A small, inexpensive first windmill project?

[esc]

After making significant progress on my trailer mounted tower yesterday, I started thinking about what my next project should be.

Having never built a windmill myself I figure I should start with something small.  Also easy and inexpensive would be good.  What I am after here (for now) is little more than a science experiment.  In the end, all I'm really looking to do is power a light bulb.  With what I have been reading here lately I have a few ideas I would like to throw up in the air and see where they land.

Small, cheap and easy makes me think of PVC blades. So...  

Using a 6" diameter pipe, how big (diameter) of a 1 piece blade set can I make?  

How much power could I expect to generate (assuming mediocre efficiencies for all components) and light/medium winds?

Next I will need an alternator.  No point fighting the wind around here so it might as well be an axial flux unit.  So how do I make one that is small and cheap?

I would like to use inexpensive, off the shelf components that I can acquire locally.  

Harbor Freight is having a sale on their 1 7/8" x 7/8" x 3/8" 5lb pull ceramic magnets.  They are only $0.50 each ($1.00 for 2) this weekend.  

Then I could go to radio shack and get some wire like this:

    * 40 feet of 22-gauge wire

    * 75 feet of 26-gauge wire

    * 200 feet of 30-gauge wire

http://www.radioshack.com/product/index.jsp?productId=2036277

Would it be too small for what I want to do?  I suppose it depends on how much power we are talking about.  How much power would an alternator made of this wire be able to make without burning up?  Considering the thin wire I'm thinking that I should go for as high a voltage as I can manage.  Thoughts?

Would it be possible to make a mini-axial flux alternator out of this stuff?  Probably.  Would it be worth the time and effort?  I don't know.  I suppose, as a training exercise it has some merit, but if I can not expect to generate a reasonable amount of power I won't bother.  How do I define a reasonable amount of power? Something that will be reasonably well matched to the PVC blades.

So figuring out if it would be possible to build a useful alternator out of these inexpensive components may involve some complex computations (I know that I don't know how to do it...yet), so if it too much to ask, just let me know.

Also, if I missed any relevant stories on this board or else where please point me in their direction.

Thanks,

Eric

[wooferhound]

I always thought that Ghurd's box fan conversion would be a good place to start

http://www.fieldlines.com/story/2005/7/4/34446/17324

but try to use something better than ceramic magnets or you will be scared away from wind power too soon.

As for the PVC blades made from 6 inch pipe, I would'nt go any longer than about 7 feet. If you get any wind at all they will bend back and break when they hit the tower mast. Also with PVC props it is hard to get really good fast RPMs so you should be thinking of some fairly short PVC blades so the RPM will be higher.

[spinningmagnets]

If you just want a tiny wind-gen to show the kids, I "think" someone said a while back that the motor in a copier/scanner uses permanent magnets. If this is true, you might be able to easily make a wind-gen from it. It wouldn't take much to inspire your kids!

I seem to remember that LED lights are very easy to get lit up with a tiny amount of power. Perhaps if such a tiny turbine can put out 2 volts, you could even make a 1.5-volt battery charger? My memory isn't so good anymore, but I hope I have at least given you some useful search terms. Best of luck!

[esc]

Ghurd's box fan is interesting, but I would prefer to make my own "mini" axial flux alternator.  I like the 4 magnet 6 coil idea.  If I use ceramic magnets maybe it had better be a 40 magnet to 6 coil design?  (Just kidding)

I hear what you are saying about the ceramic magnets.  I'll guess I'll price a few neos, but I really wanted to be able to get everything locally.

OK, 7 feet is MUCH bigger than I had anticipated.  I was thinking something more like 4 or 5 feet.  Could I make a sturdy set at was about 5'?  How about 6'? What kind of RPM am I likely to see in a 15 mph wind?  For that matter, assuming a 5' blade of average quality and a 15 mph wind, how many watts might we be talking about?  I just trying get

bearings and a sense of scale for what I am talking about.

