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Forum Index : Windmills : Yet another axial

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ChrisOlson

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Joined: 19/01/2010
Location: United States
Posts: 60
Posted: 12:54pm 19 Aug 2011
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  Raptor50 said  
Has the prices gone thru the roof the last year or is this something that has happened over a few years?


It's basically been since about February since the prices really went up. But the problem has been brewing for 2-3 years with China reducing exports and manufacturers riding the wave. The problem finally reached critical mass and it's basically a problem of supply and demand.

The ferrite alternative works perfectly fine. I am extremely pleased with the performance of my ferrite machine and the only reason I did it is to prove that it can be done on a 3.8 meter size. Not even Hugh Piggott has ever built one that size. The smaller the machine, the easier it is to adapt a ferrite design.

Some of the problems are that the power curve with ferrites is typically pretty shallow compared to neo so the machine tends to run faster. The fact that the machine runs a bit faster yields better rotor efficiency and usually less peak power than a comparable neo design. But it can be done if you break some of the "rules" of axial design and think outside the box a bit.

Hugh has a recipe for an 8 pole three phase 12 volt in his PMG manual from back in 2001. But it is one of the only tested designs I know about for homebrew machines that uses ferrites.

I don't expect that the price of neodymium will come down any time soon because the demand in the computer industry, and others, is not going to go away. The manufacturing sectors that depend on rare earth materials are not light enough on their feet to redesign products to use alternatives, and that includes the majority of the wind power industry.
--
Chris
off-grid in Northern Wisconsin, USA
 
Gizmo

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Joined: 05/06/2004
Location: Australia
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Posted: 11:29pm 19 Aug 2011
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Well I'm having a problem.

Took the lid off the mold yesterday morning, the epoxy had set hard and it all looked good, just a few bubbles and valleys that needed filling. So I mixed up another batch of epoxy, popped the bubbles close to the surface, filled them and the valleys, then screwed the lid back down.

Its not setting Its been 24 hours now and this latest epoxy mix isn't setting hard. I've tried heating it, leaving it out in the sun, etc, but so far its still not set. It has the consistency of cured silicon, I can press my fingernail into it, and the surface feels wet/slimy. Any suggestions? Is it possible to dissolve the uncured epoxy out and try again?

Here it is with the lid off, out in the sun again to try and make this stuff set.




Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
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mac46

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Joined: 07/02/2008
Location: United States
Posts: 412
Posted: 11:42pm 19 Aug 2011
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Hello Glen,
If it were me, I'd just let it set for a few days and see what happens. Is it possible that the hardner did'nt get mixed strong enough? While pouring a large batch a guy can cut back on the hardner to help control the heating, but with small batches for patching I mix it pretty strong. It should set hard in time, how much time ...I don't know, 3 days to 3 weeks.
I am getting a real eye full of the candy...looks sweet, I'm tempted to try one of my own
kind reguards....Mac46
I'm just a farmer
 
niall1

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Joined: 20/11/2008
Location: Ireland
Posts: 331
Posted: 12:06am 20 Aug 2011
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hi Glenn

if the touch up work with the epoxy isnt going off , i,d be inclined to give it a good wash off with an alcohol based solvent ,release it out of the mould and try again when its clean....car bondo is good for cosmetic work...

the stator looks really neat from the pic ...i wonder if some of the release agent has got mixed in a bit with the last touch up pour of the epoxy ?....

epoxy seems a little more critical in getting its mix right than vinyl ester or poly ..
but as long as the main pour with the glass cloth is sound everything should be ok ..

with all those coil islands getting it out could be interesting ...

it looks very neat and exact from the pic ...




niall
 
Gizmo

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Posts: 5078
Posted: 12:18am 20 Aug 2011
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Hi Mac

After building this one, all I can say is unless you plan to build something up around 1kw or more, dont! This one is a prototype, a few idea's thrown together, and I dont expect a lot of power, less than a F&P. But its been a real money and time sink, and its still not finished.

I build another similar sized axial about 8 years ago, the power was OK, about 300 watts, but it took days of work to make. Ever since then I used F&P Smartdrives. I could pick up a complete F&P for $0 to $50, and it was ready to go, no winding coils, pouring epoxy, mounting magnets, etc. The F&P did have some issues to sort out, but it was tough, cheap, and easy.

A F&P is good for 200 to 400 watts, a dual for 700 watts. Its when you need more that the axial starts to makes sense. The axials scale up well, and if you want a 1kw or 2kw turbine, then building a axial to suit is worth the time and money.

