And so it begins

[ChrisOlson]

Chris, thank you for sharing that video.   

You're welcome.  I was beginning to think I had deleted it or something.  I know that when I made it I sent it to Hugh and Flux to watch.  Hugh commented that he had always wanted to try that but that all the "science" says it's "bad".  But what the "science" failed to predict was that you get flux that "leaks" out the perimeter of those rotors anyway.  This is evident if you build a turbine and use steel stator support bolts that are very close to the rotors.  The generator will actually "cog" because of the flux that leaks and attracts the steel stator supports.

Putting those on there, or machining rotors with a lip merely stops some of the normal leakage that you get at the edge of the disc.  So I hope this helps clear up some of the "old wive's tales" about how "bad" this is.  Sometimes these things get propagated as "fact" and somebody that realizes that it's just not right has to challenge it.
--
Chris

[ghurd]

Thanks ghurd. I've been having trouble trying to visualize the aerodynamics of the blade, now I have more to think about. I can't quite get my head wrapped around the relative wind hitting the airfoil on the bottom (very high AoA) then the transition to rotational motion with a frontal relative wind. Sometimes I think I have a grasp of it then it slips away. It's the transition that gets me. It'll click eventually. At least now I know what people are talking about.

jlt: I saw that on the "other" site. Seems like a pretty good trick. Any drawbacks to cutting the groove? I don't have any welding equipment though I can silver solder using propane, and I have a broken band saw blade laying around that I was going to repair, though that's a very high carbon content. I think I've read of problems with high carbon steel laminates.

You know a plane must be moving forward (relative to the air) to lift off, right?
Lets say it takes 50mph to create enough lift to lift/take off.
If the plane is on an aircraft carrier moving 25MPH, then only need 25MPH more speed?
But if the plane has 55MPH wind straight up from the bottom, then it is a different story.

It is not the transition, it is the AoA.
Yes, I know I didn't explain it worth a hoot.

"paper clip video"
Lets see if I understand what you are saying...

Without the claw, the flux is NOT shorted (can't argue with that).
And the paper clip hangs.

WITH the claw, you can no longer hange the paper clip.
Looks like WITH the claw has less flux in the disk, and the only place that flux has to go around is through the claw.
Since it only has a path through the claw to go around (in the video), then the flux IS shorted through the claw.
Since it IS shorted through the 'claw', then there is less flux in the coil
Since there IS less flux in the coil, then there IS less voltage, and less power.

The claws are helping to direct the magnatism to a shorted condition, which makes no power.
It is not going through the back side of the plate, it is simply wasted in the "claws".

If the paper clip sticks, then the disks are not thick enough.
Making the magents less effective (shorting their flux) so a paper clip will not stick is like cutting the legs off a sprinter so he will not run as fast.  Sure, he will not run as fast, but that doesn't make him more efficient.

I had a guy tell me his solar panel was not working as well as it should.  The problem, as he explained it, was the wire was too fat.  It took too much power to push electric through that fat wire, and skinney wire was easier to push power through, he said, because the power didn't need pushed through so many pounds of wire.
His explaination made sense to him.  It was totally incorrect, but it made sense to him.
He did not understand what he was doing.

[ChrisOlson]

The claws are helping to direct the magnatism to a shorted condition, which makes no power.
It is not going through the back side of the plate, it is simply wasted in the "claws".

That's not how it works.  All the plate does is provide a medium, that's better than air to complete the magnetic circuit between poles.  Except the pipe that carries the flux has a leak in it.  All the claws do is plug the leak.  I will quote Flux himself here, as I don't think he'd mind, and he and I and Hugh discussed this at length when I did it:
"There is significant leakage flux with the wide air gaps of these dual rotor machines which you won't avoid and some tinkering with the path of these leakages will have virtually no effect on the real gap flux."

He did not understand what he was doing.

If that's a hint that I don't know what I'm doing, at least I'm doing it so other people can see how it's done.
--
Chris

[Janne]

Chris,

The claws you have are not "plugging a leak". In fact, as Ghurd stated they're making it worse. In addition to the magnetic circuit between poles you mention, there is a local magnetic circuit for every magnet, between it's own N and S pole. In the paper clips-video the claws are not enhancing the inter-pole magnetic circuit, it just increases the local leakage magnetic circuit. As a result, the magnetic flux in the plate is reduced enough, so that the paper clip is not sticking anymore. The real solution is to increase the plate thickness, so that there is no leakage behind the plates, as Ghurd stated.

[ChrisOlson]

I have conclusive proof that it does not alter the magnetic performance one bit in the air gap.  When you place those magnets at the edge of a rotor the flux lines do not go directly from pole to pole - they bend.  There are some lines that bend outside of the active air gap.  I invite you to assemble a generator and model it with a gauss meter yourself like I have done.

All those claws do it stop some of the lines that bend outside of the active air gap from doing so.

I have built seven of these ferrite magnet generators so far - they all have "claws" on the rotors.  The latest one develops 3 kW continuous, without overheat, @ 100 volts and is only 12" diameter.  You can't make too many stupid mistakes, like "shorting flux", and get that kind of performance from a 12" axial with ferrites.

Edit for correction: The three phase 16 pole generator shown in the below photo is a 14".  The dual stator two-phase units I built with ferrite magnets are 12".

The rotors in that latest gen also use another concept that is supposed to be "bad", and that is crowding poles like this:



Except that crowding poles so there's minor leakage at the corners also has negligible effect on real gap flux and allows dropping the internal resistance of the winding by using a different coil geometry.

When it comes to this type of stuff there's always going to be "armchair quarterbacks" that can come up with all sorts of "wisdom" and tell how it "should be", and maybe some of them have even built a "book design" generator once.  Then there's the guys that actually play the game and got hands on experience with what works and what doesn't.  I don't follow the book.  I design and build my own stuff simply because I enjoy exploring the outer limits of what can be done and what can't.

And that's exactly where this comes from - experience and hands on testing.
--
Chris

[tomw]

Well, I have heard it said that years in the library can often be replaced by an hour or two in the shop...

Sadly, this stuff gets regurgitated over and over and eventually becomes misrepresented as a fact simply because it has been restated so much.

Not sure what your paper clip test shows but any with:without comparisons in use should show the reality.

I also think the game really changes with the lower power magnets.

So much flux in a NEO that a bit of diverted flux is perhaps a non issue as well as strong enough to go where it cannot in a weaker magnet?

If I had a dollar for every "fact" I got from a book / theoretical education that was later proven to have fallen from the south end of a north bound bull I could easily buy a dual rotor alternators worth of of big NEOs.


Interesting discussion. Glad to see the old bulwarks of [perhaps]misapplied theory being chiselled away!

Chris; Should you ever decide to produce these to sell I would love to give one a try. Really curious how they would work if tailored to heating water with common high voltage water heater elements. Always seem to need heat in some form or other. Bathing, planned hot tub, heating spaces. Our windy months are also heat demand heavy months.

I am no builder but find this stuff very interesting. Keep it coming. K.I.S.S has its place but can lead us into stagnated pools of design.

Thanks for posting this great stuff!

Tom

[ChrisOlson]

So much flux in a NEO that a bit of diverted flux is perhaps a non issue as well as strong enough to go where it cannot in a weaker magnet?

When I got my gauss meter I tested some neo rotors that have 2 x 1 x .5 N42 bars and the leakage on those is pretty severe.  It's way less with the big ferrite blocks.  Once you put two rotors face to face, with the ferrite blocks I had .120 Tesla @ 1/2" from the perimeter of the rotors and .167 in the air gap.  With the neos I had .350 @ 1/2" from the perimeter - over double what the ferrites got in the air gap.

With ferrites you really cannot make ANY mistakes in construction or design or it won't make any power.  To put it in perspective, take a "book design" neo generator with 1/2" thick x 2" round mags and open the air gap up to 2-7/8".  Now, try to get that generator to make some power.

Chris; Should you ever decide to produce these to sell I would love to give one a try. Really curious how they would work if tailored to heating water with common high voltage water heater elements.

I do build these machines for other people who can't build their own and want one.  My clipper is a three-phase delta configuration of standard off-the-shelf water heater elements and I got a pretty good match on that to the available power.  With a Classic it's necessary to have that because when the bank reaches absorb (and especially float) the controller simply unloads the turbine and lets it speed up to the point where you have the clipper drive set for, then it engages the clipper to keep the turbine out of an over-speed condition.

So I think it could be done on pure water heating.  It would take a careful match of wire run resistance with the elements to get it so it matches available power.  I don't think you'd ever get the same accuracy in power tracking that you get with a Classic controller, however, and I think it would be only be suitable on an excellent wind site.  What happens is that the clipper tends to work good, and provide a good match, to shaft power at really decent wind speeds (where it's needed most to control over-speed).  But when the wind dies down the clipper grossly over-powers the turbine and stalls it.

