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Might This Work? A Diamagnetic Theory

  1. Jul 15, 2010 #1
    I was watching a Newton's Cradle swing back and forth and it made me think: Is there another way to do this? No strings attatched?

    I thought of several ways to do this, but my favorite was the magnetic concept. Using neodysium spheres, I thought I could propel a sphere forward once, then use a different magnet to propel the magnet back to me. I believed If a northern polarized sphere went towards a northern polarized magnet, then it would bounce back fast, maybe without even touching the magnet.

    Around this time I discovered that magnetic spheres are polarized so that "North" and "South" were on opposite ends. This would give the concept a fifty percent chane of working with each roll, and I wanted it to be full proof.

    Browsing around the internet, I heard about a special type of magnet, a diamagnet, would repel all other magnets, no matter the charge. I heard bismuth was the strongest of the above, so I am currently using it in the design.

    However, I do not want to build this contraption if it won't function at all. So I have put together a little test. So tell me:
    Is this possible? {note yellow is diamagnet, sphere is neodysium}
    If the sphere is gently pushed towards the bismuth, will it stop and reverse directions before hitting the bismuth itself?

    If not, do you have ideas? I am open to showing the concept to anyone who needs more description.

    Please help me in any way possible.

    All responses are appreciated.

    Thanks alot!



    "I'll need some glue, some string, and a heckuvalotta duct tape."
  2. jcsd
  3. Jul 15, 2010 #2
    I would say it's a theoretical possibility but not a practical one.

    Newton's cradle works because the system has almost zero loss, the spheres hold enough energy that the losses on impact and through air resistance are relatively insignificant.

    If you translate the mechanism into say balls rolling in a parabolic wooden channel, the friction losses would 'kill' the motion rapidly.

    Then, the diamagnetic effect is weak - very,very weak - unless you have a superconductor - and so it's unlikely to act well on a heavy sphere. But a light sphere won't hold enough kinetic energy for the motion to sustain for long against friction losses.

    All in all it's a loser. :smile:
  4. Jul 15, 2010 #3
    I just have a few questions for you to think about, and a couple guesses.

    In what ways would you like it to be "like" a Newtons Cradle? In that it "demonstrate the conservation of momentum and energy", as described in the wikipedia article? Or in what other ways, since you mention the possible lack of strings as well as using magnetic repulsion instead of contact? Is the rolling magnet really the hope, or just to demonstrate repulsion? Based on this quote from the wikipedia article on diamagnets: "Nevertheless, these values are orders of magnitudes smaller than the magnetism exhibited by paramagnets and ferromagnets", I think you should give up the thought of an interesting demonstration using any diamagnet. A thousand times less than a refrigerator magnet is not going to give you significant (visible?) acceleration. If you really want a Newtons cradle without strings (magnetically levitating?) then I think you better think again. On the other hand you might make an optimally curved inverted magnetic track for steel spheres to roll underneath, but rolling friction and the tendency of the spheres to themselves be magnetized and stick together are likely problems.

    If you just want to demonstrate magnetic repulsion I think you can do that (a couple doughnut magnets on a vertical dowel, perhaps?). The 'sproing' of two like poles of decent magnets can surely make a nice little project to play with when you can minimize or eliminate the friction from whatever you use to constrain them from just flipping and snapping together.

    It does seem you would do well to review magnetism, for example the nonexistence (at least in practice macroscopically) of magnetic monopoles.

    Hope these comments are of some help.

  5. Jul 15, 2010 #4
    OK, from these responses I'm thinking that this isn't gonna work. If the diamagnets aren't going to be strong, and alot of energy will be lost through the rolling of the spheres, then I might as well scrap the concept.


    Here is the original concept.
    Are there any ways (at all) to make this function "forever"? (and by forever I mean for a long time, similar to a Newton's Cradle.) I don't care about the power source, whether it be magnets, physics, or whatever. I am open to any and all solutions.

    Thanks for any help.
  6. Jul 15, 2010 #5
    You could make something similar to Newton's cradle and use ordinary magnets.

    If you suspend each magnet by 4 cords so that it can't twist round, and set them with like poles facing, it should work exactly the same.

    (swing boats principle)
  7. Jul 15, 2010 #6

    I like the concept, although I'm not sure of whether or not the neodynium would be strong enough to break the string and spin and attach itself to the magnet. That stuff is strong.
  8. Jul 15, 2010 #7
    Then use a rigid coupling and good quality bearings. The initial twisting moment will be small.
  9. Jul 15, 2010 #8
    Interesting thought. I might have to roll with that.

    Any other ideas?
  10. Jul 15, 2010 #9
    Last edited by a moderator: Apr 25, 2017
  11. Jul 15, 2010 #10
    Very nice. I'm just looking for some cool simple homemade executive toy to put on my desk (It was going to be a Swinging Sticks Kinetic Sculpture like Pepper Potts' but they cost too much and I want it to be homemade.)

    I think I might be able to try your design (but I gotta gather the materials first.) I'm still open to other cool executive toy ideas.

    OK here is another epic idea:

    Have you heard of gauss magnet cannons?


    Basically, if I fix a neodymium magnet in the middle of a ramp, have a ball attached on one side, then drop a sphere from the other side, can I not create an effect in which the second sphere is fired, stops because of the slope, and make it come back and create an equal effect back in the other direction? Thus creating "perpetual motion?"

    Pictures to follow. Share your thoughts.
    Last edited by a moderator: Apr 25, 2017
  12. Jul 16, 2010 #11


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    Neodymium magnets are too strong for this as when they hit each other the force is so great that small deformation will occur at the contact piont. That is another loss to ad. Plus that magnets are slowed down by any metal in close proximity, so tricky usable materials (Plastic is a sad material for a desk toy).
  13. Jul 16, 2010 #12
    Well so the magnet deteriorates. It will still last a long time, and its more just a cool thing to put in motion when I feel the desire to.

    Also the base will be designed out of wood, not plastic, so...

    Pics to come soon

    EDIT: And here it is.


    Furthest ball dropped, 'Gauss' occurs, closest ball goes up ramp, then comes back down, more 'Gauss' occurs, and furthest ball is flung back up again. And that's all with only gravity and magnets.
    Last edited: Jul 16, 2010
  14. Jul 17, 2010 #13


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    I'm not talking about long lasting magnets, i wanna tell you that by using magnets you add more loss to the system as they deform so the long-lasting motion in newtons cradle won't be that long in your case.

    The last CAD (is it SolidW?)pic has a nice ideea but inevitably there will be some friction between balls and wood =)). Again the motion won't last that long.
  15. Jul 17, 2010 #14
    My thought is that if the Gauss effect happens once, then speed will instantly be gained. Then the sphere will reach the top of the arch, and get renewed with the same amount of energy as it originally had on the other side. This renewal of energy should be permanent.

    And if any deterioration occurs, it would happen between the two outer ball bearings and the ball bearings they touch. If you have ever seen a Gauss Cannon function, you would know what I mean.

    P.S. No I designed it in AutoCAD Inventor
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