This is just my opinion. I'm self employed and dont have a lot of free time, so time is important to me, and this little axial has sucked up a lot of it. But it has been a learning experience and I'm glad I've done it, even if it doesn't work.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
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Gizmo

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Posted: 12:23am 20 Aug 2011
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Thanks Niall

I'll give it a day and see how it goes. I dont really have much choice, the non-curing epoxy is in all the nicks and crannies around wires and coils, I wouldn't be able to dig it out, and I'm worried if I use a solvent if it will affect the cured epoxy from a day ago.

It was a structurally sound before this latest mix, I just wanted to fill some holes and make it look its best.

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
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ChrisOlson

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Joined: 19/01/2010
Location: United States
Posts: 60
Posted: 03:52am 20 Aug 2011
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Glenn,

I don't know what sort of epoxy you used (I may have missed that in my reading of the thread someplace). With fiberglass resins, if you do that, the stuff will never cure. I've tried heat lamps and even spraying the surface with MEK. The MEK will react and harden the surface but it still stays soft underneath.

Any time I've had that happen when doing fiberglass work I found the only real cure is to scrape out what you can, wipe it down with acetone and do another hot mix over it.

--
Chris
off-grid in Northern Wisconsin, USA
 
Gizmo

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Posted: 03:57am 20 Aug 2011
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Hi Chris

Yeah doing that. I've dug out most of the goo and cleaned it up best I can. I'll mix up some 5 minute epoxy to fill the holes and seal any goo I couldn't get to.

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
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Gizmo

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Posted: 04:55am 20 Aug 2011
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Using Bob's compressed air suggestion, the stator poped off the mold easily, but jammed up on the coil centers, so I used a chisel to give me some grip on the edges and it came apart without any drama. Only one of the coil centers broke off.







Now I'm just filling a few holes with 5 minute epoxy and then I'll drill the mounting holes.

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
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vawtwindy

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Joined: 23/10/2010
Location: India
Posts: 31
Posted: 06:11am 20 Aug 2011
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thats more of art work gizmo, greetings to you. eagerly waiting for its result too.
 
shawn

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Joined: 30/03/2010
Location: New Zealand
Posts: 210
Posted: 06:48am 20 Aug 2011
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For its size its all copper should be about as good for cooling as this type sttator can be, good stuff!!
And yes mine has also taken alot of time but it will bring you plenty of satisfaction.
Did you mention the type of blades you are going to put on this machine?
 
Gizmo

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Posted: 07:22am 20 Aug 2011
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Thanks for the comments guys.

More pics. Fitted the 2 stator plates. These bolt to each side of the stator to give it its strength and keep it in shape if it gets warm. Epoxy or resin can get soft when it gets warm, like when the alternator is under load, and deform, leading to the stator rubbing against the magnets. Hopefully these plates will stop that, plus provide the 3 mounting points to the stator bracket, which is welded to the 25mm center shaft. The 3 threads will allow me to position the stator with respect to the magnet plates, not in this picture. I can adjust the stator position and magnet spacing without pulling the alternator apart.







Next I need to reposition the magnets on the magnet plates. This thing has grown in diameter by about 10mm since I make the magnet plates, so I need to make a few changes. A job for tomorrow.

Shawn I plan to use a set of timber carved blades. I'll need to confirm the cut in RPM once its assembled, but I'm expecting up around 180 to 200rpm, so need some high speed blades.

Glenn


The best time to plant a tree was twenty years ago, the second best time is right now.
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Raptor50

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Joined: 17/08/2011
Location: Sweden
Posts: 8
Posted: 11:51am 20 Aug 2011
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I am Really impressed by the result of your stator.. I just LOVE the disign you ended up with. Has to be the stator with the best cooling ever.. :)
Keep up the good work Glenn..

I wish the day had more hours..
 
Rastus

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Joined: 29/10/2010
Location: Australia
Posts: 301
Posted: 09:03pm 20 Aug 2011
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Hi Glenn,
Apart from the time taken to get the mill to this point,a lot of planning and thought is demonstrated in it as well.It's like you've been sitting on a treasure and now sharing the find with all the other prospectors.For a guy whose pressed for time,there's still been room for a few flashes of brilliance!I hope the lower strength magnets plus layout add further to keeping the epoxy in the "cool" range.Cheers Rastus
see Rastus graduate advise generously
 
Gizmo

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Posts: 5078
Posted: 07:32am 21 Aug 2011
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Again thanks for the feedback. Yes its a design I've wanted to try for a couple of years now, but I havn't had a workshop set up to do anything. Since I decided to sell my place about 4 years ago I've done very little on the windmill front. Instead I've been packing, moving house and living in rentals for the last 2 years. Anyone who knows me knows I'm iching to get back into a place of my own so I can start making stuff again, I hate living in rentals.

