Stator thickness on new design ??

[jarrod9155]

  Ok , cast my new stator for my solid shaft 20 foot turbine . I changed from 12 coils to 15 coils , the mag plates are 21 inches so it's pretty big mold . The problem I had with this cast was it was to be 5/8 thick , but the 14 guage wire would only compress to 3/4 thick . So now my my air gap will be a little bigger like 1 inch or so  . My new plates will have 20 1inch by 2 inch 3/4 thick neo mags . What I'm looking for is a opinion if a 1inch to 1 1/8 air gap is to big . 

[STYME JONES]

Do you have any pictures you could share with us? i would really like to see this beast. lol...STYME

[jarrod9155]

The 21 inch mag plates are gonna be back from the machine shop next week , I had the disk chucked on the hub in a cnc mill and had them mill out a 2 millimeter pocket were every mag goes . This should true up the plates plus add a perfect alignment  for the mags , when I get them back I will post the whole build . The stator has already started off bad I hope the rest of the project goes better . I did lower the resistance from 12.3 ohms to 3.2 ohms per leg . The new stator is 14 awg 160 turns per 15 coils , should of been 145 and I could of made the thickness down to 5/8   I got greedy more copper !!!!!!!!

[ghurd]

Usually the air gap should be about the thickness of the neo(s) per pole, maybe a tad less.
3/4 + 3/4 = 1.5"  or a bit less.
Sounds fine to me.

With 160 turns instead of 145 turns, it may need opened up a bit more than the 1.5" anyway?
G-

[jarrod9155]

That's was what I was looking  for , A base to compare from thank you ghurd . My aurora likes higher voltage so the closer the better . And I no it isn't thebest brake but all I use for brakes is the stator shorted  so more the brake the better . My 18 inch rotors with 18 awg coils over 25 mph winds could not stop my 20 foot blades , like it wasn't even engaged .

Jarrod

[tecker]

I use a magnet in a plastic tube in repulsion to get in the park . Before and after the coil leg covers the mag .If it's half or less  you should be good

[ghurd]

"the closer the better"

It is not linear.

There is only so much flux between the poles.

The difference between a 0.75" air gap and 1.5" air gap is not as large as you may be expecting, because the flux is still well linked.
3/4" difference.

The difference between 1.5" air gap and 1.75" air gap will be HUGE, because the flux is not linked very well at that distance.
1/4" difference.

Sir Flux (the man), and many formulia, call what you call thickness by the term "length".

You have a few issues that will get more complex than standard issues.
1st and formost, your Aurora inverter (which I honestly know nothing about).  A smart machine is 2nd guessing your 2nd guesses?
2nd and minor, sinking the neo 2mm into iron.  Not much of an issue for your machine, but it can get very bad for others.

My gut reaction is the stator should be about 1.35" thick (if something that dia can do it with a tight air gap), and the 'extra space' should be filled with the 'correct' turns of a larger gauge wire.
No.  I have no good idea what the 'correct' turns would be.
G-

[Dave B]

Jarrod,

  This is just my opinion based on experience with the larger machines. I have been down this road several times. I have crashed blades, I have burned stators. Over speed will do it every time and each time I could have prevented it with a closer airgap (more narrow stator) being able to stall the machine well before it takes off into the steep part of the curve. Once it's there and the gap is too wide you will never stop it even shorting it say nothing of an inverter stepping the load still trying to maximize the power. It's gone and all you can do is hope the damage is minor and nobody gets hurt.

  My opinion is to figure your coil gauge and windings to get your required voltage with a thinner stator to get those magnets closer together pulling like a bear at each other. Beef up the stator mounts so if and when you brake it it doesn't twist the stator into the magnets. Think about a Briggs 8-10 HP running flat out, that's what you are trying to slow down and control. If the magnets are not close enough because the stator is too thick, it won't matter what the voltage is, it will simply run away in the higher winds like there was nothing there. Good luck keeping it under control, furling becomes much less effective also when the output passes the controlling load. This is just another reason why everything happens so fast as you enter the steep part of the curve.   Dave B.

[jarrod9155]

Ghurd ,
             Do you see an issue with sinking the mags in the rotor plates ? I wundered  if this would effect the flux between the mags .

[jarrod9155]

   Dave ,
             Trust me I know how crazy things get 60 feet up that metal tower , a couple weeks ago engaged the short  and nothing just took off . I then engaged the dump load and the furling did the rest . Could of been a lot worse but  what I got from that was ether cut my blades down or build a bigger generator . As for the air gap that's right tighter means more controll and I was hopping I didn't have to scrap this stator ,20.5 pounds of copper  !!!!!

[Watt]

You could always try it. If it works that's great or change to thicker magnets later. Then, deal with those problems. Could u add amanual break for when you are around?

[ghurd]

2mm out of 3/4" is not so bad.

But some people have sunk them almost completely in iron.
Iron around the neo shorts the flux path.  The shorted flux does not go through the coils.
Mostly I was trying to keep people from machining 5/8 or 3/4" deep holes in iron for 3/4" neos.

Example.
Sort of simplified, and radial instead of axial, but you can see it in his photos if you find them...
Zubbly (RIP) could have just drilled holes in the armature for his motor conversions, but that would short the flux.
He turned the armatude down to allow for the neos, then fitted an aluminum sleeve over it, and drilled the holes in the aluminum.
Aluminum does not short the flux.  He also used fiberglass.

Behoof has some photos,
http://fieldlines.com/board/index.php/topic,129070.0.html

G-

[TomW]

A bunch of Zubbly's (RIP) photos showing his work on sleeved magnet rotors are archived over here:

http://pics.ww.com/v/TomW/FLRescues/Zubbly/

Tom

[Dave B]

  I figured you knew that already but I just had to share my experiences. I have done both in the past of what you say : cut the blades down and re-wind several different stators and all because I got greedy on thinking more winds of the thickest wire. You can get the voltage back up there with fewer winds and a thinner stator to bring the magnets closer and then have a little room to work the gap and still be able to stop that machine.

  If your hub is now seperate from your rotors this will isolate the bending of the rotors into the stator when there is a tight gap on a normal mounting of the blades to the rotor plates. That should allow you run tighter to the stator if you need to and not be as concerened with tearing up your stator with the magnets.

  Chris Olson has always said hanging rotors and blades on a trailer hub was not the best and with the larger machines this is certainly proving to be true with worn bearings, scraping rotors and stators then burnouts, shorts etc. etc.

  I hate to see stators here I'm not using but the investment I made the last time to change everything from the stator, voltage, load controller, blades etc. to control my machine has been worth all the time and money involved to do so. It's conservative, it's safe and it works, no buzz bomb here anymore and adding over 1KW of solar put the icing on the cake.

  Flatten out that curve and relax over 20 MPH, less power yes, less expensive and less stressful in the long run is well worth it. Good luck,  Dave B.

   Dave ,
             Trust me I know how crazy things get 60 feet up that metal tower , a couple weeks ago engaged the short  and nothing just took off . I then engaged the dump load and the furling did the rest . Could of been a lot worse but  what I got from that was ether cut my blades down or build a bigger generator . As for the air gap that's right tighter means more controll and I was hopping I didn't have to scrap this stator ,20.5 pounds of copper  !!!!!

[jarrod9155]

Thanks for the input Dave ,
         I hope to run the not so perfect stator next week I am hoping to keep the air gap down to around 1inch maybe a hair more . If the milling of the plates trues it up enough . And for sure the solid shaft has helped with the air gap , the old stator I had on this machine had the gap down to a little over 1 millemeter on each side . I hope to see more people try this setup instead of trailer hubs on bigger machines .