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Old Nov 16, 2004, 11:41 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,430 Posts
2.25 gram 6-pole and 3.5g LRK Outrunners

Here is a 2.25g outrunner that is a collaboration between Gail Graham and myself. It uses a 11.5mm diameter 6-tooth stator from a MiniDisc music player. Gail machined the front bell and flux ring. I did the final machining of the bell and also machined the bearing tube and motor mount, installed the magnets, and wound the stator. It's hard to appreciate the number of emails both ways planning and figuring out this motor. And, as usual, lots of machining advice flowed my way from Gail.

More details can be found on my MiniDisc Motor page.

Another motor that is a joint collaboration between Gail Graham, Mike Cross, and myself is a micro LRK. Pictures and details can be found on my Micro LRK page. Currently this motor weighs ~3.5g.

Neither motor has run yet. And, since I leave on vacation in two days, neither is likely to run till early December. At the present there is no light weight 1-cell BL controller. But, I know I have lots of testing and refining of the winds etc on both both motors. Since I do have a TMM controller that will operate on one cell I can develop winds for both one and two cell operation. I'm assuming if we build it they (1-cell controllers) will come.

Pictures shown below are of the 2.25g MiniDisc motor. But, the Micro LRK motor looks almost the same. That's a penny the motor is sitting on.

Gordon
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Last edited by Gordon Johnson; Nov 17, 2004 at 09:03 AM.
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Old Nov 17, 2004, 04:51 AM
My member is not
Zlatko's Avatar
Melbourne City Hlpt, Australia
Joined Jun 2004
759 Posts
Gordon,
Beautiful work again
I love the 12 pole LRK, that would be awsome fully wound
Cheers
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Old Nov 17, 2004, 05:24 AM
www.jmquetin.com
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Paris - France
Joined Aug 2003
195 Posts
Congratulations Gordon ! You deserve your holidays .
Jean-Michel.
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Old Nov 17, 2004, 05:49 AM
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billystiltner's Avatar
United States, VA, Clintwood
Joined Nov 2002
3,666 Posts
Gordon
I agree with Jean-Michael.
It looks awesome. Someone needs to build you a controller.

Billy
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Old Nov 17, 2004, 05:59 AM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
I thought you were quiet, well done!!

Very shiny too!!

Graham
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Old Nov 17, 2004, 06:14 AM
Registered User
QLD, Australia
Joined Sep 2003
1,550 Posts
Quax is developeing a single Lipo controller , the cct and software is available and a PCB is being developed -it will be released after testing .
You can get details here :- http://home.versanet.de/~b-konze/blmc_flea/blmc_en.htm
Stewart
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Old Nov 17, 2004, 06:50 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,430 Posts
Stewart,
I'm counting on Quax and others to have 1-cell controllers relatively soon. I've been following his progress. I think it's just a matter of time till we have a couple of choices in this area.

Here is a weight breakdown for the MiniDisc motor. The portion of the weight from components starting with "glue" on down the list represents the portion of the motor that does nothing to create torque. Torque is created by the stator, windings, magnets, and flux ring. The proportion of total motor weight coming from non torque creating components is approximately 22%.

These non-torque creating components were the ones we attacked like building a micro plane to analyze each one and see how light it could be made and still be just barely strong enough for its function. To this end I machined a few different trial bearing tubes/mounts to see how light I could go. I also have one failed front bell that determined how thin was too thin in the persuit of lightness. Even the shaft size is important. Although a 1.5mm shaft might be more durable, it would weigh 2.25 times as much as the 1mm shaft, and thus weigh ~0.20g instead of 0.09g. It would also require heavier bearings.

