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Next: Appendix 1 Up: Spin stabilized magnetic levitation Previous: How it works

Materials to experiment with

Base magnets can be ring magnets or an array of barrel, bar, or disk magnets. Usable large (10 cm OD) ring magnets can be found on speakers or in microwave oven magnetrons. (It is not easy to remove ring magnets from speakers. Sometimes the glue will release in boiling water but not always.) If broken speakers or magnetrons are not available, 4 bar magnets arranged in a square with their north poles inward, or barrel magnets arranged in a square or circle with their north poles up can be used. These will have to be put on a steel plate or glued to prevent them from moving. A steel plate will also have the effect of increasing the field strength and allow the magnet positions to be adjusted. Rings with larger mean radius have a higher levitation point but a weaker field and gradient at the levitation point. Small ring magnets for the spinning top can be found at Radio Shack, 5 for less than $2 but they are weaker than the tops that come with the Levitron and require a stronger gradient to levitate. The capture volume is quite small and the weight of the top critical so quite a bit of fussing is usually required. The weight must be adjusted to within approximately 0.2 grams.

When weighted correctly the top does very little nodding around the well. The top can sometimes be straightened up by raising and lowering the lifter plate a few times below the levitation region. The lifter plate can also be used to damp out some of the vertical oscillation after the top has left the plate. If the base magnet is not uniformly magnetized, it will need to be tilted so that the field at the levitation region is level. Sometimes the magnetic moment of a homemade ring magnet top is not purely axial. A small transverse moment makes the top easier to drive (as in figure 4), but it also makes the top fall down sooner.


next up previous
Next: Appendix 1 Up: Spin stabilized magnetic levitation Previous: How it works