That would be an interesting one to try to work out the details on because I think it would require a "staged" loading system to let the turbine get started.   
--
Chris

[ChrisOlson]

To get this back on-topic for Kevin (because he's got a turbine to build), I did some figuring on the magnet configuration, just for giggles.

Somebody had mentioned putting them in a "T" fashion on the rotors to increase the surface area of each pole.  This works really good and I've seen other generators (like one Russel built in Ireland) where this has been done with great success.

If you used 32 magnets (two magnets per pole, per rotor) and built a 8 pole 6 coil, you will not get as much from the magnets as using the same 32 to build a 16 pole 12 coil.  The doubled surface area of each pole does not have the same power yield as 16 poles with half the area.

Part of the problem is that when placing them in a "T" configuration the width of the top pins in the coil winder has to be increased to take advantage of it.  You have double the number of turns per coil that you have with a 16 pole at half the area per pole.  Since the outer turns in the coils add turn length faster than the inner turns, it ends up losing out to using one mag per pole, per rotor.

The most powerful configuration I can come up with, using what you have, that should be a fairly close match for a 5-6 foot rotor is using all 40 in a 20 pole 15 coil generator.

I think that had already been decided earlier.  Just wanted to point out that doubling up magnets on poles to get double the surface area usually can't match efficiency using the same magnets to build with twice the poles at half the surface area.
--
Chris

[ksouers]

To get this back on-topic for Kevin (because he's got a turbine to build), I did some figuring on the magnet configuration, just for giggles.

Thanks, Chris, but I was enjoying the arguments. It was pleasant to see everyone defending their positions while remaining civil.

I need all the information I can absorb at this point, so these kinds of debates really give me a lot to think about. With several successful generators flying, it would seem whatever distortion in the flux field the cleats or claws may create is really insignificant. Therefore I have no worries about mounting the magnets in a shallow groove.

OK, the plan is a 1/4 inch thick rotor 8.500 diameter with a .030 deep groove to mount the magnets in. That should leave about a .134 wide rim to retain the magnets, and an absolute maximum of 6.388 inches for a hub. I may go 3/8 thick on the rotors. I'll have to call my friend and see if they have it in stock otherwise I'd have to order it. I can get 1/4 inch rotors water jetted for time and materials plus a six pack as they don't normally do custom work.

I'm thinking about a 3 inch diameter chunk of carbon steel for the hub, 3/4 inch diameter for the spindle. Any suggestions for bearings? I'm thinking radial load would be better, I won't have to deal with incorrect pre-load. I can stack them up say 3 per rotor, 2 inside and 1 outside, total of 6 bearings on the hub. Or would a pair of double-row bearings per rotor be better?

Thanks,
Kevin

[ksouers]

You know a plane must be moving forward (relative to the air) to lift off, right?
Lets say it takes 50mph to create enough lift to lift/take off.
If the plane is on an aircraft carrier moving 25MPH, then only need 25MPH more speed?
But if the plane has 55MPH wind straight up from the bottom, then it is a different story.

It is not the transition, it is the AoA.
Yes, I know I didn't explain it worth a hoot.

ghurd,
I think I got a handle on it now. The trouble I was having was visualizing a stationary blade with wind hitting directly on the bottom, then having the blade start to move and that wind change to a relative wind with a forward component over the leading edge. I ended up thinking about an airplane in stall (something I'm familiar with) where you have a high angle of attack and the airplane is falling downward, basically the same configuration as a stationary blade. As you lower the nose (lower AoA) you start to get a relative wind component coming over the leading edge, just as you would when the turbine blade begins to move. The airplane also picks up speed and the relative wind becomes even more horizontal, or a more forward component, again reducing AoA further.

Anyway, that's the way it finally made sense to me.

Thanks for all the help.

Kevin

[Bryan1]

Hi Kevin,
             With my 4kw motor conversion I counterbored in 84 16mm diameter bores 1mm deep so I could mount the N50 grade 16x13mm thick round Neo's. I found by seating each one in the counterbore held it snug and one the first pole I was pretty scared all 22 neo's would go flying out but they stayed firm. I do that now with with all my wind generators and will do in the future. By having  a pocket machined in the right place does make it easy for both placing the magnets and most of all purfect alignment of the magnets.

Regards Bryan

[ksouers]

Thanks Bryan. It's great to have other confirmation that recessing the magnets isn't detrimental to performance.


Kevin