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? How to cast a ferrite core

Discussion in 'Electronic Basics' started by Gary Atkins, May 22, 2004.

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  1. Gary Atkins

    Gary Atkins Guest

    We (son at school and dad) are playing round with a simple generator with 8
    air coils on a static disk and 8 neo. magnets on a spinning disk.
    Now, to get more power, it would be nice to make some sort of ferrite slurry
    and pour it into the air gaps to make solid cores.
    Has anyone tried this, or have any ideas?
    I was thinking of iron filings mixed with epoxy glue. I have not seen any
    suppliers of ferro-magnetic material in powder form.
    ps I did not intend the corny pun on line one.
  2. Long ago, I tried making ferrite toroids by mixing ferrite powder of
    various grain sizes with epoxy. At a consistency of damp sand, I
    achieved a permeability of about 10, though my ferrite was not a
    particularly high permeability type. So you might well get some
    improvement in your generator by this route. Keep in mind that your
    goal is to increase the permeability of the entire magnetic path from
    one permanent magnet pole, through the coil window, and back to the
    other permanent magnet pole, without giving the flux any better path
    to go around the coil.

    Are your coils and magnets mounted on iron disks or nonmagnetic
  3. Gary Atkins

    Gary Atkins Guest

    The coils and disks are mounted on thin mdf wood, but we might try perspex
    as well
  4. I remember reading a website almost two years ago. It had construction details
    on a wind generator. They made ferrite cores for the coils using ferrous
    material gathered from gravel roads/driveways/sandy beaches/whatever. They took
    large powerful magnets, covered in plastic I believe and drug them around on
    said surfaces to get the material needed. Then blended it with epoxy.

  5. Then there is little point in casting the holes in the coils with a
    ferrite mixture till you poke holes through the backing board
    (including behind the magnets) and cast a ring of ferrite behind both
    magnets and coils as well. Otherwise you have not made the total
    magnetic path around the magnets (from one pole to the other, through
    the coil) much lower reluctance then it is, now.

    You are beginning to find out why practical generators have all those
    precisely punched and stacked iron laminations. Their only air gap in
    the flux path is the one that allows the relative motion between the
    rotating and stationary parts.
  6. Ah! Space dust! A lot of that stuff is burned up meteorite dust that
    fell from space. Of course, these days, a significant part of it can be
    from scrap steel...


    Sir Charles W. Shults III
  7. I can't tell if you're being sarcastic or serious, or if this method would even
    work. Would it work? I'm really not all that in the know when it comes to
    these things. I just thought I'd mention it because it seemed plausable. I
    would imagine that there is lots of ferrous material in gravel dug up from
    quarries etc.. No? And, doesn't that material get created by forces inside the

  8. With millions of iron vehicles and other man made devices rusting all
    over the populated world, I think much of the magnetic bits in soil
    are from man made sources. But iron is also a very common element in
    the Earth's crust, and many iron bearing minerals are also
    ferromagnetic, to some extent. The big questions are what exactly are
    you going to gather by this method at any particular location, and
    what are its magnetic properties?

    Simply grinding on a piece of cast iron with a low speed abrasive
    wheel (to reduce burning) and separating the magnetic particles from
    the grit by this method would probably produce much higher quality
    core filling. Not ferrite, but something capable of handling
    considerable flux.
  9. cpemma

    cpemma Guest

    One of the naturally-occuring oxides of iron is magnetic, appropriately
    enough called magnetite:

    "Magnetite is a member of the spinel group which has the standard formula
    A(B)2O4. The A and B represent usually different metal ions that occupy
    specific sites in the crystal structure. In the case of magnetite, Fe3O4,
    the A metal is Fe +2 and the B metal is Fe +3; two different metal ions in
    two specific sites. This arrangement causes a transfer of electrons between
    the different irons in a structured path or vector. This electric vector
    generates the magnetic field."

    Slag from steel-making , sometimes used crushed for road-making, contains a
    modest amount of iron oxides, but I doubt the permeabilty would match the
    metallic form.

    OK, that's more than you needed to know ;-)
  10. ~^Johnny^~

    ~^Johnny^~ Guest

    I should think they'd fair right...
    wide-open at throttle dot info

    "The first step in intelligent tinkering is to
    save all the parts." - Aldo Leopold
  11. I dunno about where you're at but here the heavier stuff gathers in the
    eddies in streams, and can be picked up while panning for gold. Seems
    like any magnet dragged thru dirt will pick up a substantial amount of
    these iron particles.
  12. Rich Grise

    Rich Grise Guest

    I work at a weld shop. You could probably pick up a pound of the stuff
    dragging a magnet around the floor. Heck, I can drop a magnet on the
    rug and pick the stuff up. But a lot'd be oxide(s), because it's slag.
    But, who knows? Maybe the slag would improve something - I clearly
    know less than nothing about ferrite! :)

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