Don't worry, if you give me an estimate and my project comes out with power production of 1% of your estimate I won't blame you.  

Now that I think about it, if we are talking about a 5' or 6' diameter blade, "MINI" is probably not the best description of the size alternator I will need.  Maybe I should scale up my project design a little.

[esc]

Thank you for the suggestion, but what I am really after is practice.  I want to build a small axial flux generator so that I can get to know the process.

[hiker]

heres a simple little dual rotor alt...7 1/4" sawblade rotors..

ceramic and neo mags..

main mount is made from 2by4s--shelf hangers for stator mount..

couple of block bearings-- plywood stator with cutouts for coils real simple but strong..   wire  size maybe #222

alt is a 6and8 setup JERRY rigged...........

[ghurd]

Cheap and Small are my favorite things.

Forget the RatShak wire.  Find an old TV and remove the degaussing coil.  100's of feet of nice clean wire about #20 or #21.  Just unwrap the black tape, and it is ready to use.

I got a $5 wheel from Harbor Freight for like $2 with a coupon.  HF item #30900.  It may be a nice place to start with small and cheap.

It has bearings for a 5/8" axle, and the hub comes off the rim with 4 bolts, leaving the 2 bearings and a nice flat place to mount things to. ~2.75" bolt pattern.

The bearings are not too bad!  Better than the $10 each bearings at the local hardware store.  I doubt they'll last a year in a good wind location.

The plan is a single rotor, no laminations (laminations pull against the bearings with a lot of force), maybe 8 magnet and 12 overlapping coils, Jerry Rigged, maybe 3' dia.  

Not a great design, but thats still the plan.

Oversized 60K wheel hub pic...

http://www.otherpower.com/images/scimages/2050/PDR_0001.JPG

Best to start with neos.  I wouldn't bother with ceramics on a first project.

It's only cheaper until you have to replace the ceramics with neos so it works.

Neos need a lot less turns of wire, meaning less resistance and more output.

G-

[wooferhound]

You can get a lot of neo magnets cheap here

http://dealextreme.com/products.dx/category.1105

you would need to stack them to make it work good

free shipping too . . .

[esc]

Hiker,

I like the wood alternator. That is about the scale I was thinking.  I have scrap metal and a welder so I will probably use that, not wood, for most of it.  But I may use wood for the stator.  What kind of power does it make and what size blades are you using on it?

Wooferhound,

Thanks, but I think that trying to piece together a bunch of small magnets, to save a few bucks, gets on the wrong side of my cost/benefit tolerance.

Ghurd,

I have a bunch of 5/8 bearings and steel rods in my scrap pile that I can probably use.  I can also get good sealed bearings for a buck or two at a local bearing house.

I also would like to make a 2 rotor generator.

Thank you all for  your suggestions.  I'm going to mull them over for a while and go stare at my scrap pile and see what I can think of.  Then I be back with an updated plan.

[spinningmagnets]

That's actually a great idea esc, no matter how much I read about a new thing, there's always something extra you learn when getting your fingernails dirty!

[Jerry]

Hi esc.

I built my first dual rotor in 2005. I used the HF ceramics. I actuly got mine at Lowes, same magnet though.

I had the same idea. I didn't want to use expencive parts on my first dual rotor build and conciderd it to be a training exerzise.

I built the normal 12 magnet per disc and 9 coils with one big eception. I used 24 ga. wire.

The small wire worked very well because of 1 very important fact. I wound each coil with 350 turns. Then the biggy, I used a small 6 amp fullwave bridge rectifier on each coil.

Its called "Jerry Rigged" as mentioned by the guys above. 24 ga. sounds very small but when "Jerry Rigged" with 9 coils esentualy wired in perelell its equal to about 14.5 ga. wire.

24 ga. is 404 circular mills X 9 = 3636 circular mills. 14 ga. is 4107 circular mills, 15 ga. is 3257 circular mills.

