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PM alternatives
By Warrior, Section Homebrewed Electricity Posted on Tue Sep 23, 2003 at 08:14:39 AM MST
PM alternatives

I'm very anxious to build a battery charging wind turbine. I have a shop full of machinery just waiting for the next project. The most efficient alternators seem to be the Neo Magnet type made from a brake drum and disc. My problem being that I am in Argentina and neo magnets have a prohibitive cost if you find any (I doubt it). The best I can find are speaker magnets, which I think aren't suitable because of their pole's orientation. I've also considered rewinding an induccion motor with 36 or so poles. I've seen people parallel capacitors arcoss the windings and they generate pretty good power above their normal running speed. In this case above 166 rpm with 36 poles. What can I do? Any suggestions will be appreciated.

PM alternatives | 9 comments (9 topical)

Re: PM alternatives (none / 0) (#1)
by Jerry on Tue Sep 23, 2003 at 10:44:55 AM MST

Speaker magnets will work fine. They are polerized just like a neo disc magnet. N on one flat side and S on the other the only diferance is there is a hole in the middle and they are very week by compairson but they are very cheap by compairson also. And there are lots of junk speakers around or mirowaves. Good luck. JK TAS Jerry

Airheads Page

Just how do I... (none / 0) (#2)
by TomW on Tue Sep 23, 2003 at 12:57:52 PM MST

Jerry;

I have some magnets from some old Jensen home speakers and while it is easy to get the magnet assembly off the speaker itself I cannot see how to separate the magnet from the metal parts the voice coil moves in and out of.

Any tips or tricks on how?

Thanks a bunch

Cheers.

TomW

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it

[ Parent ]

Re: Just how do I... (none / 0) (#3)
by John on Tue Sep 23, 2003 at 02:37:58 PM MST

Yes, You can secure the metal backing in a vice and heat the metal with a blowtorch, I use a propane torch, while applying side pressure to the magnet. Try to heat the metal evenly by moving flame around. If the magnets are Neodymium try heating by putting into boiling water instead of using a torch.

This should work for you, it has for me.

John

[ Parent ]

Re: Just how do I... (none / 0) (#4)
by TomW on Tue Sep 23, 2003 at 02:54:17 PM MST

John;

Thanks but if it was that easy it would be done already. These have what appears to be a magnet sandwiched between 2 metal plates with a round piece thats part of one plate going through the magnet and other plate. the voice coil moves between the outside diameter of the "rod" and the through hole in the second plate and the magnet. There is no way to slide anything sideways that I can see.

Thanks anyway.

Cheers.

TomW

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it

[ Parent ]

Re: Just how do I... (none / 0) (#5)
by windstuffnow on Tue Sep 23, 2003 at 06:49:25 PM MST

Tom,
I've used a knife and a hammer. Use a knife you don't really care to much about and stick the sharp edge down on the magnet and tap it under the steel with a hammer. Sometimes they will pop right off and other times you may have to go around the edge until she pops. Be patient with it, refrain from the 25 lb hammer use choice words instead of force...

Gosh this is fun...

Ed

Have Fun! Windstuff Ed
[ Parent ]

Re: Just how do I... (none / 0) (#7)
by John on Wed Sep 24, 2003 at 03:52:01 AM MST

Ok, it will be a two step process. First secure the magnet or one of the plates and apply heat to the other plate while applying side pressure. When the glue softens enough the plate should move a little. It should break loose with a sudden pop or jolt, depending on how much heat/pressure you use, but it won't move very far because of the center piece. Then you can pry it off. Repeat the process for the second plate. You could also try prying, just be carefull not to pry too hard before the glue is softened enough.

John

[ Parent ]

Re: PM alternatives (none / 0) (#6)
by wooferhound on Wed Sep 24, 2003 at 12:19:45 AM MST

I have been working with speakers all of my life, I have tried multiple times to remove the magnets from the steel backings, and have never had any luck. I never wanted to use heat on the already weak magnets. They always ended up cracked in half or some large chunk chipped off making the magnet unuasable for other purpuses. The speakers that I was working on were rather large at 10", 12" and 15", never tried an 18" or smaller than a 10".

I think speakers are really efficent as built, after all they are a coil of wire in a tight magnetic airgap, simular to a dual rotor design. it only takes a 1/4" or 1/2" motion on a 15 inch speaker in order to get 12vac out. In fact, if you hook two 15" speakers together with wire, then push on one of the speaker cones, the cone on the other speaker will move almost the same amount.

I have often thought about using a large speaker in a loud envirenment and rectifying the output to batteries.

-- W o o f

Re: PM alternatives (none / 0) (#8)
by Jerry on Wed Sep 24, 2003 at 08:21:52 PM MST

Hi Woof. Well that explains you handle (Woof). I've been an electronic and audio hobbiest since 1958. As I tell the story My uncle gave me an old Crosley radio and I ain't been right since. Got My first stereo job 1975. I've had 38 years of speaker collecting. I just put the speaker baskit in the vice and use a sharp chizel to pop the plate off. Sometime everthing breakes but most the time they come off good. I don't like the heat thing either. JK TAS Jerry

Airheads Page

[ Parent ]

Re: PM alternatives (none / 0) (#9)
by wooferhound on Wed Sep 24, 2003 at 11:54:14 PM MST

Yeah , I have a Crosley radio right here in the living room. It's just for looks and does not work. I have a sound and lighting company named "Woofer Hound" sound lighting and audio conversion (like cassette to CD).

http://wooferhound.com

-- W o o f
[ Parent ]

PM alternatives | 9 comments (9 topical)

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