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Re: [TheTeslaTurbineList] permanent magnet bearings

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  • Bernard Clay
    ... Actually, Post has a simpler arrangement. Instead of wound copper wire, he inserts a conducting cylinder, aluminum or copper, (see 152 on
    Message 1 of 5 , Nov 30, 1999
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      >
      >>
      >>>From: "Gordon McAndrew" <gordonm@...>
      >>>Reply-To: TheTeslaTurbineList@onelist.com
      >>>To: <TheTeslaTurbineList@onelist.com>
      >>>Subject: Re: [TheTeslaTurbineList] permanent magnet bearings
      >>>Date: Thu, 25 Nov 1999 17:50:10 -0800
      >>>
      >>>I hate to ask this but, how is the field useful in suspending something.
      >>>It appears to be just a straight bi-polar field across the gap in the
      >>>middle.
      >>>
      >>
      >>Immobile and by itself, it doesn't. Coils of copper wire wrapped around a
      >>non-conducting body are also disposed in the central gap. The short
      >>version
      >>is that when there is relative motion between the dipole Halbach array and
      >>the copper windings, EMF is induced in the windings resulting in a second
      >>magnetic field. These two fields then repel each other after a transition
      >>speed is reached. Suspension of the body in the gap follows. A type of
      >>high-speed ironless motor/generator also by R F Post is built around this
      >>design. Just the type electrical apparatus the Tesla turbine enthusiast
      >>may
      >>find useful.
      >>
      >>
      >>BC
      >>
      >

      Actually, Post has a simpler arrangement. Instead of wound copper wire, he
      inserts a conducting cylinder, aluminum or copper, (see 152 on
      halbach_bearing.gif attached) inside the array. Rotating either the cylinder
      or the magnet array at a critical speed causes these bodies to repel each
      other due to eddy currents.

      Here also is a drawing of a Halbach array with Litz wire in the gap. (See
      halbach_litz1.gif)

      Now, what makes a Halbach array unique? For one thing, the magnetic field
      is redirected to one side only. A typical non-Halbach magnetic array
      usually wastes half of the field, adding in fact to cost by way of magnetic
      shielding. In the case of a circular Halbach array, one can choose to limit
      the field to the outside or the inside of the circle. In the drawings, the
      flux is facing inward, concentrated inside the gap. This forms a dense,
      uniform magnetic field. Apparently, says one stat, Halbach arrays put out a
      field 42 times stronger than that of more conventional ironless magnet
      arrays of the same volume. Following the bars that compose the magnetic
      array clockwise, we see that the magnetic orientation between each
      successive segment rotates in a clockwise direction. If the rotation
      between successive segments were arramged in a counterclockwise direction,
      the flux lines would bunch on the outside face of the array. The gap would
      be nearly empty.

      Post's team uses this fact to good effect in one bearing. This consists in
      two cylindrical Halbach arrays, one inside the other. The outer cylinder
      has a magnetic field that projects inward to its inner surface and the inner
      cylinder has a field that projects outward along its outer surface. Between
      cylinders is either wound copper wire or a one-piece non-magnetic cylinder.


      BC
    • Bernard Clay
      ... Richard F. Post currently does R&D work at Lawrence Livermore National Lab. Did a search at the lab s website (www.llnl.gov). R F Post s phone no. is
      Message 2 of 5 , Dec 1, 1999
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        >From: "Sam Garza" <sgarza@...>
        >Reply-To: TheTeslaTurbineList@onelist.com
        >To: <TheTeslaTurbineList@onelist.com>
        >Subject: Re: [TheTeslaTurbineList] permanent magnet bearings
        >Date: Wed, 1 Dec 1999 09:12:16 -0500
        >
        >Bernard,
        >How do I get in contact with R. F. Post I would like to pursue this to see
        >how it compares with Tesla's Dynamo.
        >Sam Garza

        Richard F. Post currently does R&D work at Lawrence Livermore National Lab.
        Did a search at the lab's website (www.llnl.gov). R F Post's phone no. is
        listed as 925-422-9853; his fax is 925-423-7914. Email address:
        post3@...

        Try the LLNL library which has documents online. On the search form on the
        'author' field enter 'Post R*' There are docs there on his work
        on the Inductrack, passive permanent magnet bearings, the Halbach array
        motor/generator, and his flywheel energy storage module or electromechanical
        battery as he prefers to call it. These are all in Adobe Acrobat PDF
        format, by the way.

        Happy hunting.


        BC
      • Paul Eitson
        Bernard Clay, Thanks for the posts of the diagrams .I am certainly more well informed. Time has not permitted my discussion of this subject. My son s flywheel
        Message 3 of 5 , Dec 2, 1999
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          Bernard Clay,
          Thanks for the posts of the diagrams .I am certainly more well
          informed. Time has not permitted my discussion of this subject. My son's
          flywheel disk generator design may benefit as a result. He is debating
          between a stationary or a rotating armature. I have given him copies of
          the diagrams to possibly include the arrays in his plans. Plans for the
          generator have not been formalized so suggestions would be welcome.