I salvaged the fullwave bridge rectifiers from old garbage disposal motors from dumpster diving( free is a very good price). These must be the dc pm type motors. About 1/4 of all garbage disposals use these.

Hiker inspiered me to use old saw blades, never again. They were way to hard to machine.

Use some old brake discs they are typicaly free also. I made mine 10"

I used my 4ft "Jerry Blades". PVC blades will work very well.

A pipe blade that has been way over looked here is the PVC foam filled pipe. Its about 5/16" thick and very riged. I have pictures.

Speaking of pictures, I was just looking at my 2005 diary on this genny and most of the pictures in that story are gone but here is the story. This may take a long time to load. I made my picture files to large then and that may be why so many pictures are missing.

      http://www.fieldlines.com/story/2005/1/30/4118/94606

I'm curently building aa new dual disc alt with 14 ceramic HF magets per disc and 11 coils and yes "Jerry Rigged".

The power #s are in that diary.

                          JK TAS Jerry

[Jerry]

Here is the 4ft foam center filed pipe blade with wood hub and Lowes $8 nose cone.

Nose cone is not nessesarey its just for looks.

A plumber freind had a 3ft scrap of this 6" diameter pipe. It makes a very nice and strong blade. A thin pice of plastic is laminated to each side of the foam. Verry rigged and light. I cut it into 4 sections. So I took the best 3 out of 4  2ft blades and then made the plywood hub.

There is a story with pictures on this one also.

Just look at all 400 pictures in my files you might see a good idea or 2.

                           JK TAS Jerry

[Jerry]

Here are a few more pictures for motor conversions I've done.

These are Lowes ceramics, No cogging but very low output.

Here is a new rotor I built for my 2 faced GM alt conversion. Cogs real bad

Here are some scewed #29s for my Garbogen that doesn't cog much with straight magnets. I saw a 10% decrease in power with these.

Here is the solid steel armature I use on the Garbogen.

Here is the rotor with magnets. The end cap magnet retainers are aluminum and the centering screws a SS so no flux path or lose here.

               JK TAS Jerry

[esc]

Jerry,

That is a very interesting build.  Very much in line with what I have in mind.  But it raises a bunch of questions...

You got 60 watts in a 15 mph wind with the ceramic magnets?  Any estimate as to what it would make with the neos?  What if the ceramics were doubled up?

What kind of blades are those?

It put out 12v at all speeds?  Why is that?  It seems a little odd to me.

Why did you used several stacked saw blades for each rotor?

Thanks,

Eric

[esc]

I have another question or two...

It seems like using old disk brakes for the rotors would add a lot of unnecessary weight.  Does the extra iron have some benefit magnetically?

I'm also wondering about rotational mass.  I'm just thinking out loud right now...It seems to me that the less rotational mass, the easier it will be to get the thing to turn in light winds.  A smaller diameter alternator would tend to be easier to get turning...but that would also slow down the speed at which the magnets are traveling.  It also reduces the room available for coils and magnets.

So what would happen if you took all the coils and magnets from a larger design, and placed them in a smaller diameter, 3 rotor, 2 stator sandwich?  I think that having the mass closer to the axis would make it easier to turn.  It would also mean that the blades could apply more torque at any given wind speed, reducing stall.   If you wanted to scale it up you could add more layers as needed, reusing the same standard parts.

I'm also wondering about the coil vs magnet ratio.  As I understand it, the main goal is to have a multiple of 3 coils to provide 3 phase (assuming you want 3 phase), while having a number of magnets that will line up with only one phase at a time, but will line up with all coils of that phase at once.  Is that right?

[Jerry]

Hi esc.

Sorry about the motor conversion pictures. It was late tast night and those picture were ment for a motor conversion story with cogging isues not this thred.

Sorry I goofed?

I'll try to answer your other question later.

                          JK TAS Jerry

[hamitduk]

The wire is non insulated, I think the number of wraps will all ways be one?

