Some time ago I came across the principle of a Bismuth Levitator and of course I was immediately enthusiastic. Of course, I wanted to build my own levitator. As far as I know it is the only way to let an object levitate permanently without putting energy into it in form of electricity, cooling, etc.
Table of contents
Video
The following video shows the entire construction in fast forward, and the bismuth levitator "in operation":
General information
If you play with magnets, then you realize pretty fast that it is simply not possible to create a permanent state of levitation with permanent magnets. In 1842, Samuel Earnshaw proved that a static magnetic or electric field can't hold some objects in a stable equilibrium (→ see Earnshaw's theorem).
But how can we still bring a magnet to levitate?
- Firstly, we could realize that with an electronically controlled electromagnet.
- Secondly, we also can do that by using diamagnetic materials (→ see Diamagnetism).
Diamagnetic materials behave exactly the opposite principle to a para- or ferromagnetic material. It is repelled from the poles of a magnet. Unfortunately, the diamagnetic effect is so small that you hardly notice it. Bismuth or pyrolytic graphite have the most diamagnetic effects (with the exception of superconductors).
Basic construction
The basic construction must look as follows:
At the top there is a permanent magnet that attracts the lower magnet. Without the two bismuth plates the lower magnet would be attracted upwards or the magnet would fall down. Definitely the magnet wouldn't stay in a fixed position (as previously described). If you place the two bismuth plates according to the sketch, they stabilize the magnets because the magnet repels both plates. The optimal distances between the individual plates and magnets must be found by experiments. However, the distances between the lower magnet and the two bismuth plates must be relatively small, because it is very difficult to stabilize the magnet with high distances.
Construction drawings
Before you can start building, you have to think about the construction. In addition I have created the bismuth levitator in CAD.
Here you can download the construction drawings in PDF format: Bismuth levitator: construction drawings [German]
Working steps
Manufacturing of the bismuth plates
First, the purchased bismuth was heated in a metal bowl with a Bunsen burner. The result was this plate:
Then I milled with my CNC milling machine two small plates out of the large bismuth plate and then I grinded and polished them:
Manufacturing of the magnet holder
To vary the position of the upper magnet, I glued the neodymium magnet to a thread which is from a banana jack. The magnet has a holding force of 6.7 kg, a diameter of 15 mm and a height of 8 mm.
Milling of the wood / labeling of the bow
All other necessary parts were machined from a 18 mm thick wooden board and the bow was subsequently labeled with the CNC milling machine.
The following parts had to be milled:
- bottom plate
- bow
- bismuth holder
- knob
Here you can download the G-code for milling the bow in PDF format: G-Code: Bow [German]
Here you can download the G-code for labelling the bow in PDF format: G-Code: Bow label [German]
Here I have to mention that the first letter is milled several times with this G-code because I clicked too many times on the letter in the software but that doesn't matter.
Grinding of the wood / painting
In this step, the milled and labeled wooden parts were grinded with sandpaper and then painted with a dark wood stain (color: teak). On the following picture the wood isn't painted.
Assembly
First, the bismuth plates were pressed into the bottom plate and in the bismuth-holder and they were fixed with a little glue. Then I glued wooden dowels into the holes of the bottom plate.
Then the bow was glued to the bottom plate and the nut from the magnet holder was glued in the central hole of the bow with 2-component glue.
The final bismuth levitator
Finally, you can see the finished bismuth levitator:
