Newsgroups: sci.physics.electromag Path: columba.udac.uu.se!sunic!trane.uninett.no!eunet.no!EU.net!uunet!news.crd.ge.com!crd.ge.com!mallick From: mallick@crd.ge.com (John Mallick) Subject: Re: Free-floating magnet possible? Message-ID: Sender: mallick@proteus (John Mallick) Nntp-Posting-Host: proteus.crd.ge.com Reply-To: mallick@crd.ge.com Organization: GE Corp. Research And Development References: <2m7oeu$43l@agate.berkeley.edu> Date: Fri, 18 Mar 1994 13:37:25 GMT Lines: 101 In article , jad@harrierx.cdev.com (James A.Dahlberg 490TX) writes: |> In article roh@spot.Colorado.EDU (ROH JOHN J) writes: |> >In article <2m7oeu$43l@agate.berkeley.edu>, |> >Amnon Silverstein wrote: |> >> Question: Can an object be made to float with magnets in such a way that |> >> it is not touching anything? |> |> I read an article in Extraordinary Science, a publication of the |> International Tesla Society, about a method for doing this. The author of |> the article is Jeff Dunan, Advanced Scientific Applications, 1880 Dairy |> Ashford - suite 510, Houston, Texas 77077, ph:713-597-1111, fax |> 713-597-1115. The inventor is Andrew Alcon, and he calls his invention |> Electro-Dynamic Magnetic Levitation (EDML). The article is in the |> Oct/Nov/Dec 1993 issue. |> |> The inventer is patenting his method, and expects to get a patent early this |> year. His demonstration setup had 2 spinning conductors with a magnet |> floating above them, something like this: (parden the lousy circles) |> |> O <----------- this is supposed to be the magnet, |> /-----\ /-----\ cylindrical in shape |> | | | | |> | . | | . | <----- these are spinning conductors,actually |> | | | | cylindrical in shape |> \_____/ \_____/ |> |> I think the conductors have to spin in opposite directions, but I don't know |> for sure. And they have to spin FAST. For 2" diameter disks (cylinders), |> they have to turn 9000 RPMs. For 1" diameter disks, they have to turn at |> 17,000 to 18,000 RPMs. |> |> Here is a quote from the article on the underlying principles. |> |> "The technical explanation as to why I believe the magnet is being |> stabilized is that it is generating an electric current, an emf, in the |> aluminum disc and the return flux path of the magnet cuts through the disc |> parallel to its axis of rotation, therby simulating an opposite magnetic |> polarity on both sides of the disc, relative to the magnetic polarity of the |> levitated magnet. |> |> It is essential for the magnet to have its poles perpendicular to the |> relative motion between it and the conductor. We have been able to measure |> DC mA directly off of the discs when the magnet is being levitated above the |> discs. |> |> We believe that this induced emf is in some way interacting with the |> magnetic field of the magnet to keep it secured in its position. The |> stabilizing force is so strong that if you had four discs instead of two |> discs and if you had them positioned so that their axis of rotation was |> vertical to the plane, they would suspend the magnet in the center." |> |> End of quote. |> |> I think the magnet is of a special construction, actually being composed of |> several magnets like so: |> |> Well, I don't have time to draw it. But the magnet is built out of several |> pie shaped magnets arranged with their poles alternating like so: |> |> s N s |> N N |> s s |> N |> |> |> Potential applications envisioned by the inventer are maglev transportation, |> sensors, wind tunnel maglev. |> |> +------------------------------------------------------------------+ |> | Jim Dahlberg Computing Devices International | |> | jad@verdin.cdev.com A Division of Ceridian | |> | james.a.dahlberg@cdev.com | |> +------------------------------------------------------------------+ |> If you spin the conducting disks fast enough (so that the transit time of the is less than the magnetic diffusion time of the conductor), then the material will act like a "superconductor" in that it will tend to exclude the magnetic flux; this will generate a levitating force. Dick Thornton of MIT used an aluminum disk and a tethered rare-earth magnet to demonstrate the principles of electromagnetic levitation (for maglev) years ago. The counter-rotating cylinders just enable the inventor to create stabilizing field, since the magnet sits in the "trough" between the two cylinders. See "Electromechanical Dynamics Part II: Fields, Forces and Motion" by Woodson and Melcher if you want all the gory details. Nothing magic about this as far as I can see. Cheers, John -- .... .. .... .. .... .. .... .. .... .. .... .. John A. Mallick WA1HNL E-mail: mallick@crd.ge.com GE Corporate Research and Development Phone: (518)-387-7667 (W) Schenectady, NY 12301 FAX: (518)-387-6560 (W) .... .. .... .. .... .. .... .. .... .. .... .. "Work like hell. Tell everyone everything you know. Close a deal with a handshake. Have fun." --- "Doc" Edgerton