[esc]

I've been researching some of my own questions and think I have partial answers now.

As far as "the extra iron" in a disk brake, I see now that it is important to have enough to "capture" the magnetic field and channel it back in to the adjacent magnets.  So how do you know how much is enough?  

What if a compass were positioned near the disk, on the opposite side of the magnets.  Would the distance at which it started to point toward the disk be a meaningful measure as to how well the magnetic field was being captured?

I'm still towing with the idea of a 3 rotor 2 stator design.  The center rotor(s) would all have the same magnetic orientation as one of the end rotors, and would not need (or want) the iron disk.

So to convert from a 2 rotor to a 3 rotor, all you would have to do is pull off the outer rotor, insert the extra rotor and stator then reinstall the outer rotor.

[Tritium]

Usually 1/2 magnet thickness you plan to use is enough for the rotors though some get by with less. The plates sold on our host site www.wondermagnet.com are 1/4" thick and are made for 1/2" magnets

Thurmond

[esc]

OK I see that the dual stator triple rotor has been covered in other posts, so I'll drop it here, and try to stay to my own topic: a simple, cheap, first windmill project.

 

[esc]

So if I used (for example) the HF 3/8" magnets I would need about 3/16" for the rotor plate?  But since they are not as strong as Neos, could I get away with something even thinner?  Maybe 1/8"?

At that thickness I'm getting pretty close to being able to use old coffee can bottoms.    Or, more realistically, some other easy to find scrap.

[esc]

To get back on track here, an inexpensive first windmill project:

OK, even though I have been warned against it by several, I'm still considering the HF magnets.  60W in a 15 MPH wind sounds OK to me for this project.

I need to find a good cheap supply of magnets wire.  Old TV's and Microwaves sound like a reasonable source for recycled wire, but right now I would rather buy it new than have to mess with trying to find it.  But I will keep those sources in mind in case I come across any old TV's or Microwaves.

Does anyone know of a national chain store that sells reasonably sized (and priced) magnet wire?

I'll hit my friends up for any scrap PVC pipe and if that doesn't pan out I'll go buy a section of 6" pipe from on of the big box stores.  

I've read about using old car fans for the blade, hub.  I have a number of old "Flex Fans" laying around so I may look at using one of those.

I'm still looking for scrap iron to use for the rotors.

I'll probably make the alternator out of some 1" pipe (about a foot) with bearings in each end.  A section of 5/8" all thread will go through the center with the blades on one side and the alternator on the other.  All thread will allow me to bolt the blades and rotors just where I want them.  Then the support for the stator, tail and yaw bearing can all be welded on.  

Using the 1' pipe will allow extra space between the tower and the PVC blades to accommodate any flex.  The yaw bearing will be attached closer to the alternator.  I'm hoping it will balance about 4"s from the alternator end of the pipe and I will mount the yaw bearing there.

out of time for now, more later...

[Tritium]

Quote: So if I used (for example) the HF 3/8" magnets I would need about 3/16" for the rotor plate?  But since they are not as strong as Neos, could I get away with something even thinner?  Maybe 1/8"?

The rotor plates also serve as a mechanical element in the design. They must rigid enough not to flex when all the magnets are mounted and the air gap set otherwise they will rub the stator and damage will occur.

Thurmond

[ghurd]

The microwave transformers sometimes have larger wire, but I'll never bother trying to remove it again.  The wire is varnished into a nearly solid block!

TVs or computer monitors are a lot easier, and the wire is in much better condition.  It can be used 2-in-hand for larger projects.  And it's LE$$ painful if the project doesn't go just right!

Magnet wire is not common enough for the big box stores to carry.  Might pick some up at a motor rewind shop, if one is in your area.

The Dans sell magnet wire, Wondermagnet, top right corner of this page.

G-

[Jerry]

Hi Eric.

The low powered ceramic geny was being tested on a large battery bank. That means the voltage rize was small (Heavy load).

