00:00I recently made this 17 pound copper tube to experiment with Lenz's Law using this
00:05terrifyingly powerful neodymium magnet.
00:07It's fascinating to watch this magnet seemingly defy gravity while it floats to the bottom
00:12of the tube.
00:12This happens because as the magnet moves it creates electric currents in the copper, which
00:17in turn create magnetic fields that oppose the magnet's motion.
00:20This invisible resistance slows the fall, making it look like the magnet is defying
00:25gravity.
00:25What's even more fascinating is that when I place the magnet in the tube and spin it,
00:30the magnet stays suspended in the center.
00:32This got me thinking, will a spherical magnet float in the center of a copper sphere?
00:36Well in today's video we're going to find out, but first I need to make a copper sphere
00:40that we can actually see into.
00:44I wasn't sure how I was going to go about designing something like this until I noticed
00:48one of my dog's favorite toys.
00:50Here's what I designed.
00:51It's as close as I could get to a sphere while still being able to see the magnet through
00:56it.
00:56This shape is actually called a truncated icosahedron, but that's a mouthful so for my sanity, I'll
01:02just refer to it as a sphere.
01:04I started by 3D printing it in PLA plastic.
01:08I'll use these 3D prints to make a mold out of ceramic shell.
01:20It came off the printer looking pretty good, but I still needed to spend some time cleaning
01:24it up to get it ready for casting.
01:26Next, I'll attach some sprues.
01:28These are what I'll pour the metal into and they're really large because they'll act
01:32as risers, supplying the castings with molten metal as they solidify and shrink.
01:41Here's the ceramic slurry that I use.
01:43Over the course of about a week I'll dip the models into the slurry a total of 9 times in
01:48order to build up a thick shell.
02:06In between each layer I'll cut them with fused silica sand.
02:10This helps thicken the shells and also adds some strength.
02:14Making complex shapes like these is where casting and ceramic shell really shines.
02:19There's no way I could make these any other way, and having a machine shop make them would
02:23be incredibly expensive.
02:27Next it's into the kiln to burn away the plastic and turn the shells into a strong ceramic.
02:34I don't just burn away all the plastic though.
02:36Once the temperature is high enough for it to liquefy I remove most of it, and then I return
02:40the shells to the kiln and fire them at about 1600 degrees Fahrenheit.
02:59Here's all the copper I'll be melting.
03:01This is 9 pounds or about 4 kilograms.
03:03It's mostly copper pipe with some wire thrown in there also.
03:07It'll take about an hour to melt this amount.
03:09Copper is always fun to melt because it creates these really cool looking green flames when
03:14I add fresh pieces to the crusool.
03:41Once the copper is hot enough to pour into the shells, I'll quickly remove the copper
03:44shells from the kiln while they're still extremely hot.
03:47Place them on some sand to catch any spills and then pour in the metal.
04:01It's always amazing to me that for all the prep work and time that I put into thinking
04:05about this, figuring out how to execute it properly without fumbling around or making any mistakes,
04:11it only takes a few seconds or so to cast these and they're done.
04:14It's out of my hands.
04:16I've done this hundreds of times by now, but I still get a little rush of adrenaline every
04:20time I pour a casting.
04:21I think that's mainly because of how much work has led up to this point and I just want
04:25everything to go right and fortunately most of the time it does.
04:46Now I just have to wait for them to completely cool overnight before I can start removing
04:50the shells.
04:57I'll have to use my sand blaster to carefully remove the shell because I can't risk trying
05:01to break it off since copper is so soft.
05:04I could end up deforming the castings in the process.
05:12This is actually really satisfying.
05:14Instead of just slowly blasting the whole thing away, I try to cut large pieces off.
05:23All right.
05:24Let's go.
06:14To give you some idea, each shell took about 30 minutes to remove.
06:24These castings turned out super nice looking.
06:27You can see these booger looking things here, which are caused by air bubbles as I dip the
06:32models into the slurry.
06:33These are really easy to remove with a chisel though, and besides that, they're just about
06:37perfect.
06:52Now I'm drilling a hole into the center while I have something to hold onto in the vise.
06:56It'll make it easier to file in the pentagonal shapes later on, and you'll see what I mean
07:01in a minute.
07:27It's not easy to pull through.
07:32And making sure, it's easier for me to open it.
07:35I wonder what I could use these for?
07:37Any ideas?
07:48It's really important that these pentagonal holes are filed straight and precise, as I'll
07:53be 3D printing plugs to fit perfectly into them.
07:56These plugs will serve as points where I'll be able to spin the sphere, so the fit needs
08:00to be exact for smooth and balanced rotation.
08:20The last step is to polish each facet, and this little belt grinder really made it easy.
08:26I'm using a Scotch-Brite-like belt, which can polish each facet in just a few seconds.
08:32Since it's solid copper though, it heats up really quickly, so I have to cool it down
08:36in between each one.
08:44Well here it is.
08:45I think this thing turned out incredibly cool looking.
08:48Honestly, even if I had just made it as something cool to look at, I'd still be really happy.
08:54Okay, let's find out if it actually works.
08:57Here are the plugs that I'll press into the holes I filed in.
09:00Hopefully they'll stay put.
09:07To hold the sphere together, I printed some clips, which should do the trick.
09:13The magnet I'm using is a 2-inch N52 neodymium magnet.
09:18It's the most powerful grade you can buy as far as I know.
09:24And of course, I also made a stand for everything to sit on.
09:31Okay, so I've resisted actually spinning this thing up until this moment, so hopefully something
09:37cool happens.
09:41Oh yeah, it is.
09:43It's actually floating right there.
09:45Look.
09:46There.
09:47And now it's kind of falling, but at the right speed.
09:51Right there.
09:53Yep.
09:55That's so cool.
09:56I wonder if I can get a better angle on this so you can see what I mean.
10:00Okay, so I changed up the lighting a little bit, and obviously it's a different angle,
10:03so hopefully you can see what I'm seeing.
10:07Yeah, it is actually floating there.
10:09It's just about getting the right speed.
10:13Right there.
10:15Yep.
10:16It's totally just floating there.
10:22That's awesome.
10:29Oh man, that's so cool.
10:31Let's try a drill.
10:32Let's try a drill.
10:58Let's try a drill.
11:06So I think when I do it really, really fast, centripetal force is just forcing it over
11:10to one side, I think.
11:12So obviously this is working, but it's difficult to get it at a consistent speed.
11:17And also this plug isn't fitting in there really well.
11:20I think it's kind of worked itself loose.
11:21So I'm going to need to reprint this, and then in the future maybe I'll hook it up to
11:26a motor, and that'll make it a lot more consistent.
11:32So clearly it works, but the effect isn't quite as dramatic as I was hoping for.
11:37There may be some ways I can improve on it, so let me know if you have any ideas.
11:42Besides levitating a magnet, there are a whole lot of other things I can do with this thing.
11:46By using another magnet about a foot away, I can rotate the whole sphere.
12:03It's really hard to show on camera just how strange it is to manipulate the magnet in here.
12:08It's almost like it's underwater.
12:10It's very bizarre.
12:13Let me know if you can think of some experiments I should try, and I'll make a compilation video.
12:31If you would like to follow along with the progress of my projects and help to support
12:35the channel, then consider joining my Patreon for Patreon-only content.
12:40I hope you enjoyed the video, and if you did, let me know what you think in the comments,
12:44give the video a thumbs up, and subscribe for future projects.
12:47Well, thanks for watching, and I'll see you in the next one.
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