While we wait for the world to reopen from the virus, I’ve had more free time than usual so I put together a project that had been on my list for a while.
We normally think of magnets sticking to metal, but magnets can also repel certain materials. This effect is called diamagnetism. The repelling effect is much weaker than the attracting affect to iron, almost to the point of being useless. You’ve probably seen this effect demonstrated with superconductors, but I don’t have access to superconductors and liquid nitrogen so that rules that one out for me.
One of the best diamagnetic materials at room temperature is pyrolytic graphite, which can be purchased relatively cheaply on ebay.
In order to make that graphite float, you need to have the magnets arranged with alternating poles in a checkerboard pattern. I made up a platform a while back using some magnets that I salvaged from an industrial servo motor, and it worked well but the magnets were fairly large and the platform perfectly flat so the graphite would always float to the edge. I wanted a platform that was concave so the graphite would return to the center when at rest.
I found a scrap satellite tv dish and cut out an 8.5 inch octagon from that to get the shape of the platform. (a steel base works best because the magnetism on the bottom of the platform can basically be redirected to the top making a stronger field on the top.) I polished all the paint off the top of the steel octagon and made a frame out of an oak 1x2 board.
The magnets I ordered on Aliexpress a few months ago. They finally arrived a couple days ago so I put everything together yesterday.
(This is my first attempt at posting images here. Hopefully it works.)
The project turned out decent, but the graphite doesn’t float as high as I had hoped. It floats roughly 1mm above the platform but I was hoping for closer to 2mm. Apparently the magnets I ordered on Aliexpress aren’t as strong as the magnets I salvaged from the servo motor. It took about 1600 magnets to fill out the entire area. The magnets I ordered didn’t have a strength rating listed so I’m assuming they’re N35. N45 or N52 would have been much better but prohibitively expensive.
It’s a fun toy, but probably not worth the money and effort it took to make.
Most excellent Pip! I love neo’s and have a closet full of them. The largest being a 6”X3” disc at n51. It is a dangerous hunk of metal that one. It fiddles with flat screens starting at about 10’ away and will wreck some watches and things like that. One year I gave away two small joined discs to some relatives for Xmas. The challenge was to get them apart bare handed. At a party one of my intoxicated cousins got them apart and went around showing everyone. When finished he put one in his left pocket and one in the right to keep them apart. That’s right, they came together on his boy parts and he’s desperately looking for help to get them off. The guys at the party will have nothing to do with this, but the women find the affair devilishly funny so they volunteer to help him out. They assessed the problem and agree on a solution. The ladies dropped his drawers, cut off his shirt tails and pant pockets and go to work. They took dull table knives and worked them under the magnets and finally got them off the poor guy without further hurting him. I no longer give neodymiums away. Flashlights, you bet.
Funny you mentioned that… I always wanted to somehow take an air hockey table, make it so there were channels that went through and allowed the use of moveable players like in a Chexx bubble game……but with a large air hockey field
I looked into it but they don’t stay in place as well and you get almost the same effect by using the steel behind the magnets. It basically completes the circuit on the back side so all the free field is on the top side. I did try it though. The magnets wouldn’t stay in place without glue.
It would be awesome but at $160 per square foot it would be prohibitively expensive. Also it doesn’t really act frictionless. Seems to slow down way quicker than you would expect. I assume the induction generates a field that counters the motion.
Or it could just be air resistance. My vacuum chamber is too small or I would find out.
LoL that guy isn't me, I swear! :-D Yet I have to admit that, for a moment, I found myself surprised when I saw him so lookalike. But I still have some hair on top of my head!
boy I do miss these diamagnetism science toys. They were super expensive in last decade and now thanks to online stores everything is cheap.
I could even buy one of these kits in Aliexpress haha.
