8 Hard drive magnets for PMG?
By JeroenH, Section Mechanical Posted on Fri Mar 04, 2005 at 02:12:38 PM MST
Possible?

I've openened up 4 hard drives and extracted 8 magnets. They are very strong. They look like this: http://www.otherpower.com/images/scimages/1840/magnets.jpg (In th picture they still have their metal backing, I've removed those) I've have two questions: How are these thing polarized? I can't figure it out from the way they attract/repel each other. Is it possible they have a dual (???) north pole? Is is possible to create a small PMG with these magnets? I'm not going for high power, just proof-of-concept. It should produce 12V and (hopefully) a few hunderd mA. Is it possible to build a DanB-style PMG with 8 magnets? I just want to play around a bit before buying magnets.

8 Hard drive magnets for PMG? | 8 comments (8 topical)

Re: 8 Hard drive magnets for PMG? (3.00 / 0) (#1) by wphfla on Fri Mar 04, 2005 at 07:35:22 AM MST

How did you get the metal back plates off?  I have harvested a few of these and cannot get them off?  For a proof-of-concept prototype, I believe they could be useful. wphfla

Re: 8 Hard drive magnets for PMG? (3.00 / 0) (#2) by JeroenH on Fri Mar 04, 2005 at 07:41:43 AM MST

I took a very sharp wood chisel, inserted it between the magnets and their backplates and gave it a little tap with a hammer. When I did that the magnet lifted a few mm and I could remove it. One thing: the nickelplating stuck to the backplating so the neo-material of the magnet is exposed. So for outdoor uses it should be coated with something like epoxy resin. [ Parent ]

Re: 8 Hard drive magnets for PMG? (3.00 / 0) (#4) by RatOmeter on Fri Mar 04, 2005 at 08:36:45 AM MST

It's much better to not pry or chisel them off.  Instead, grip the bracket flange with a pair of Vise-Grips(tm), then tap/beat the other bracket flange against a hard surface (concrete floor, for example) with increasing force until the magnet pops off.  If you weren't getting too wild with it, the mag will slap back to the bracket instead of flying across the room.  I've had a 100% success rate with this method (no magnets broken, none still stuck on). Don't heat them to try to soften the "glue"... you most likely demagnetize the magnet instead. [ Parent ]

Re: 8 Hard drive magnets for PMG? (3.00 / 0) (#3) by RatOmeter on Fri Mar 04, 2005 at 08:30:50 AM MST

They definitely have 2 poles per face.  I would suggest that cut them in half. Check here: http://reresource.org/Definitions/M/Magnet/Hard%20Drive%20Magnets/ Yes, it is possible to create a PMG with them, just not very practical.

Re: 8 Hard drive magnets for PMG? (3.00 / 0) (#5) by JeroenH on Fri Mar 04, 2005 at 08:57:08 AM MST

Thank you very much! This is good info. OK, so when I break all the magnets in two pieces I should end up with 16 magnets. What would be the best way to arrange them? All 16 on a single rotor? Or dual rotors with 8 magnets each? And how many coils in each situation? 8 or 16? [ Parent ]

Re: 8 Hard drive magnets for PMG? (3.00 / 0) (#6) by jimfrank on Fri Mar 04, 2005 at 10:15:52 AM MST

It's not necessary to break the magnets in two, really. They have a north pole facing up on one end, and a south on the other. You can arrange them in a rough circle with the poles alternating N/S/N/S... With eight magnets, you get sixteen poles, so sixteen coils will work pretty well. When I remove HD magnets from the backing plates, I clamp the backing plate in a vise or grab it with pliers, and bend it. The magnets break loose easily, and I've never lost one to breakage this way.

Re: 8 Hard drive magnets for PMG? (3.00 / 0) (#7) by wphfla on Fri Mar 04, 2005 at 10:41:34 AM MST

Sorry to steal your thread JeroenH.  Thank you for the information all. wphfla

Re: 8 Hard drive magnets for PMG? (3.00 / 0) (#8) by hiker on Fri Mar 04, 2005 at 01:44:26 PM MST

just mount the mags in a vise and grab the metal backing with vise grips--then bend the metal backing back--the mags will break lose without breaking.. if you want to break the mags in half--toss one in a vise and score the backside with a fine tooth hacksaw--then give a quick snap with a pair of plyers--works great for a clean break..heres a shot of a mill i made about a year and a half ago--should have made the coils bigger--had coat hangers for lams--put out 8v or more--oh well-it was a fun starter.............. WILD IN ALASKA

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