Aluminum roter [CLOSED]

[glaskote]

In about two weeks, we will run a test comparing axial flux dual-rotor generators with NdFeb magnets on aluminuim rotors. The test is to see if the same results can be achieved when compared to an iron containing rotor base by altering the magnets in varying configurations in accordance with Halbach theories. I'm curious as to whether or not anyone on this board has worked in this direction (and if they think we're crazy.)

Best to all

Glaskote

OK, glaskote. You were given ample opportunity to respond honestly to direct questions on exactly what you are doing. You apparently refused.


Story closed as a violation of the no Over Unity rule.


Failure to continue dialog honestly is also unacceptable.


Do not bother to repost without complete disclosure.

[mjc2002]

see my post

http://www.fieldlines.com/story/2008/5/19/124715/433

you might incorporate it?

and by the way...if you do...get ready to be "flamed" for thinking outside the "box"

regards

Mark

[mjc2002]

never mind

your ideas to concentrate the flux is great

stop wasting the other side of the magnet (like some designs do CURRENTLY) and use the halbach to focus flux lines to the active side

good luck

ps of course you will need to use cubes...correct?

[Flux]

Some like doing things the hard way, at best it may be nearly as good but seems pointless to me but I am stuck in the dark ages.

Flux

[TomW]

mjc;

and by the way...if you do...get ready to be "flamed" for thinking outside the "box"



Thats because, your own posts reveal that you do not have a clue what is in the box to start with. That makes thinking outside of it equal to "not knowing".

Lots to learn here unless you have already decided complaining is more important.

We tell it straight and we tell it true. If you can't take that kind of honesty then this may not be the place for you.

On the topic of Aluminum rotors and where he seems to be headed, I wish him luck but feel he is following a fairy tale mission. Time will tell.

Tom

[electrondady1]

fcfc did a lot of research into it

http://www.fieldlines.com/story/2008/2/25/24459/4156

[vawtman]

Whats the reasoning behind this? And whats the plan for securing the mags to the dual aluminum rotors?

[racer]

I have thought of building a generator using the halbach array. But the magnet shapes common on the market only lend themselves to making a radial design.

To the best of my knowledge one would have a very strange flux field with the inner diameter of magnets touching each other and the outer diameter of the magnets having a pretty big gap between magnets on a axial design.

[glaskote]

According to "Axial Flux Permanent Magnet Brushless Machines," using a core other than iron all but eliminates cogging, hysteresis, and eddy currents. It also limits the magnetic flux which is why the Halbach arrangement is necessary to increase and focus the flux over the coils.

The magnets will be attached to the aluminum that has been etched and alodined with a hi-strength hi-temp epoxy. They will be located and further held in place by attaching the aluminum magnet templates sold on this website.

[glaskote]

We had to have special magnets made up. It was expensive.

[glaskote]

Actually, not cubes but discs. We had the magnets made.

[TomW]

Tap, Tap. Wondering if you "get" how the flux in a dual rotor machine works? It has no iron in the core and it has massive flux density in the airgap.

All your idea is going to do is complicate things.

Look at the dual rotor machines. I think you are only considering a single rotor in your comparison.

Just slow down a bit and think.

I guess you are already in if you had magnets made.

I just hate to see you waste efforts without being fully aware of the options.

I guess its your time and resources but from here it just comes off as a half baked idea solving an imaginary problem.

Here is where the whole "thinking out of the box" bit gets cited.

I am very skeptical you are actually building a turbine. This subject is usually a prequel to some major breakthrough in over unity. We have zero tolerance for that.

Tom

[Flux]

I hope it is justified. If you understood the issues you are facing you would not need this approach. You look at commercial idea, don't understand it and then incorporate parts to solve a problem that doesn't exist.

Flux

[glaskote]

You're right. I do not have a handle on the terminology (I did post under 'newbee.) I should have said AFPM machine without stator and rotor cores. According to the book I'm reading on the subject, "a completely coreless design reduces the mass and increases the efficiency of the machine as compared with a conventional design." Further, "The-disc-type PM brushless machines without stator and rotor cores were first manufactured commercially in the late 1990s for servo mechanisms and industrial electromechanical drives, solr powered electricl vehicles as well as micromotors for computer peripherals.."

[luv2weld]

You really seem to be "hung up" on this "wasting half the magnet" idea.

Why don't you build it the way you envision and prove to us

that you're right???

Ralph

[glaskote]

We're building. Just waiting on the stator that we've ordered.

[glaskote]

[Capt Slog]

I've seen a couple of references to "wasted flux" recently, and don't understand. I never thought of it as wasted at all, I thought it was "returned" in a path by the thick metal of the rotors and that was the idea of the same?

.

[finnsawyer]

I finally Googled "Halbach Array" to see what the fuss was about.  It appears that by using 24 magnets of the proper shape and orientation of the field one could eliminate the iron backing the rotor and still maintain the flux path between the 12 resulting alternating poles in an alternator.  What is not clear is what the strength of said flux would be relative to just using the 12 pole magnets with iron backing to complete the flux path.  Also, one needs to also consider the extra cost of the 12 magnets with the poles on the side.  Simply going to a regular design using 24 magnets and 18 coils might be a better investment of resources.  Such an arrangement would need wedge shaped magnets, not the circular ones the Poster claims to have bought.  So, one wonders just what his configuration would be.

[luv2weld]

glaskote,

sorry the comments got put in the wrong order. It wasn't meant for you.

It was meant for the one that keeps harping on "wasting half the magnet".

