks, my main design objective is the magnets and the 'so-called magnetic-circuit', at least its mainly what ive learned here on fieldlines. It makes sense someone here has done this before. Im going to do my own search with 'dual rotor' as criteria. If I come up with anything, I will post the link to(that) any story relating to a 'passive rotor'.


 Based on what feedback ive gotten, im willing to start winding some coils. Out of the box, im going with 10 coils to the 10 magnet single rotor single phase. Once ive determind a coil shape, I will attempt to overlap 3 phases. Im going to start by cutting out some cardboard peices shaped like the 2in square magnets and determind a diameter for the rotor. I have not figured out how to wire this in delta :)


JW


   

« Last Edit: September 20, 2007, 06:53:33 PM by JW »

JW

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Re: 5 magnet to ten coil ratio
« Reply #20 on: September 20, 2007, 07:22:45 PM »
Damn it again,


"

Possibly another option is a dual rotor with 10 magnets on one disc and none on the other,


Re: 5 magnet to ten coil ratio (3.00 / 0) (#12)

by Flux on Thu Sep 20th, 2007 at 04:06:05 PM MST

"

-

Also, is there anyway a sort of (steel)backing plate can be used inplace of a second rotor.


Re: 5 magnet to ten coil ratio (3.00 / 0) (#16)

by JW on Thu Sep 20th, 2007 at 05:26:47 PM MST

-


You have no idea how many time's, Ive read thru a tread, and seen Flux repeat himself in the exact same words, well atleast twice...


And I just got cought.


  Between Woof's drawing of coil shape for he's machine, and using 10 coils(like DanB said), I could easily overlay 2 additional phases, making a total of 30 coils to ten magnets, using a single rotor with ten magnets. it will be interesting to spin this with and without a passive rotor.


cool stuff.


JW

« Last Edit: September 20, 2007, 07:22:45 PM by JW »

JW

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Re: 5 magnet to ten coil ratio
« Reply #21 on: September 20, 2007, 07:33:31 PM »
The single rotor will have a magnet pole placement of N-S-N-S-N-S-N-S-N-S when viewed top/down in a circular pattern.


JW

« Last Edit: September 20, 2007, 07:33:31 PM by JW »

Flux

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Re: 5 magnet to ten coil ratio
« Reply #22 on: September 20, 2007, 10:51:31 PM »
Single rotor with no return circuit for the flux makes very poor use of the magnets.

I see no point in using it unless you have a source of cheap and convenient magnets, as Hugh does in his 4 ft machine. The common 2 x 1 x 1/2 magnets are probably cheaper than specials even if used inefficiently.


I assumed you were thinking of using a laminated core like the early otherpower machines. Powdered iron in the stator probably would be a bad idea and I doubt that a powdered iron mixture in a separate layer behind the stator would be very effective ( better than nothing)


The spinning steel disc with no magnets is completely effective and is probably your best way to go, it has no disadvantages except that it needs an extra mechanical gap that reduces effective winding space and doesn't cool as well as coils stuck directly on to steel laminates. It also needs half the air gap of a dual rotor, which may make stator manufacture more tricky.


If you are absolutely set on the single phase idea then it will work and may not be too bad in a small machine, you can probably live with the vibration but efficiency will not be so good.


I am not entirely sure what you gain by stacking 3 single phase stators in one air gap, Certainly it will solve the vibration problem but it means a large air gap and low flux.


Somehow if I had to try this route I would use 2 and make it 2 phase.


The concept of a conventional overlapped coil winding is to keep all 3 coil sets in a single plane within the magnetic field so that the gap is the same as single phase. You overlap the coils inside and outside the place swept by the magnets where the excess thickness doesn't matter.


I would wind this thing with 15 coils ( 5 per phase). Each phase would have holes in the coils that accept the 2 coil sides of the other phases. The complete circumference would be wound with no holes. I warn you now that it will be tricky winding to do but not so bad with a thin stator as there is much less mess to cope with in the end windings. As I said previously with a fixed laminated stator the ends can be bent down over the core. You can adopt the same basic approach with the spinning disc but the stator has to be self supporting and the disc needs to be an annulus to accept the inside ends.


