# Magnet for non-ferrous metals...



## Sigman (May 1, 2003)

WOW...a fellow at work demonstrated his AC magnet for non-ferrous metals to me at work today. He made me take a 1" square of aluminum, test it with a conventional magnet (of course I knew it wouldn't pick it up) to make sure "no tricks" were involved.

He sets up his AC magnet, places the aluminum under the suspended magnet, plugs it in and....whoooosh the plate is transported up to the magnet. AMAZING...then he explained it to me. I love science & electricity...must have been in a closet for all these years or didn't read enough Popular Sciences!

Just do a Google search for AC magnet and you'll run across it...not a new item, though I'd never seen one before. Though not explained well in theory (I'm sure there are more detailed explanations in webland...), here's a site that explains how to build one.


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## JSWrightOC (May 1, 2003)

Induction motors and some maglev train designs rely on this principle. /ubbthreads/images/graemlins/smile.gif

I tried something once...I had an aluminum disc spinning on a drive motor, and helt a rare earth permanent magnet near it. The motor slowed down from the electromagnetic "drag" caused by eddy currents in the aluminum reacting with the magnetic field of the permanent magnet. I could actually feel the pull while holding the magnet. After stopping the motor, the disc actually felt mildly warm to the touch!


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## shankus (May 1, 2003)

Wow. I must say, I'd need to see it to believe it. 

I have a use for this already. I don't know how many times I've needed a magnet to pick up aluminum washers droped in the cockpit, or other equally hard-to-get-at areas.
I assume this thing will attract brass as well? Cockpit instuments are mounted with brass screws, and if you drop one, well, good luck getting it.

As long as the field isn't strong enough to damage aircraft equipment (which I doubt), it could be used for that.


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## Wits' End (May 1, 2003)

We butchered a cow yesterday??? I know what does that have to do with magnets, just wait. Cows are quite often given a magnet, by mouth, it will stay in their stomach (one of four) and catch misc. ferous metal that if it traveled further could cause punctures and death (called hardware disease).
So my son in getting rid of the offal found that magnet (I won't go into details here). It is strong. He was testing it's lift capability on different items. My Arc AAA was on a lanyard around my neck and he went to check it, before I could tell him "it's aluminium it won't work" the magnet sucked the Arc right to it. /ubbthreads/images/graemlins/confused.gif I did it again. Maybe I have a rare steel Arc AAA /ubbthreads/images/graemlins/ooo.gif . Nope I took the battery out and the Arc wouldn't budge. So the battery was being attracted not the Al Arc. But I was excited there for a minute and wondered how I could work it into a thread here. Thanks Sigman for this thread good timing /ubbthreads/images/graemlins/smile.gif


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## logicnerd411 (May 1, 2003)

Funny, I just ordered some NdFeB (Neodymium - Iron - Boron)magnets the other day and they are STRONG. Go here to learn more about them: http://www.rare-earth-magnets.com/ 

I've cracked many of them after they went WHOOSH towards each other. And my hand looks like a red appendage after all the pinching the magnets have done to me /ubbthreads/images/graemlins/ohgeez.gif

Dan


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## Quickbeam (May 1, 2003)

You can find some great rare earth type magnets in discarded hard drives. Pop them open and check around the armature - I have a pair here that I can barely pull apart. If you store them attached to one another the magnetic field is almost completely dampened. Apart they'll mess up your monitor from a foot away.


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## whiskypapa3 (May 1, 2003)

Aluminum motor rotor? Go watch your electric meter. You can remotely control it's speed by turning on various appliances.


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## James S (May 1, 2003)

Older car speometers worked this way too. An aluminum disk attached to a spring and a magnet attached to the cable from the engine as the magnet spun it pulled the al disk along with it harder and harder against the spring thereby moving the dial. It doesn't have to be AC, just a moving field.


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## Wylie (May 1, 2003)

Floating tops anyone?