          Paul

          Sam Garza,
          Hope to hear how the dynamo comparison works out.

          Bernard Clay wrote:
          >
          > From: "Bernard Clay" <bernclay@...>
          >
          > >From: "Sam Garza" <sgarza@...>
          > >Reply-To: TheTeslaTurbineList@onelist.com
          > >To: <TheTeslaTurbineList@onelist.com>
          > >Subject: Re: [TheTeslaTurbineList] permanent magnet bearings
          > >Date: Wed, 1 Dec 1999 09:12:16 -0500
          > >
          > >Bernard,
          > >How do I get in contact with R. F. Post I would like to pursue this to see
          > >how it compares with Tesla's Dynamo.
          > >Sam Garza
          >
          > Richard F. Post currently does R&D work at Lawrence Livermore National Lab.
          > Did a search at the lab's website (www.llnl.gov). R F Post's phone no. is
          > listed as 925-422-9853; his fax is 925-423-7914. Email address:
          > post3@...
          >
          > Try the LLNL library which has documents online. On the search form on the
          > 'author' field enter 'Post R*' There are docs there on his work
          > on the Inductrack, passive permanent magnet bearings, the Halbach array
          > motor/generator, and his flywheel energy storage module or electromechanical
          > battery as he prefers to call it. These are all in Adobe Acrobat PDF
          > format, by the way.
          >
          > Happy hunting.
          >
          > BC
          >
          > > part of the "TheTeslaTurbineList"...from
          > the :"Tesla Technolgy, Today!" group
        • Bernard Clay
          ... How does a Halbach machine compare with Tesla s dynamo? I m not sure the question s fair. It s like matching apples and oranges. Tesla s dynamo is
          Message 4 of 5 , Dec 5, 1999
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            >From: Paul Eitson <xyme2@...>
            >Subject: Re: [TheTeslaTurbineList] permanent magnet bearings
            >Date: Thu, 02 Dec 1999 17:41:02 -0600
            >

            >Sam Garza,
            > Hope to hear how the dynamo comparison works out.
            >
            >Bernard Clay wrote:
            > >
            > > From: "Bernard Clay" <bernclay@...>
            > >
            > > >From: "Sam Garza" <sgarza@...>
            > > >Subject: Re: [TheTeslaTurbineList] permanent magnet bearings
            > > >Date: Wed, 1 Dec 1999 09:12:16 -0500
            > > >
            > > >Bernard,
            > > >How do I get in contact with R. F. Post I would like to pursue this to
            >see
            > > >how it compares with Tesla's Dynamo.
            > > >Sam Garza
            > >


            How does a Halbach machine compare with Tesla's dynamo?
            I'm not sure the question's fair. It's like matching apples and oranges.
            Tesla's dynamo is basically a high-current. low-voltage producer. Since
            Post uses litz wire for his preferred design, his Halbach array generators
            would be be high-voltage, low-current producers.

            The better question is if we replace the conventional magnets in a disk
            dynamo with Post's Halbach arrays, what sort of output would be realized?
            Would the power be significantly greater? Would voltage be higher? How
            about amperage? Someone could ask Post this. If not Post, then Merritt or
            his other co-inventors at LLNL.

            The Tesla disk dynamo descended from Faraday's. Now, how much power a
            Faraday disk puts out depends on just two things: strength of the
            intercepted magnetic field and the relative speed of disc rotor to the
            external circuit (the slip rings, the brushes) 'stator.' Neither speed or
            direction of the magnets seems to play any role on output. So there's not
            much point in spinning the magnets. In a practical machine, it's the
            conducting disk that's always spun. A problem of the Faraday disk was
            maintaining constant electrical contact between the collecting brushes and
            the disk given its high speed rotation. It was this problem that Tesla
            sought to resolve. And the clever arrangement we see in his disk dynamo was
            the result. The use of two copper disks allowed for higher voltages and use
            of opposite directions of magnetism for each disk allowed both terminals to
            be fixed to the shafts of both disks, bypassing the charge collection
            difficulty from the disk rims.

            Suppose we build a disk dynamo designed around a planar Halbach array (see
            planar_halbach.jpg). It will resemble a Faraday-type machine in looks only
            but will not be hobbled by its limitations. You can spin either the magnet
            array or the disk and still produce current on the disk. This choice wasn't
            possible with Faraday. In fact, in their litz-wire conductor Halbach
            electric generator, Merritt and Post preferred to spin the array and let
            the conductor be the stator, thus simplifying the extraction of power
            output. So, similarly, a Halbach array disk dynamo can avoid spinning the
            disk altogether and have the magnet array act as rotor instead. You can
            have a series of planar Halbach array rotors interleaved with stator copper
            disks strung on the same shaft to boost voltage.

            Neither Post or Merritt report exploring this configuration for use
            expressly as a power generator. They do suggest a similar design for use as
            passive bearings. We can only guess what other advantages such a dynamo
            would have.


            BC
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