# electric motors.



## gareth01422 (Apr 19, 2009)

Hi guys.

Just a simple question.

Would if make a differance if we used neo magnets in our electric motors or not.

Gareth


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## Morf (May 29, 2009)

Old but good reading relevant to your question on <Wired2.02:Charge!>. Try to hang on to the end of the last page which might be quite relevant. Cloud Electric LLC in Georgia will show you the Lynch Pancake style motors that are available from them. Other European companies by the names of Perm and Agni also have pancakes based mostly on the original design. The Lynch became popular in electric racing because of the brands economy, light weight, and I guess, reliability, since they ran over most everything else in electric motorcycles and carts. I am fired up over an attempt to built a larger pancake, that would be a torque monster, and would most likely need to cut back on rpm, which is not as important as ``lift off`` in my EV plan. The Cloud info. describes the pancade with magnets on one side of the disc or both, your choice. And the disc is to be made of material that is non conductive. I am anxious to see more photos of the inards of the pancake, and a good schematic. I also wish to thank the DIY fellow who submitted his thoughts about a large pancake that would lay flat between the frame rails and drive a conventional differential turned to face upwards. That rekindled a notion that I had thought about once and dropped. Hope the reading material has something you can use. Good Luck.


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## Morf (May 29, 2009)

A Design of a High Power Density Permanent Magnet Axial Gap DC Motor. This is the heading of a report from engineers at Oak Ridge some years ago. The paper is on line. To use a search engine to get into construction, theory, utility, etc. of this motor type, the key words should be `Axial Gap`, and not pancake, or Lynch, or the trade names of the European models. The computer model the Applied Technology Divison of Oakridge National Laboratory looked for this performance: 92 ft-lb at +-700 rpm (max. continuous). Max weight 120 lb. Package size-17 inch diameter x12 inches long, Battery supplied power. The length of this motor indicates the basic construction of the motor which has a single stator assembly with a rotor on each side of the stator. For each module, the stator would contain the copper windings, with a total of 21 slots. Steel laminations would comprise the `teeth`, but since the flux path is closed by the back iron in each rotor, there would be no stator `yoke` required. Cooling of the stator, to remove l2R-generated heat is easily accomplished by collant tubes since the stator does not rotate(!) Each rotor would consist of four rare-earth permanent magnets (SmCo or NdFeB) equally spaced in front of a back iron ring. The magnets and back iron would be contained in a non-magnetic, high performance engineering plastic such as `G-10`. They settled on an air gap of 0.55 in., and described magnet strength in kA/m, (at least 640kA/m). They continue on with their findings on flux density. Mention is made of the `new` neodymium-iron-boron magnets with Hc~900kA/m would increase this torque an additional amount without saturating the silicon steel teeth. Rotor temperature would be limited to to <-150 C.with neo., or 350degreesC with the SmCo magnets, and then they describe other limiting factors with the Sm heat numbers. The paper continues with approximately 18 pages of additional, detailed discussion concerning changes in size of the package, use of various materials and the consequences, and engineer Drawings of the Alpha Concept Engine. The conclusion in 4 points discusses an attractive option for future motors concerning the removal of all magnetic material from the stator and increasing the number of ampere-turns leading to a more power dense package, and the `upgrade` magnet consequence to this motor. A second Oak Ridge paper is `Back EMF Calculations for Axial-Gap Permanent Magnet Synchronous Motors(AGPMSM) with Disc Magnets which has graphs on waveforms at 973 rpm. Plus they have a photo of the an 8 pole rotor. I am looking for a work that would describe ideas about size(diameter) limitations. These papers above are the first such papers I have found concerning higher torque motors of this type. And the conclusions can be described as very positive.


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## Amberwolf (May 29, 2009)

Maybe you could start using paragraphs and some spacing between sections. It'd make your posts readable--right now there is far too much crammed in there without any line breaks, and I at least can't keep my eyes on the right lines while trying to read such posts.

I've posted some walls of text in my time, but they all have breaks between thoughts, so that people can at least try to read it if they choose to (I suspect most don't, just because of length).

I think that at least some of the information you post is interesting, but difficult at best to read due to being all one giant block of text.
________
Marijuana card


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## Morf (May 29, 2009)

Amberwolf,
Your criticism is valid and well taken. Are you interested in Axial Gap motors? I have a new document that looks at the moving of the magnets in Axials to change motor speed, a patent that looks very promising. Also newly found is a company that may do larger Axial prototypes. Best Wishes.


