Wyatt needs more Power

[mitcamp]

Since then, Wyatt has recorded a average of 11 kilowatts per day on his Trimetric. He is in a good location and the windgenerator is spinning  most of the time, making 20 plus amps. Link here

http://www.fieldlines.com/story/2009/1/23/194656/301

Wyatt now wants a 2000 watt machine, figuring it would give him 40 amps at 24 volts and doubling his power.

I am considering the following as I could use a similar 15 or 16 inch disc.

1. ..  The use of 16 rectangle magnets on each disc 2 in. x 1 in. x 3/4 in. thick  or the 2 in. x 1 in. x 1 in. thick
   
2. ..  The use of 16 Disc magnets 2 x 0.5 on each disc.
   
   

I have searched the board and see little use of these thicker rectangle magnets, with the exception of the 2 in. x 0.5 in magnets that Dan B uses. I realize stronger magnets would require a different coil winding and a larger blade.

I am anxious to hear from anyone regarding the use of the thicker rectangle magnets, pro,s and con,s

 Flux and electronbaby comes to mind.

             Thanks all Mitcamp

[Airstream]

Neo magnets might be best measured by volume...

2 x 1 x 0.5 = 1 cubic inch material versus a 2-inch diameter round magnet volume:

Round magnet area = PI x (radius) x (radius) x (thickness)

= 3.142 x 1 x 1 x 0.5 = 1.5715 cubic inch of material.

Even a 3 x 1 x 0.5" magnet has less volume (1.5")

Perhaps you want to look at 3 in x 1.5 in x 3/4 inch or N50 2-inch rounds, with a larger rotor area you can fit more magnets?

[mitcamp]

Airstream, Thanks for the conversion, I have used the 2 x 1 x 0.5 rectangles for 3 years and never realized the difference.  If I were to build one for my own use, I certainly would go for the extra expense, thats for sure.

                          Mitcamp  

[Todd a]

I always liked this one...

http://www.otherpower.com/new17page1.shtml

It is a 17' that makes over 3000w.  You might scale itr back for a nice 14' or 15'.

[electronbaby]

I don't see why you couldn't use the 3/4 inch thick magnets. It will allow you to either have a wider airgap for more mechanical clearance between your rotors and the stator, or use less copper in your stator windings. If you kept the windings the same, you will cut in sooner, and most likely stall in higher winds. I know its different than most peoples goals, but I like to run in stall in higher winds. Things seem a little more well behaved. Not sure about Dan, but Hugh is using 16 inch rotors on his 12 foot designs. If you go to a 16 inch rotor with the 3/4 inch mags, you will see a substantial increase in power out.

We have had some crazy winds here this winter, and Ive lost two machines so far. It seems the props like to hit the tower during extreme furling circumstances. At first I thought it was happening while the machine was furling. Upon closer inspection it seems that Im having the problem while it is UNfurling. There is an abrupt movement as the tail slams back into the normal position causing excess gyroscopic forces on the blades and causing them to bend back and smack the tower. If I cant fix it another way, I will try Hughs suggestion of reversing the direction the prop spins.

good luck

[electronbaby]

oh, to make sizing the coils simple, just wind a test coil. You know how the other machine performed, and you know the voltage/RPM you need. Work the math backwards and make sure you account for rectifier losses. It should be pretty straight forward. If the magnets are of a similar profile, then the only changes you will make to your coils (granted you keep the stator the same thickness) is to have less windings. This might mean you can get away with using larger gauge wire.

watch your fingers.

[Flux]

It looks as though you want to jump up to something like 16ft to get twice the power in the same wind speed.

2 x1 x1 magnets will do it well enough. To use 2 x 1 x 3/4 I think you are pushing things if you insist on running in stall mode. If you are prepared to increase cut in speed and loose a few watts on virtually windless days then you may do it with the 3/4 magnets.

To use 3/4 magnets I would be looking at increasing disc size and using 20 magnets ( not sure if disc size is set in stone).

I can't easily model the 2" round magnets and I have never had any experience of using them. I suspect that replacing rectangular ones with those 2 " diameter really needs bigger discs, most of the designs using them seem to have them crowded to close together so disc size might be an issue again. Keeping the same disc size I don't think the 2" diameter ones will do it comfortably and if you go up to 20 the disc size is certainly too small.

You could look at bigger rectangular blocks but I can't do much without knowing what you might have in mind.

Simplest option looks to be 2 x 1 x 1  with coils about 1 1/8" thick. for similar cut in speed increase coil turns to 1.3 times the present.

I see a very significant issue with wire size for a 24v  machine. You will be needing the equivalent of 4 #16 in hand. The line loss is also going to be a big issue if it is any length. Unless you can keep the line loss down it is likely to get away from stall and you will have a different beast on your hands and you may get considerably more out but stator heating may become an issue unless you can control the furl.

For that sort of rating at 24v I wound my machine in 2 sections and brought 6 leads down to the rectifiers at the base of the tower, easier to wind but I was using a different construction and already had 3 wires in hand for each section.