If I was in my test truck I may not have been able to write down all the info and at that point if I had to skip something it was the voltage reading.

At 15 mph with a simular size pma with NEOs would make 3 or more times that power.

If your talking about double stacking the ceramics power would only go up margenaly.

The blades are paterned after the Zub-Woofer blades introduced here on the board several years back.

People make those from very thin (1/16" wall) plastic drain pipe. Folks complain about those bending back and hitting the tower.

So I made a very simular blade but with the very strong none flexing foam filled pipe.

This pipe is filled with foam for thermal and structual benefits.

I think it was hiker that came up with the old saw blade as a rotor idea.

We were just searching for something cheap as a rotor. 1 blade was to thin so stacking up several made them thicker.

Problem is they are hard steel and stacked up that way also made for pour flux path.

Brake disc are cheap and easy and have very good flux path charicteristics.

But OH YA they are heavy. OH well free is a very good price.

[esc]

OK, the voltage makes sense to me now.

3 times the power is significant...but it would probably triple the cost of building the windmill as well.  Since high power is not really required for this project, I'm still leaning toward the cheap magnets ($0.50 at HF right now!).

I've never seen the "foam filled" pipe.  I think I will try some 4" PVC to make 3' to 4' blades.  I'm tempted to use 4 blades...but I wonder if a alternator built with HF magnets would be able to do anything with the extra torque?

I'm still searching for something cheap to use as a rotor.  I wonder if cutting them our of some 1/8" plate, and only using 1 piece would work?   I think it would be plenty strong.  How would the flux path be on mild steel?

[esc]

Microwave wire=big hassle.  Good to know.

For some reason I never thought of computer monitors.  I know where to get a couple of those!

I know "the Dans" sell it, and if I have to mail order it I will get it from them to support this community, but I still want to find it locally.  I do know where there are a couple of alternator shops locally that I might try.

Thanks!

[Jerry]

Using a single disc with ceramics would be a bad choice. There flux is very weak to begin with.

A single disc would make the magnetic flux circut even weaker (no return path).

Mild steel is the best choice for flux travel. So yes mild steel discs would be great. But don't use just one with ceramics. As a mater of fact I'm building a stator with powdered iron i the coil centers to improve the flux path on my 14-11 ceramic PMACeramics need all the help they can get.

You say your looking for as cheap disc as posable. Free brake disc are prety cheap. And they are local. Heavy though. I think 1/8" disc will work but 1/4" would be better.

I would not use 4 blades on this geny. Its a weak alternator and does not need extra tourque, it needs rpm. 3 blades will make better rpm. Since this is a small blade diameter machine with high rpm potential there will be more gyroscopic (SP?) problems with 4 blades during yawing.

                             JK TAS Jerry

[esc]

Sorry, I was not clear.  I meant 1 disk of the 1/8" mild steel plate per rotor.

I'll see if I can scrounge some 1/4" plate instead.  I do have 1/8" available and a shop next door that will cut it out with a plasma cutter for free.  So the price is right.

Yes, free disk brakes are cheap...if you can get them...but I have this other stuff that is also free and will weigh a lot less.  Not to mention it will be easier to mount on the 5/8" axle that I intend to use.

So 4 blades is more torque that I need, I thought it might be.  What about 2 blades?  They could be cut from 1 piece of pipe.

Thanks for all your help Jerry!

[wooferhound]

I got my Magnet wire CHEAP on eBay.

[Tritium]

 1 more comment on rotor plate thickness excerpted from the Dan's new book "Homebrew Wind Power" pp 74 "If you can stick a paper clip to the back of a magnet rotor, the steel is not thick enough for the magnet size you are using........"

Thurmond

[esc]

That is a useful tidbit!

[Rover]

Someone in here mentioned bridge rectifiers (Jerry)...I can't help with the choice in design.. but if you need bridges , I get mine from allelectronics.com .. surplus.. they have 3 phase full wave bridges for about 10$... 35 AMP.