Ralph

[glaskote]

The book I cited earlier describes disk, as well as other shape magnets arranged in a Halbach Array. The source claims (I'm quoting):

1. The fundamental field is stronger by a factor of 1.4 than in a conventional PM array, and thus the power efficiency of the machine is doubled.
   
2. The array of PMs does not require any backing steel magnetic circuit and PMs can be bonded directly to a non-ferromagnetic support structure (aluminium, plastics.)
   
3. The magnetic field is more sinusoidal than that of a conventional PM array.
   
4. Halbach array has very low back-side fields.
   
   

The point of all this was that from our standpoint, we are not so much interested in "not wasting magnetic field," but looking for a lightweight and easy to fabricate alternative to steel.

[glaskote]

Continuation to above comment:

Our thinking on the advantages of aluminium:

1. Lightweight
   
2. Stable (not susceptable to warping)
   
3. Easy to fabricate
   
4. Readily dissipates heat
   
5. Corrosive resistant (some alloys)
   
   

This bias comes from our evolving out of the aircraft industry. The high initial cost of aluminium may well offset any advantages from a homebrew perspective. On the other hand, there may be a homebrew advantage if a tried-and-true emerged that was less demanding from a fabrication and implementation standpoint. We're not looking to "revolutionize," just frogging around trying to improve (if we can) a very interesting and fun endeavor. Isn't that what discussion boards are for?

[joestue]

If indeed the flux density is 1.4x, then the Newtonian attraction is also 2x, so in a sense you doubled the magnet cost, and doubled the mechanical requirements.

If you want to build a lighter weight rotor combine aluminum/magnesium alloy with a thin mu metal ring behind the magnets.

Search the forum for photos of burned out stators, notice the extremely poor thermal conductivity of such, increasing the thermal conductivity of the rotor from 15-30 to 200 is not going to do much for a coil insulated in epoxy.

[glaskote]

Good stuff! What's mu?

[joestue]

search for mu-metal on wikipedia, though I doubt you need it at that price.

no seriously if you were to make a u shaped ring of aluminum with 2 discs of steel supporting the magnets, and cast the copper coil assembly with a much larger center cut out, you can cut the mass of the rotor at least by 60-70%.

The attractive force is contained to the inside of the ring, near the perimeter of the rotor, The center disc could then be one or two thin discs of aluminum or other composite.

[glaskote]

Thanks for your comments!

[finnsawyer]

What you seem to be missing is that half the magnets are doing no work.  By going to a conventional design with double say 24 magnets working for you rather than 12 you will get more than twice the power.  You should do some more research.

You certainly can back the array with aluminum or whatever with little loss of flux out of the poles.  But you still have to back the stator with iron to get maximum flux through the coils, and that is where hysteresis and eddy currents can occur.  The iron backing the rotor is not subjected to those issues anyway.  In a dual rotor, which I assume you are contemplating, there would be no hysteresis or eddy currents in the iron parts anyway, as all iron parts move in the same way (air core coils).

All that said, it is an interesting idea, but it seems you are greatly increasing the cost of the alternator just to get rid of the iron.  You should post a drawing of the alternator using the disk shaped magnets, as it is not obvious how that would configure, and I'm not going to wade through the book.

[glaskote]

I don't follow. How is focusing 24 magnets on a coil wasting half the magnets?

[joestue]

We don't have the ability to determine how much a benefit this is, or not.

Theoretically it can boost the flux density by 1.414, (the square root of 2)

in which case it increases the voltage by 1.414, doubling the power, for the same efficiency.

Theoretically, mind you.   without any theory, I can double the power by building a second alternator.

[ghurd]

The magnets wasted in making the array?

If it works out to 1.4x, then using a standard configuration is still a LOT better.

I thought the field increased by only about 1.3x.

The T is higher, but the frequency and surface area is lower.  Given the magnet material used.  Net loss?  And not just of money?

I don't understand 'why' anyway.

A standard dual rotor has no 'core'.

I can not comprehend what a PMA rotor 'core' is. ("without stator and rotor cores")

Seems to me a lot is being implied to the statement "The-disc-type PM brushless machines without stator and rotor cores were first manufactured commercially in the late 1990s"

Did they place the magnets on AL?  

More accurate, did they NOT place the magnets on iron?

If this is a tiny machine, then the magnet weight could go past weight savings of the AL.  

And I don't believe weight is an issue, because some of my tiny stuff is very (relative to standard dual rotors) heavy and it does not cause any problem I can measure.

If this is a large machine, then the blades need support.  AL has fatigue issues, meaning steel will be in there anyway.

I am not clear on if this is a dual rotor or single rotor with laminations.

A single rotor with laminations will have far more iron losses if T gets to large, and that machine will certainly be better with regular old school neos.

What problem are you expecting to avoid?

G-

[glaskote]

That's one way not to answer the question.

[glaskote]

See above.

[TomW]

G-;

I further submit that this is likely not a turbine alternator.

Every time this comes up it eventually becomes obvious the poster has been to keelynet and is actually building some bizarre machine to get power from nowhere.

This could be different but the complete avoidance of anything but the core idea in the face of facts leads me to believe this is NOT an alternator at all but some way to defeat physics.

Just an opinion because its so vague beyond the concentration of flux.

Notice the original poster seems to be completely ignoring questions specific to alternators and always gets tunnel vision on the flux.

This may be because the people here are extremely sharp and he knows the over unity crap is verboten so if you make it sound like it is an alternator you get fed information.

Personally, I think that if he does not clarify his alternator application of this that the thread should be closed as an off topic OU post.

Next, I expect him to get combative because I am calling him on the alternator design part of the idea.

Tom