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Voodoo engineering

Discussion in 'Electronic Design' started by default, Nov 8, 2006.

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  1. default

    default Guest

    I was looking to tinker with some magnets and build a brushless motor
    and came across something unusual. It is a perpetual motion machine -
    and I can't see why it won't work. Can someone 'splain it?

    the simplified version: The idea is to take two magnets. One magnet
    is cylindrical and magnetized through its axis. The other is similar
    but the shape is not relevant.

    So you take the round magnet and put it on an incline and bring the
    other close so it repels the round one causing it to roll up and away
    from the second magnet. - no problem.

    The idea is to harness that reaction and turn it into a motor with no
    input power . . . To that end, the round magnet is put in a
    non-magnetic hamster cage sort of device so it just rests in the
    bottom of the cage. The cage axis and magnet axis are parallel to
    each other. Now the other magnet is brought to the outside of the
    cage and repulsion causes the round magnet to roll away from the
    outside magnet and up the side of the hamster cage. The weight of the
    round magnet disturbs the balance of the cage and gravity tries to
    pull it back by rotating the cage - which in turn tries to bring the
    rolling magnet closer to the repelling magnet - and supposedly this
    causes the cage to rotate.

    Can someone bust this myth for me?

    The link is

    The information is sparse and fractured - they seem to be talking
    about at least three entirely different types of zero input power
    magnetic motors, and three variations of the hamster cage motor - one
    with an internal to the cage repelling magnet, external to the cage,
    and outside the cage (so the rolling magnet is trying to climb from
    greater than 270 degrees towards zero resting on the outside of the
    hamster wheel) - but the basic principle stays the same - rolling
    magnet causes hamster cage to rotate.
  2. Tim Wescott

    Tim Wescott Guest

    * You do work raising the free magnet.
    * The free magnet does work on the magnet on the cage.
    * Congratulations! You have successfully transferred energy from
    your muscles to the cage!


    Tim Wescott
    Wescott Design Services

    Posting from Google? See

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at
  3. Tim Williams

    Tim Williams Guest

    Seems to be that, they expect the magnet inside to 1. be raised by the
    external magnets, thus 2. elevating it inside the circle, causing it to 3.
    fall, thus turning the wheel. The cycle is continuous, as the system is

    The most obvious fallacy is that magnetic attraction or repulsion in this
    direction is NOT angular (and if it were, it would be a conservative force
    corresponding to the dipole moment!), that is, it contributes no rotation.
    Tie a string from the center of gravity of the inside magnet to some point
    outside and you'll see it doesn't turn the wheel. You can turn the wheel
    and, due to gravity and tension, the inner weight will remain in the same
    position (and turn due to friction with the drum), but it won't just go and
    start spinning faster and faster. There is no difference between using a
    string and magnets, because you're only using magnets to hold it up without
    a string! No one will doubt that a string, rod and drum won't spin to
    infinity, but one knows how they work...there must be
    some wonderful mystical power at work here we can tap!!!!111 No, sorry,
    magnets ARE very well understood, and well understood to be unity or
    less-than-unity sorts of elements.

  4. default

    default Guest

    You do the "work" one time only, once the magnet is in position (and
    tied down) it will continue to repel the internal magnet.
  5. default

    default Guest

    The internal magnet, from my understanding, isn't raised off the
    inside circle. It just rolls away from the repelling magnet, in so
    doing rolls against and slightly up the incline presented by the
    hamster cage. Friction between the inside magnet and cage transfer
    the weight to the cage and upset its balance. Cage rolls to reach
    weight equilibrium and that rolling moves the inside magnet closer to
    the external one.
    The repulsion is not angular, but magnets will roll up an incline to
    get away from repelling magnets.

    (and if it were, it would be a conservative force
    You lost me with the string. For this to work as posited, the
    internal magnet must roll away from the external one - the external
    one is not directly below the internal magnet, and not lifting it, but
    on one side of the cage axis.

    I understand the fascination with magnets and their voodoo appeal.

    Logic suggests that if this really did work, there'd be tons of
    demonstrators and executive desk toys based on the principle - if not
    actual power sources - so therefore it must not work. This stuff was
    first posted in 1999 . . . plenty of time for capitalism to find a way
    to exploit it for profit. (like those so called "radiometer"
    demonstrators - white/black vanes on a pivot in a partial vacuum) So
    it must not work - I just don't see why it shouldn't.