You could also wind it as a 2 layer lap winding with the coils overlapped as in a European style 3 phase motor with two coil sides one on the other. makes a nice winding but extremely difficult to do with no slots to position the coils. I have done it twice but don't intend to repeat the process.


One final thought, make it 12 pole single rotor with the spinning flux return disc, 9 coil conventional as everyone else does and just leave out 2 diametrically opposite magnets. Simple and effective, easy to wind but needs a fairly large disc for 12 pole with 2" square magnets.


Flux

« Last Edit: September 20, 2007, 10:51:31 PM by Flux »

Flux

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Re: 5 magnet to ten coil ratio
« Reply #23 on: September 20, 2007, 11:11:49 PM »
That last option was an easy one to check and it would indeed work very well using 10 magnets on a 12 pole machine. Would be somewhat on the powerful side for 7ft if very carefully built. You could more or less throw it together and it should come out ok.


If you can live with at least 16" magnet rotor disc ( preferably 17") then that is by far the easiest way to go. Stator not more than 5/16 thick, 9 coils. Air gap not more than 1/2". Aim to cut in 180 to 200 rpm ( I wouldn't go slower in your wind area).


You need test coils as I really have no idea how SmCo compares with neo.


Ideally 3 blades but if portable then I would seriously consider 2 as it is so much easier to transport. Two blades are a bit rough in yaw but not really an issue at 7ft on a clean wind site. I think I would scale Dan's style blades for 7ft and if you go for 2 blades then increase the blade widths by 50% but keep same angles.


Flux

« Last Edit: September 20, 2007, 11:11:49 PM by Flux »

wooferhound

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Re: 5 magnet to ten coil ratio
« Reply #24 on: September 20, 2007, 11:36:24 PM »
The Cakepans are not Aluminum. They rust and the magnets stick to them very well.


I really don't know what kinda magnets they are. I described them and posted pictures and other people on this forum suggested that they are Ferrite. They are really really strong though. Want to buy a couple of them, I have many more ? Why are you worried about the magnets getting hot, Only the coils get hot.


The magnetic flux diagram you are referring to is not magnetic flux. The redlines you see are the wires in the coils and are represented in two different shapes in order for me to ask my question.


My genny has not flown yet. I plan on putting more steel behind the magnet rotors and get it flying before the end of the year. Yesterday I was trying to get my Solar Electric system installed. 5 Panels totaling 55 watts. I anticipate finishing in the next coupla days, resulting in a new diary entry from me about my new system.


Where are you located, I'm in North Alabama, Huntsville.


Yeah I've been around here since they changed the BBS software to 'Scoop' back in 2003. When I discovered this site I knew that I had found a New Home.


Thanks for the good words . . .

« Last Edit: September 20, 2007, 11:36:24 PM by wooferhound »

wooferhound

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Re: 5 magnet to ten coil ratio
« Reply #25 on: September 20, 2007, 11:52:00 PM »
It's best to build your Magnet rotors first. Then make Test coils and put them in the airgap and spin you magnets up while taking meter readings. Determine which coil is going to work for you, then you can wind the rest of your coils to that spec, Confident that you will get the End results that you want.





Here is a picture of an electric coil winder that I built. Under it is the Jig that I used to hold the test coils in the airgap while I tested them.

« Last Edit: September 20, 2007, 11:52:00 PM by wooferhound »

hiker

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Re: 5 magnet to ten coil ratio
« Reply #26 on: September 21, 2007, 03:25:12 AM »
toss on a bunch of those LOWES  ceramic mags if your going with two rotors..

use the lowes mags on one of them..should be better then no mags at all!!

only a buck 98 for two..well good luck on what ever design you decide upon..

 
« Last Edit: September 21, 2007, 03:25:12 AM by hiker »
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