Hard Disk Platter Magnetic Levitation
This was just a quick 1/2hr experiment that I performed one weekend. It just consist of an ordinary Hard Disk Drive (IBM 40Mb!) from a computer that has had the top cover removed and the heads taken off and placed to one side. The hard disk spins up when power is applied and runs for about 90 seconds before it spins down from the error (no read head! dur). The power comes from an old pc power supply I've turned into a lab psu for various projects. The magnet is a thin neodyme (rare earth) magnet that came from the same hard drive (controls the read head). The idea came from Barry Hanson's site, that I stumbled across awhile ago.
The magnet has a tendancy to wobble as it hovers or be attracted to the centre spindle, so it's a little hard to control. Also if you use too heavier magnet or too strong flux magnet it will slow the platter down. The magnets that are used on the read head are just about right. I did try my super strong heavy neodyme's on it but the platter stopped and the magnet stuck to the spindle!
The drive platters are made from poished aluminium and are non-magnetic to begin with. When a magnet is suspended above a rotating platter, it induces eddy currents in the platter. These eddy current carry their own magnetic field. This field is in opposition to the permanent magnet (eg. North-North, South-South). The two fields repel one another and create a levitation effect.
Things to improve the height:
If your drive contains multiple platters you can remove them and reposition them all together at the top of the spindle. This creates a thick sheet of aluminium and should create a stronger opposition.
My drive only contained the single platter though as it is about 14 years old!
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© Oliver Hunt 2006-2008