Anyway, more done today. I CNC'd out some 7mm ply into a magnet positioning plate. It has holes to position the magnets and will be a permanent part of the alternator, though I'll need to seal it to make it waterproof before it see's full time service. Then I assembled the alternator, I was getting impatient to see if it was going to work.

This is the lightbulb moment. Its driven from my lathe at about 150rpm and there is a 5w 12v lamp across one phase ( 4 coils in series ).



Ran it up to test speed and I was getting 40vp-p cross one phase at 225rpm. Thats 20v peak. In a 3 phase star configuration, that would be 34v. Working back, I reach a 12v/24v cut in RPM at about 160rpm. Remember I have 4 coils per phase, so I can wire the thing for 12v or 24v operation. The figures are pretty close to what I worked out, lucky I'll check them again later to be sure.

What I want to do now is load it up, but I'll need to improve my set up first. I'm currently using a old cut up bicycle tube as my drive belt, and as soon as I short out a couple of the alternators coils it slips and grinds to a near stop.

Some pictures of the alternator.







Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ
 
mac46

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Joined: 07/02/2008
Location: United States
Posts: 412
Posted: 10:40pm 21 Aug 2011
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Hello Glen,
This project of you's is really comeing together. I'm impressed with the tight tolerances of the magnet to rotor clearances. The prediction of the voltage/amperage was spot on. This should be a "old realible mill" for several years to come, and probably a granddaddy of many more to be built like this in the future. Keep up the good work.
kind reguards...Mac46
I'm just a farmer
 
Gizmo

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Posts: 5078
Posted: 10:52pm 21 Aug 2011
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Thanks Mac.

One thing I noticed when I was testing it yesterday is the magnets need to be secured before I can do some serious loading. At the moment the magnets are using their own magnetism to keep themselves seated. The timber magnet positioning plate is stopping them sliding around, but when I applied a short to one phase I could hear the magnets rattle.

So today I'll pull the alternator apart, paint and seal the timber and steel parts, and then put it back together with the magnets glued in place.

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ
 
Trev

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Joined: 15/07/2006
Location: Australia
Posts: 640
Posted: 07:54am 22 Aug 2011
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Very good effort Glenn

Trev @ drivebynature.com
 
Gizmo

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Posts: 5078
Posted: 12:02am 24 Aug 2011
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More work done. Because I had to widen the stator slightly, I needed to move the magnet spacing bolts further out from center, so I elongated the bolt holes with a file.



And then tac welded some washers to position the bolts correctly.



I painted the plywood magnet positioning plates in epoxy to seal them from the weather.



A fully assembled and glued magnet plate.



Now onto the testing. First I tried a belt drive from my little hobby lathe, but as soon as I loaded up the alternator the belt would slip, so changed over to a direct drive.



Unfortunately my little lathe just hasn't got enough low down grunt to spin the loaded alternator much over 350rpm, and its minimum speed is about 220rpm, above the alternators cut in speed

I've managed to get a few figures. Using a 12v battery as the load, with the alternator wired for 12v, star. Cut in would be about 170rpm. At 325rpm I get 44watts. Wired for 24v in delta, cut in would be around 140rpm, I get 57 watts at 325rpm. I need to try 12v delta, cut in would be higher but the watts would increase quickly compared to star above that speed.

Plotting a few points on a graph, I'm guessing at 120w at 500rpm for 12v star, 150w at 500rpm for 24v delta, again on a 12v load.

Looking further up the graph, 300 watts is achieved at 700 to 800 rpm. Too high for a direct drive, but using a 1:2 chain/gear drive it would suit a 2 to 3 meter turbine at 350-400 rpm. But thats just guessing, I need to do more tests. My milling machine has a bigger motor and better low speed torque, so I'll see if I can rig it up to test the alternator at higher speed.

Coil resistance ended up at 0.6 ohms per coil. 12v star ( with a series parallel configuration ) gives a phase resistance of 1.2 ohms.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
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VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539
Posted: 12:57am 24 Aug 2011
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Hi glenn

Good to see it making some electricity, if you want to do some more testing you are welcome to use my lathe for trials.

All the best

Bob
Foolin Around
 
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