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• Aluminum Levitator
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  I built the levitator from your article with the following changes.
  
  To precisely control the voltage to the coil I used a 555 timer to send a 40msec operating pulse to an A.C. solid state relay rated at 25amps. Thus when the 555 timer was triggered it turned on the solid state relay sending a 40msec pulse of 120vac to the coil. The time was more then enough to send the ring up to the top. Using the relay also eliminated the problems with triggering the coil with too long a pulse and blowing the fuse. It also keeps the coil very cool.
  
  I also found that the 1 lb spool of #18awg magnet wire came wound on a plastic coil with an inside diameter of 3/4". Thus the 3/4" dia bar of CRS steel that I bought fit inside the hole perfectly. This along with the fact that the wire at the beginning of the coil stuck out enoungh so I was able to grab both ends of the coil and wire it into the circuit without having to rewind the coil around the bar. The inside of the spool also made a good insulator between the coil and the steel bar. OF course you have to ground everything properly and fuse the circuit.
  
  Thanks for a good article
  engineerxx

  Posted by ccnyeng on July 18, 2011 at 13:43:21 Pacific Time

• Flying rings
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  I built this device years ago, before getting a EE degree. As I understand it, the device is basically a transformer with an open secondary, until some non-magnetic material is placed in the magnetic field. That conductor then becomes a shorted turn, with a lot of current flowing in it. And, whoosh .. away it goes. Or it floats.
  The design shown can be improved by :
  * Removing the aluminum tube - it acts as another shorted turn, and weakening the available magnetic field from the iron core. It should also reduce the current drain considerably
  * Replace the solid core with a bunch of thin iron bars - like you find at a hardware or home center store. This breaks up the eddy current in the core and cuts down on the losses.(heat)
  
  Transformer action can be demonstrated by lowering a coil of wire over the core with a light bulb across the ends.
  
  Phillip Milks
  phillipmilks@netzero.com

  Posted by phillipmilks@netzero.com on November 04, 2010 at 12:27:54 Pacific Time

• Wire
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  Thought I'd share a site that appears to sell wire much cheaper than Mouser: http://www.bulkwire.com/wire-cable/magnet-wire.html
  
  (I say "appears" because I haven't bought any yet so maybe they tack on huge shipping costs.)

  Posted by DeegC on October 18, 2010 at 19:40:51 Pacific Time