Flux

[ibeweagle]

use 1,2,.5 or 1 inch thick but I have plans for a 16.5 inch rotor with magnet holders made from 14 awg metal glued on with epoxie 20 per rotor should be a great axial gen also coils are shaped like pie slice so max power out of stator e-mail if interested have done one with 12.5 rotors and 16 per rotor and flying for 2 years no burn out and outputs max peak was 42.3amps at 28 volts 12 footer ibeweagle@hotmail.com

[mitcamp]

Flux,Roy I appreciate your comment on the use of the rectangle magnets. I have not used the 3/4" or the 1" thickness. I might just go for the 1" thick magnets and be done with it. The 3/4" are N50 and the 1" are N42 and the cost is about the same. My rotor disc are 15" x 3/8" thick and I have them on hand. This would allow me to lower the generator and change both rotors and the stator, using the same frame. I will use a 14 or 15 foot diameter prop and increase the tail boom from 6 ft to 7 ft.

The previous stator windings were 50 turns of 2 in hand #15 and it worked well, condidering the windy location its at. I will use Flux,s winding scheme of 4 in hand #16  Flux says "for similar cut in speed, increase coil turns to 1.3 times the present"   Flux would you confirm the total turns per coil for this modification,Please.

 Roy, The offset of this 12 foot machine is 7 3/4 inch and 18 degree on the tail hinge. This machine is in a above average wind area. It runs much of its time fully furled. You mentioned your machine was furling properly, but then it slamming back hard enough to cause the blade to flutter. Is this offset or tail hinge degree problems or maybe tailboom weight.

I have been following stories this last 6 months regarding stator burnouts. So I have been more generous on offset and I reduced the tail hinge from 20 to 18 degrees. This 12 footer of Wyatts is in such windy area, its hard to tell. But it,s been up for 3 months, in a nasty place and it preforms nearly 24/7

                     Thanks Guys  Mitcamp

[electronbaby]

As far as the tail angle goes, I would err on the side of decreasing the tail hinge angle to maybe 16 degrees. Furling point can be set with tail weight (either adding or subtracting as needed) but I think I have to slow down the tail from swinging back into unfurled position. If you were to decrease the angle, then it would not travel so fast over the distance it needs to. The more commercially available machine I do nowadays, Im always amazed at how little force on the front of the prop to furl the machine and make the tail lift. I should have shot a video of the Bergey autofurl while I was playing with it. It would be really easy to see how well tuned this mechanism is. There is a very small alternator offset, and a very slight tail pivot angle. It unfurls VERY slow with no wind on the front. A little faster under operating conditions, but no way near the angle most axial flux guys are using. I also must argue FOR the way most of us do it. Pipe-in-pipe is very easy, and it can be made to work well. I hope I can speak for a lot of us when I say "its fun working out the bugs". Its not that often I see 80 mph winds to test in. :-)

[mitcamp]

Roy, I seen post on the board somewhere where they used a 1 way automotive shock to dampen travel.

I also was on site when a 10 Kilowatt Bergy was assembled and hoisted 85 feet to its perch and I couldn,t figure it would ever furl, but indeed it furls . My old Whisper 1000 still in use also furls with little force, although a mite noisy. Can,t seem to kill it after all these years.

On another note, on your 2nd post you wrote

"If the magnets are of a similar profile, then the only changes you will make to your coils (granted you keep the stator the same thickness) is to have less windings. This might mean you can get away with using larger gauge wire."

Flux says:

Simplest option looks to be 2 x 1 x 1  with coils about 1 1/8" thick. for similar cut in speed increase coil turns to 1.3 times the present.

I,m a little numb sometime and I need a big hammer to point me in the proper direction. It must be in the (granted you keep the stator the same thickness)

                   Still learning

                              Mitcamp

[electronbaby]

what were the dimensions of the magnets you used previously?

Maybe flux meant coil height? If you are using a 2" tall magnet. you will not need a 2" tall opening through your coil. Its ok to go a little smaller.

What stator thickness are you shooting for? Most people that use the 3/4" magnets use a 5/8" thick stator. You dont need to. You can use whatever you want, but what I would not do is make the stator thicker than the magnets themselves UNLESS you want to pick up a lot of high end wind performance, and run the risk of possibly over speeding. But again, you are using A LOT of magnet in this machine, so you will have to experiment a little.

If you want to run slow (in stall), then I would make sure the total air gap (between magnet faces) is less than the thickness of the thinnest magnet you are using. In your case that would leave an air gap of 1" overall, and in all practicality, you would want to go smaller, maybe 3/4". This would leave you enough room for a 5/8" thick stator. Ive yet to play with 1" thick neos (might be ordering some soon as the price has dropped on them substantially) but if it was me, like I said before, I would build up my magnet rotors, and wind a test coil and go from there.

[mitcamp]

Hi Roy, Wyatts 12 footer was hatched via Hugh Piggotts book plans, 16 mags 2 x 1 x 0.5 on each 15 inch disc, 24 volt stator, 3 phase, 12 coils, 2 in hand # 15 ga. 50 turns. Works great, except Wyatt wants more power. I,ve decided to go with the 2 X 1 X 1 magnets.

 He is located on high ground and has above normal winds, pretty much 24/7  " Low winds are Hang on to your Hat " and  "High winds are Hang on to the screen door when you open it, so you don,t blow away" He is going to get 95 percent of his power in above average winds.

This generator is not going to get much sleep  where it going, so the stator has to be bullet proof.

The day I finished the installation I released the brake and as I headed for town "I felt sorry for leaving it there"

                         Thank again Mitcamp