Magnetic Levitation Sculpture

Now available for sale!

If you like it, but don't have the laser access or don't want to do the casting, follow the links at http://www.cadabralabs.com to get a kit.

The Idea:

In this instructable, we build a diamagnetic levitation sculpture, complete with easy adjustments for optimizing the levitation of the small cube magnet.  The instructions are fairly complex, and need a number of tools, but the end result is very nice!  See http://www.youtube.com/watch?v=W_hgNbEqVlE for a video of it in action!

How does it work?

We've all tried to get one magnet just the perfect height above the other so that the magnetic pull matches gravity, and the bottom magnet floats, but while this may be possible in theory, this would only work in a micrometer range of distances.  Even if you had something more steady than your hand holding it, any slight vibration would move it enough to move it out of that range.  So how do we do it here?

The bismuth we're using above and below the bottom magnet is diamagnetic.  This means it very weakly repels any magnetic force, but the stronger that force, the more it repels.  When you get the lifter magnet far enough away that its just barely far enough away from the cube magnet to lift it, the bismuth pushes it down until the cube is far enough away from the bismuth to be affected by it.  At that point, the bismuth below is close enough to the cube magnet to push it back up slightly. All you need to get it floating is find the right balance of the distance between the two bismuth tubes, and the lifter magnet above!  Both of those are adjustable in this project!

Items required:

About 1 square foot of 1/8" MDF or baltic birch plywood.
Access to a laser cutter capable of cutting through 1/8" MDF or plywood; alternatively you could use a jigsaw if you're a very accurate jigsawer.
1/10th lb of bismuth.  You might find this sold as fishing weights or online.
Pan to melt bismuth.
Casting forms to cast the bismuth into nice round shapes.
Sandpaper to smooth out the casts. (Not necessary but recommended)
1 5/16th" elevator bolt.
1 5/16th" nut.
1 5/16th" locking nut
2 6-32x3/4" bolts
1 6-32x1.5" bolt
4 6-32" nuts
1 strong nib lifting magnet.
1 3/16th" strong nib floating magnet

Step 1: Step 1: Cast the Bismuth

Making the mold:

The mold you use can be made pretty easily with some tin foil. Simply find something with a hole half an inch across, and carefully push the tin foil into the hole, pressing around the inside of the hole to get it as smooth as possible. You can either leave it in the hole (it will get a bit hot) or gently pull it out. It should hold its shape fairly well.

Melting the bismuth:

Bismuth melts at a pretty low temperature, so you can actually melt it on your kitchen stove. Alternatively, you can use a propane torch, but that's overkill.

Casting:

Once the bismuth is melted, carefully pour it into your mold.  Before the bismuth solidifies, stick the 6/32x1.5" bolt halfway in as straight up as posible, being careful not to burn yourself.  It should only take a minute for it to cool down, but you can run water over it to speed up the cooling.  Once its cooled, carefully unscrew the bolt out, and repeat the process with a second mold.

Smoothing:

At this point your bismuth cast is going to look pretty rough.  Use some rough sandpaper to get the big imperfections removed, and then finer sandpaper to remove the smaller ones. With a bit of work, you can make it look really nice. The most important part is making the top (away from the bolt hole) smooth and flat.

Step 2: Cutting the Pattern

Laser cut the pattern:

If you have access to a laser cutter, this part is easy. Load the pdf in the your laser cutters app, and cut the pattern.  If you're going to try to jigsaw it, print the pattern, trace it out on your wood, and go at it!

Once you're done, you should have all the parts as shown.

Step 3: Assembly of the Structure

Bottom platforms:

Place the largest triangle on the table. This is platform 1.

Put one of the nuts on the 1.5" bolt and tighten it at the head. Its important this doesn't move so that the platform will raise/lower properly. Thread that bolt through the bottom of the the next smaller triangle, and spin another nut onto the bolt. The largest star shape should fit onto that nut next, followed by the next smaller triangle. This is the platform 2.

Insert the three smallest rectangles into the holes in the middle of platform 1, and the other end of those rectangles into the bottom of platform 2. You'll have to hold it together for now or it'll easily come apart.  You can see it assembled in the second picture.

Top platforms:

Thread one of the 3/4" bolts through the next smallest triangle, and tighten the nut on the other side. Screw one of the bismuth tubes onto the bolt. This is platform 3.

Thread the elevator bolt through the next smallest triangle, followed by the smaller star.  Screw the nut onto it, so that the smaller star is snugly around the nut. Then thread the bolt through the next smallest triangle, and finally tighten the locking nut at the end of the bolt. This is platform 4.

Insert the three larger rectangles into the holes in platform 3, and the other end of the rectangles in the holes in platform 4. You can see this assembled in the third picture.

Final assembly:

At this point, a friends extra hands would help, but if you're careful and patient, you can do it yourself. 

Take platforms 1 & 2, and slip the three legs into the appropriate holes in platform 1. Move to of the three legs towards the platforms, and adjust until they fit in snugly. If you hold those two legs a bit tightly, it will all stay in place. You can see this in the fourth picture.

Now take platforms 3 & 4, and fit them into the appropriate slots on the two upright legs.  You'll have to be careful not to loosen the legs too much getting them in, or the bottom platforms might get loose. You can see this in the fifth picture.

When platforms 3 & 4 are in place, you can bring the third leg up, and again fit the platforms into the appropriate slots. You can see this in the sixth picture.

Finally, take the two smallest triangles and clamp them together at the top of the structure. Use the last nut & bolt to keep those together.  The structure should now be quite steady!

Step 4: Levitate!

That's it!

You can now play with your new levitation stucture. Just put the large magnet on top of the elevator bolt on top, and the small magnet between the bismuth tubes at the bottom.  Raise the lower tube by turning the bottom star until there's a gap of a few mm between the magnet and the top tube. Then, either raise or lower the top magnet (depending on if the lower magnet is sitting on the bottom tube or pulled against the top one) until the cube starts levitating!

Play with it!

Try different lifter magnets (or combinations of them), and smaller magnets to see how much levitation you can achieve!