Gordon
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Last edited by Gordon Johnson; Nov 17, 2004 at 01:03 PM.
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Old Nov 17, 2004, 07:21 AM
Registered User
Tel Aviv-Yafo Sde Dov, Israel
Joined Nov 2002
288 Posts
Gordon
Looking great! Is it going to become a product soon, as a fully assembled motor or in a kit form ? or do we need to start searching for old mini discs to take appart ? In my mind I allready see sub micro 3D coaxial helicopters made with these motors... just what I was waiting for. Thanks for sharing all the info about it.
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Old Nov 17, 2004, 08:00 AM
pem
Registered User
Frankfurt Intl, Germany
Joined Feb 2004
291 Posts
@Gordon, Gail and Mike

Simply beauftiful. These designs line up directly with the interior of ancient watches
(those my grandfather repaired - me being a child.).

@nachman

usually minidisc players are still expensive - at the other hand they contain other interesting motors. Only a few contain stators - lot more are discrunners.

Peter Maul
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Old Nov 17, 2004, 08:11 AM
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Pete P.'s Avatar
South of Boston
Joined Mar 2004
846 Posts
Gordon: Why N45's? Do N50 grade magnets not come in that size?

Very awesome! You're going to make me one too, right? HAHA
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Old Nov 17, 2004, 08:17 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,430 Posts
Sorry. No commercial product plans. Commercial choices relatively soon will be Uttam's and his dad's 3.5g outrunner and Gary Jones' 7g disc motor.

Peter Maul is right about disc player motors. He and I traded a number of emails about this. Essentially you have to take a chance on a disc player not knowing if it will have an outrunner or disc motor in it. I got very lucky and found one on Ebay that had these stators in it. I then bought the remaining 5 players from that source. My average cost with shipping is about $15 per disc player. Along the way I bought a iPod hard drive for $45 only to find out that it has an inrunner motor not an outrunner.

If you want to do the LRK motor Mike Cross may begin selling stators for people who want to experiment on their own as we have here.

Experimenting requires at least a lathe and some specialized items like collets in the 2 to 3mm diameter size, tiny boring bars, and reamers etc. I laid in about $300 in new tools for my lathe to work on these motors. But, I probably got more sizes of various tools than was required as I really didn't know what direction it was all going to go (e.g., reamers in 0.005 inch increments are about $20 each, small collets are about the same, and collet holder and adapter are about $100). Our front bell weighs 0.16g. I'm pretty sure one weighing about 0.25g can be machined without CNC cut pie-shaped openings by simply boring four holes in the front. So, if one has a lathe and reasonable set of companion tools this is all possible. Unfortunately people are probably not going to be able to work on stuff this small with just a 3-jaw chuck.

N45 magnets were used as that's what was available in the correct size. N50's are only recently available in fewer sizes. Check out the magnets at Engineering Concepts. Can't buy what isn't there without ordering 1,000 custom magnets.

One other thing. The theoretical lower limit in weight for the mini disc motor is about 1.8g. Winding weight can be reduced by almost half by winding every other tooth. And, magnet weight can be cut in half by going with 4-magnet poles rather than 8, resulting in a loss of torque. But, it's unknown how well the motor would run in either situation and are for further experiments. Also, 0.08g can be added by going to 10 magnet poles, winding the stator differently, and going from a 4:1 turnaround ratio to a 5:1, resulting in more torque.

Gordon
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Last edited by Gordon Johnson; Nov 17, 2004 at 09:01 AM.
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Old Nov 17, 2004, 09:21 AM
Registered User
Gainesville, Florida, United States
Joined Sep 2001
1,456 Posts
Amazing work.
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Old Nov 17, 2004, 01:58 PM
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CA'ed fingers's Avatar
Montreal, Canada
Joined Feb 2003
1,907 Posts
awesome!

Can't wait for commercial versions for my conversion projects...

eric
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Old Nov 17, 2004, 03:01 PM
FASST flyer
KatManDEW's Avatar
USA, OH, Newark
Joined Sep 2001
3,563 Posts
Continually amazing Gordon.

I'm going to expose some of my ignorance here and ask what LRK means?
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Old Nov 17, 2004, 04:21 PM
Team30 Micro EDF
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Adelaide, Australia
Joined Apr 2004
11,200 Posts
ditto.
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