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Stacking Magnets
By billymc, Section Mechanical Posted on Wed May 11, 2005 at 12:40:25 AM MST
Magnet stacking??

I've searched the board a couple of times and haven't found anything about stacking magnets. Would stacking two disk magnets improve the strength of the poles (or flux or magnetism or whatever)? Bought the 100 lot of 3/8 x 1/8 disks and mounted a disk in each finger of a rewound auto alt. Not impressive results. Just wondering if it would be worth trying to drill deeper and stack two mags in the holes. I could probably fit up to a 1/2" diameter mag if stacking the 3/8 mags doesn't help.
PS: To get two 3/8 x 1/8 mags in a finger of the alt, the hole would be drilled all the way through. Therefore, no metal behind the mag!

Stacking Magnets | 12 comments (12 topical)

Re: Stacking Magnets (3.00 / 0) (#1)
by nvmike on Tue May 10, 2005 at 07:44:27 PM MST

I pressed of the rotor, removed coil and replaced with three microwave circular magnets, and replaced the rotor fingers, a few volts, turning by hand, not data yet. You could also stack you smaller magnets in between the rotors.

Re: Stacking Magnets (3.00 / 0) (#2)
by billymc on Tue May 10, 2005 at 08:21:38 PM MST

I did this to. More disappointing results. Still have a rotor with the 'speaker' magnets in it. Read a post about it and even with a good neo ring mag you wouldn't get much flux power at the fingers. Think it was a post or comment by Ed@windstuff.

[ Parent ]

Re: Stacking Magnets (3.00 / 0) (#3)
by RP on Tue May 10, 2005 at 08:43:05 PM MST

If you drill into the fingers and "inset" the magnets, the field shorts out through the steel around the sides of the magnet.. The magnets must sit above the steel, not in it.

[ Parent ]

Re: Stacking Magnets (3.00 / 0) (#5)
by billymc on Tue May 10, 2005 at 08:56:46 PM MST

hmmm, is this why zubbly is using aluminum sleeve to put mags in on his motor mods?

[ Parent ]

Re: Stacking Magnets (3.00 / 0) (#6)
by nothing to lose on Tue May 10, 2005 at 11:18:22 PM MST

Yes I think so.
Aluminum does not conduct flux the way steel does. He still has the steel under the mags though to conduct the flux where it is needed. If you drilled all the way through the fingers you would be getting the worst of both worlds, flux robbed/shorted by the steel at the sides and no steel under the mags where it is needed.
.
nothing to lose

Spelin and tpying are my strong points, not electronics.
[ Parent ]

Re: Stacking Magnets (3.00 / 0) (#4)
by nvmike on Tue May 10, 2005 at 08:43:36 PM MST

I may try another auto alt. feed 12 VDC to rotor, and tap off the ac and see what i get May get more than i am getting now, but would have to charge up 12 V bat. every so often depending on the amps going through rotor. Most say Auto alt. not worth messing with, but i like to experiment.

Re: Stacking Magnets (3.00 / 0) (#7)
by electrondady1 on Wed May 11, 2005 at 05:48:38 AM MST

i want to do this experiment , use a p.m. geni to power the rotor of an auto alt. perhaps the output of that unit could be used to power the rotor of a second auto alt. . the idea being ,to multiply the initial current several times in stages.no battery would be required. even a small pmg should be able to produce the 50 watts needed to excite the rotor of an auto alt.

[ Parent ]

Re: Stacking Magnets (3.00 / 0) (#8)
by electrondady1 on Wed May 11, 2005 at 06:01:38 AM MST

sorry, i got side tracked . as far as ive been able to discover stacking mags increases the flux but only by about 15% . one magnet of "x" thickness is more powerfull than a stack of mags of the same thickness.

[ Parent ]

Re: Stacking Magnets (3.00 / 0) (#9)
by ghurd on Wed May 11, 2005 at 08:20:46 AM MST

I was told 'around' 20%.
And I think it had to do with the type of magnet too.

Ghurd.info
[ Parent ]

Re: Stacking Magnets (3.00 / 0) (#10)
by nothing to lose on Wed May 11, 2005 at 09:57:28 AM MST

I think I heard that too, but they all equal something less when stacked than one magnet of the same thickness would as I recall.

Maybe 2 1/2" neos stacked have total 3/4 power of one 1" neo or somthing like that.
Not sure now but I think it was something like getting half the power from the second Neo??

So if stacking alot of thin Neos, would you keep adding half the power of one or would it keep falling till it made nearly no extra flux.

Kinda like if you wanted to fill a 1" space but only had 1/8" neos? Would 8 give you about a 1/2" neo power?
.
nothing to lose

Spelin and tpying are my strong points, not electronics.
[ Parent ]

Re: Stacking Magnets (3.00 / 0) (#11)
by nothing to lose on Wed May 11, 2005 at 10:38:44 AM MST

That might be a good idea, you have to gear it up anyway for higher speed so putting 2 motors on the same belt or chain should not be much problem. look how much junk is put on one car belt! Course you need the extra power from the blade set to run it all at once.

I had thought about maybe using several sets of blades to run one geared up motor faster and hopefully still have plenty of startup torque in low winds.

What I would like to eventually build is a wind gennie that looks like an airplane. Either twin engine or 4 engine. The problem I have is I don't want all that weight of motors way out on the wings like that, would have to add to much support and wings be too thick etc..

Supporting blades and preventing twist in the wings would not be much problem, perhaps belt/chain drive to a couple alternators mounted in the body at the tower would solve the problem. Each side would have 2 blade sets to spin them fast geared up for low speed blades, and a motor like a tread mill could provide the juice to excite them all?

For this idea, alternators are pretty light weight. If using 4 100 amp ones and getting 50 amps each that's 200 12V amps or 2400watts from one gennie and one tower. I would be happy with that, anything more would be great.

For controlls I think the rudder to guide it into the wind like the tail normally does. To furl I had a couple thoughts. Offset the weight of the gennie a bit forward, design in a little lift on the front wings but not much so only high winds have any effect and also use the tail wings to tip it up in high winds. I have seen gennies on here that used lift up furling before I think, instead of side turning. This would be the same tilt up idea.

Something I am thinking about, would like to do, but not working on! Would be happy to look at pictures of anyone elses if they build one like this :)

I think it could be a good but maybe complicated design that would have lots of bennfits.
.
nothing to lose

Spelin and tpying are my strong points, not electronics.
[ Parent ]

Re: Stacking Magnets (3.00 / 0) (#12)
by billymc on Wed May 11, 2005 at 10:51:21 AM MST

Thanks for the input. Time to come up with a new plan!

Stacking Magnets | 12 comments (12 topical)

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