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## LED_ASAP (May 1, 2003)

[ QUOTE ]
*Wits' End said:*
He was testing it's lift capability on different items. My Arc AAA was on a lanyard around my neck and he went to check it, before I could tell him "it's aluminium it won't work" the magnet sucked the Arc right to it. /ubbthreads/images/graemlins/confused.gif I did it again. Maybe I have a rare steel Arc AAA /ubbthreads/images/graemlins/ooo.gif . 

[/ QUOTE ]

All "boosting" flashlights should have an inductor inside which is ferric, if the magnet is strong enough, it should pick up that little ferrite core /ubbthreads/images/graemlins/smile.gif


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## LEDmodMan (May 2, 2003)

Those hard drive magnets are typically the Neodymium - Iron - Boron ones logicnerd speaks of. I have a couple of different sizes of these that are used in small consumer wind turbines to generate electricity. The smaller ones are roughly 1/2" x 2" x 1/4" and have a nice counter-sunk screw hole through it in the 1/4" direction. Add a drawer knob of your choice and these make great refrigerator magnets that can hold a small (1" thick) phonebook to the fridge!!! /ubbthreads/images/graemlins/ooo.gif /ubbthreads/images/graemlins/eek.gif 

The larger ones are almost double the size of the small ones (in all dimensions), /ubbthreads/images/graemlins/eek.gif /ubbthreads/images/graemlins/eek.gif but don't have a hole through them. /ubbthreads/images/graemlins/frown.gif These things (the smaller ones) are so strong, you can put one on each side of your forearm (near the elbow), and they'll stay there holding each other (and my forearm is NOT small!). These super strong magnets have many uses. I may have some to sell...


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## PsycoBob[Q2] (May 4, 2003)

If I can remember the link, there's a guy who sells 2" circular NdFeB magnets, and 2" square versions, too. used for magic tricks like balancing a nail on it's head... a foot away from the hidden magnet. I think he sells them on eBay, too.


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## Floating Spots (May 4, 2003)

[ QUOTE ]
*PsycoBob[Q2] said:*
If I can remember the link, there's a guy who sells 2" circular NdFeB magnets, and 2" square versions, too. used for magic tricks like balancing a nail on it's head... a foot away from the hidden magnet. I think he sells them on eBay, too. 

[/ QUOTE ]

I have two of them. The first time they got away from me, I thought I lost a finger. Those SNAP together. The seller was sedona2. I don't know if he still sells them, though.

There is another company that sells larger rare earth magnets. However, you have to call them to discuss your application before they will even send you the waiver. I never had the interest to jump through hoops. However, if you are, here you go: http://www.wondermagnet.com/dev/magnet37.html


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## Floating Spots (May 4, 2003)

Actually, the monster in the last post is much thicker than the 2" ones I have. I wonder how much the thickness affects strength?


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## yclo (May 4, 2003)

If the thickness of the magnet is in line with its magnetic field, then the strength of the field will increase also.

And when they bite, it hurts like hell.


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## Canuke (May 4, 2003)

If you stack magnets "vertically" or in series, the magnetic field will gain volume, but not strength per se. Stack them side by side, or in "parallel", and the field will get denser. So, the former instance will mess up a monitor from great distances, while the latter will have short range but stick like a mofo to a refrigerator.

As for aluminum, it isn't ferromagnetic, but it IS paramagnetic, which involves a weak attraction.

The neat effect I noticed while experimenting with my neodymiums was that an aluminum token experienced a kind of electromagnetic "friction" in the field of these magnets. When both were at rest, no net attraction could be observed. However, the aluminum seemed to resist changes in the relative velocity between the two items; it tended to follow the magnet's movements, and when dropped onto the magnet, it would slow down and settle lightly, instead of just hitting it.

Similar experiments using cupronickel (75% copper, 25% nickel) and nonmetals showed no effects at all. I wish I knew why cupronickel looks exactly like 100% nickel but has the magnetic properties of 100% copper. Any metallurgists in here?


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