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Old Apr 30, 2013, 02:21 PM
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I sent these guys an email: http://www.permanentmagnet.com/

But if that doesnt work out, I'll probably just get a replacement motor.
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Old Apr 30, 2013, 02:46 PM
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Thanks for your help sneu.
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Old May 02, 2013, 03:34 PM
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Just got an email from www.permanentmagnet.com

12 N42 magnets 3.60/each
12 N45 magnets 3.80/each

$85.00 express (EMS?) shipping.

So $128.20 or $130.60.

Or I could buy a $122.95 (+shipping) replacement motor from a US vendor. But wheres the fun in that?
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Old May 02, 2013, 11:54 PM
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Have you removed the magnets from the rotor. I'm curios you list the height as 1.5mm I found I've measured magnets glued in I'll get some dimension like that and once removed find out they are really 2.0mm. I did the custom design on HKCM and the calculator will not allow for a 1.5mm height magnet any longer than 20mm, at 30mm long the minimum height is 2mm. I don't know if this is physical limit to all manufacturing of magnets or just HKCM limits. It may also be possible to put two 15mm magnets inline to create the 30mm. I've seen threads were they put to mags next each other to act like one magnet.
I did a search for the motor and found your posts on other sites, I guess you been working on this awhile. I noted folks being concerned about installing and balancing those steps are not to difficult. I have had no balance issues with motors where I've replaced the magnets. Although the Motrofly kits that require installation have had a problem but I think it's built into the bell. No worries though with a cell phone seismograph app will help if needed.
Looking back over your post on dimensions did you check the airgap, maybe there is room for another .008". That's the thickness of two sheets of standard printer paper
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Old May 03, 2013, 02:45 PM
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I've removed 3 of the magnets including the one that is broken. 1.5mm thick exactly with almost no glue on any of them. The little bit of glue left is easily scraped off with an exacto knife.

I'll check later on, but I'm pretty sure an extra .008 inch wouldnt make much difference. What did you have in mind?

I do have both pieces of the one broken magnet and they weigh almost exactly what another intact magnet weighed. Used an empty ritz cracker box stood on end to distance the magnets from my scale.

I have the same concern about gluing the 2 magnet segments together as I would about using 2 15mm magnets vs 1 30mm. Like poles repel, and it took quite a bit of force to keep those 2 segments next to each other. Should that glue detatch at 40,000RPM and 130 degrees F...

Btw, did u know an empty ritz cracker box weighs about 65 grams?
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Old May 11, 2013, 07:19 AM
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http://static.rcgroups.net/forums/at...g?d=1367782378
An example of using multiple magnets as one. Keep in mind that any magnet not attached will be ejected from the motor. If one mag can be attached with out coming loose regardless of load or rpm multi mags can be attached the same way.
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Old May 11, 2013, 07:53 AM
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Do those adjacent magnets have the same magnetic orientation? If so, what type of glue do you use to keep them from repelling each other and shifting?

Also I got an unusual number of replies from www.permanentmagnet.com. I did not respond to the quote they sent so they emailed me daily for 5 days afterwards until I told them I'm not interested.

Its these guys in case anyone reading is interested:

China Rare Earth Magnet Limited
Room No. 705-707, Tower A Century Holiday Plaza.
No. 9030 Shennan Rd., OCT, Nanshan District, ShenZhen , China
Post Code: 518053
Tel: +86 755 26923096 +86 755 86621665
Fax: +86 755 26915592


I cant imagine business is slow for them with the growing interest in our hobby, as well as E-bikes and hybrid cars. Maybe they are just that ambitious.

I'm mulling over gluing the 2 magnet pieces together. I already have some rubberized CA and I'm thinking the slotted gaps where the magnets fit into the can would help secure the broken magnet in place.
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Old May 11, 2013, 12:38 PM
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I have used CA with some degree of success, on motor's used for 3D. The 3Dmotor spends a fraction of the time at WOT. On motors that live at WOT I use green Loctite 638 and Loctite primer "N". The 638 will cure without the primer N but it takes like a week.
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Old May 11, 2013, 01:18 PM
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Thanks for the replies everyone. Btw, its Saturday. If at all possible, go fly something.

Zeroback I must apologize for my bad manners. Did you say a tree fell on your house? Yikes. I hope you got that sorted with not too much trouble.
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Old May 11, 2013, 02:07 PM
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Nobody knows the trouble I've seen
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Old May 11, 2013, 10:44 PM
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Quote:
Originally Posted by kavic5150 View Post
Do those adjacent magnets have the same magnetic orientation? If so, what type of glue do you use to keep them from repelling each other and shifting?
The adjacent magnets are oriented the same, and they are held in place with thin CA. The first four magnets were installed 90 degrees apart, and held in place by a very small drop to avoid buildup in the can. The second set required clamping to keep the magnets in place until the adhesive cured. Once cured, all of the magnets were coated liberally several times and the can was spun with a drill to distribute the glue more evenly.
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Old Jun 23, 2014, 12:20 PM
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Finally found a set in the right size.

http://www.ebay.com/itm/5-pcs-Very-S...item19ee41c6a5

And a set of digital calipers says 2mm thick on the originals so I'm good to go there. What I'm wondering is will the N52 rating affect the motors efficiency, I suspect the originals are more like N42s. I read that raising the magnet N rating also lowers kv if nothing else is changed.
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Old Jun 23, 2014, 05:18 PM
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Correct, stronger magnets wil give a lower Kv. And for a given rpm, both hysteris and eddy current losses (=iron losses) will increase a bit, leading to a slightly higher Io.

Vriendelijke groeten Ron
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Old Jun 24, 2014, 12:38 PM
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EDM = Electrical discharge machining

See wikipedia

This process can machine any conductive material including tungsten carbide. It can be very accurate.

It can cut holes of any shape in hard materials such as tungsten carbide .

A related process is ECM or electrical chemical machining which is used to make complex shapes such a star wheel.

I once designed a power supply for this operation, mine was a small lab supply of 100 amps.

The real supplies in the machine shop had larger supplies, 30,000 amps and the ability to turn off in a micro second or less. The turn off time was needed to stop arcing which would destroy the very expensive tool. This was with 1960 devices. Basically they used a bank of scr's to crowbar the supply to stop the arc very fast and then turned off the rest of the supply before it went up in smoke.
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Old Jun 25, 2014, 09:07 PM
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Thanks for the replies.

Having a slightly lower kv rating is good news for me. I tend to follow the low head speed crowd whenever I fly my helis.
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