    Many of the 'effects' of magnets are well understood. I'll buy that

    My interest was in seeing how little power I could use to physically
    move something. I was always fascinated by those advertising posters
    with the kinetic elements that were common in the 50's. Most of them
    used a D cell, magnet, coil and mechanical switch. They would keep an
    element of the poster working for months on the battery cell - and a D
    cell back then wouldn't have stood up to a AAA today. The "Bedini"
    motor seemed like a good place to start - so I'm looking at some
    weird/fringe ideas.
  6. Tim Wescott

    Tim Wescott Guest

    Right -- that means your motor can only run for one cycle. If you want
    multiple cycles and therefore continuous output, you'll need to keep
    working the free magnet.


    Tim Wescott
    Wescott Design Services

    Posting from Google? See

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at
  7. default

    default Guest

    I still don't see it. Repelling magnet causes inside magnet to roll
    up incline on inside of wheel - wheel is unbalanced and rotates to
    bring the repelled (inside) magnet closer to the repelling magnet,
    repelling magnet causes inside magnet to roll away (continuously)
  8. Rich Grise

    Rich Grise Guest

    Build one and it will become obvious to you why it won't work.

  9. Rich Grise

    Rich Grise Guest

    Just build a demo unit, and the world will beat a path to your door to
    find out how you did it.

    Good Luck!
  10. Macgyver

    Macgyver Guest


    you are seeing is a smoke and mirrors trick. You put energy in to
    start the cage turning, the cage eventually stops turning after a
    certain amount of revolutions. Remove magnets and try again using same
    input force to start cage turning. Hey, it turned more times <sigh>.

    The article in the link said it best......."The rpm on mine was slow
    maybe 50 rpm. It turned about 16 turns before the top magnet hung up on
    the side plate. I have not been able to get it to work that long

    Another case of lack of BASIC scientific and motor knowledge, as well
    as incomplete and/or piss-poor lab work and results. Nothing magic
    about it. Just plain wrong.
  11. Ok, simple explanation. First, you could try it, but what happens is
    that very quickly the system reaches equilibrum with the wheel slightly
    off balance by the amount the outside magnet is pushing the inside magnet.

    You see, the friction of the magnet on the wheel pushes the wheel BOTH
    ways, so for it to roll up, it has to counter that friction, so the
    equilibrum comes when that friction just matches the magnetic repulsion.

  12. default

    default Guest

    From what I read, the only energy input is to place the repelling
    magnet where it will influence the rolling magnet - no need to start
    turning the cage.
    I suspect that is where he takes the rolling magnet out of the cage
    and rests it on the outside of the cage, and places the repelling
    magnet below it.

    Like I mentioned, the writing leaves a lot to be desired. The
    author(s) reference to three different ideas one is supposed to
    already be familiar with (also involving perpetual motion.magnets) and
    three variations of this idea - repelling magnet outside the cage,
    repelling magnet inside the cage but fixed to the axle and not moving
    - but forcing the rolling magnet away and downward, and putting the
    rolling magnet outside the cage and trying to get it to climb the

    I think it is that last idea where he can't keep the magnets aligned
    and keep it turning. On the outside of the cage - the friction and
    rolling direction both work in favor of the cage turning.

    What should happen with the internal rolling magnet, is the magnet
    should roll away from the repelling magnet and part way up the
    opposite curve then stop - friction would prevent it from allowing the
    hamster cage to drop back to weight equilibrium - the magnet and that
    part of the cage would be pushed away from the repelling magnet

    That's where the ball bearings come in I suppose. Decouple the
    rolling magnet from the inside of the hamster cage.
  13. default

    default Guest

    Yeah, I see that now. That's the reason for the bearings on the ends
    of rolling magnet . . .

    He's got it covered too - put the rolling magnet on the outside of the
    cage so it is trying to roll up the cage surface. Rolling magnet and
    cage both turning in the same direction at their contact point.
  14. ehsjr

    ehsjr Guest

    If there is 0 friction, the rolling magnet reaches
    a point of equilibrium where gravity and magnetic
    repulsion are equal. The cage does not move, due
    to 0 friction. If there is friction, the rolling
    magnet moves away from the fixed magnet, taking the
    cage with it, bacause of friction. It reaches a point
    of equilibrium as before, and holds the cage there,
    due to friction. In either analysis, equilibrium
    will be reached and the motion will stop.

  15. Rich Grise

    Rich Grise Guest

    I'm still waiting to see the videos of the demonstration model.

  16. joseph2k

    joseph2k Guest

    There is no net force on the bar magnet or the hamster wheel. They just sit
    there in that position. Do your freshman Physics (free body diagram).
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