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## Amberwolf (May 29, 2009)

Moving the magnets? I presume moving them away from the rotor, as in increasing the airgap, would be what it does? Sounds like an interesting way to do things.

I've used a pair of axial flux pancake style radiator fan motors from a junkyard, with friction drive to one of my ebikes. The only real problem I had with them was that they were not designed for the side-loading put on them by the tire expansion as I hit bumps and whatnot, so the shaft on one snapped right where it connected to the output shaft bearing, on the inside of the motor. 

I had planned to rebuild a cieling fan motor into a radial flux hub motor at one time, until I found that the magnets I wanted to use would have cost more than just buying a regular bike hub motor. Since then I've learned a bit more about motors, and I wouldn't need such large expensive magnets, I think. 

That same CFM conversion I also wanted to try as an axial flux, after I had used the radiator fan motors, but I would have to totally redo the whole motor, which would make it fairly pointless to even start with a CFM except for the hollow steel shaft, bearings, and case. (some CFMs have tough steel shafts, though many are not strong enough to use as a load-bearing axle shaft). 

I've been subscribed to the Axial Flux yahoogroup mailing list for a while, but have yet to have time to read much of it. Same for many pages I've saved from the web here and there.
________
Liasel


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## Tesseract (Sep 27, 2008)

First off, I'm with Amberwolf on your formatting (the lack thereof, that is). 

I suspect there are some typos and/or mischaracterizations in here.



Morf said:


> ...
> The computer model ... looked for this performance: 92 ft-lb at +-700 rpm (max. continuous). Max weight 120 lb. Package size-17 inch diameter x12 inches long,...


Good grief - this is not what I would call _svelte_: 10# per hp?! 17 freakin' inches in diameter?!




Morf said:


> ...Cooling of the stator, to remove l2R-generated heat is easily accomplished by collant tubes since the stator does not rotate(!)


Well, that _is_ the definition of _stator_: the stationary part of a motor. 




Morf said:


> ..contained in a non-magnetic, high performance engineering plastic such as `G-10`


Are there any plastics that _are_ magnetic?

Otherwise, I am familiar with G-10 as the old designation for a fiberglass/epoxy composite used to make pc boards (now called FR-4) - is there another - plastic - material called G-10?




Morf said:


> They settled on an air gap of 0.55 in.


Are you sure that isn't 0.55_mm_?? The smaller the air gap between stator and rotor the better the magnetic coupling between them. I can't see any reason why a motor would benefit from or need such a large air gap.




Morf said:


> ... And the conclusions can be described as very positive.


I have found that papers published by the national labs (Oak Ridge, Sandia, Los Alamos, etc...) REALLY need to be taken with the proverbial grain of salt. Those people hardly ever conclude anything negative in their studies (probably so they don't get nastygrams from "well meaning" (read: meddling) politicians wanting to know why taxpayer dollars are being wasted on "failures").


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## Morf (May 29, 2009)

Hi Tesseract,
Located on the first line of the post we are discussing, I thought it a good idea to give the exact wording of the name of the study for the search engines. Next thought was to give keywords, Axial Flux/Gap, so persons could get in the right neighborhood of larger Axials, rather than using pancake or Lynch, which sidetracked me for a while. This study in question is a 20 page pdf report with charts, tables, and lots of math. My hope was that readers might find something of interest in some of the highlights I mentioned, and come back with their take. I would not have talked down to you by defining a stator, or make a case for non conductive plastic. 
This was my first finding of an axial torque `monster`. Now I am reading about axial engines for moving ocean liners. The report is a decade old. The basics that the report covers are like an Axial 101 short course for me. Last night I found AXCO-MotorsOy in Finland that has an information ad on Axials with photos that is packed with information for the general public. I have a request in asking for more information and motor pricing. Thirty -seven KW and 45KW (they also have a 250), at speeds of 8000-10000 rpm unless I was too sleepy to get that right. Please let me know what you think of AXCO. 
I will try to do better in generating interst for a chosen topic. I will stay away from quoting studies for submarine service motors, as the post in question dealt with. Thanks for your comments.


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