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Armature: Magnetic Joints

January 13, 2018

Click on photo below or HERE for my commentary and bigger photo ….

Armature – Magnetic Joints

Revisiting OSSA (2016) … I posted in past here….

Posted by Stop Motion Works on Saturday, December 30, 2017

Topics: Behind the Scenes, Stop Motion, Stop Motion Armatures | 1 Comment »

One Response to “Armature: Magnetic Joints”

  1. Ron Cole says:

    Beware magnetic joints! Don’t avoid them, just beware of their behavior… I’ve used magnets for joints and in the right circumstances they can be a great solution. But you need to be aware that the magnetic field around a magnet can be complex and not ‘like’ to stay connected in some ways.

    Everyone knows that magnets have poles, as in positive and negative but did you know that the magnetic lines that travel around magnets can have angles ‘they prefers’ and others it does not when you line them up with each other? If you’re like me, you probably didn’t know that. Let me explain…

    I used four magnets to act as the hinge for a skeleton puppet, the jawbone had two magnets and there were two magnets in the skull they lined up with. When I brought the jaw near the skull, it just snapped itself on in the perfect position. Marvelous! right? Well then it got a little complicated when I realized that the jaw had certain angles of openness that it didn’t ‘like’ to be in as the magnets rotated against one another.

    After playing with the problem for a while, I found that I needed to remove the magnets and glue them back in again after testing and properly aligning them. It seems that those pesky magnetic field lines are stronger in some areas of rotation than in other they conflict. The magnets always stuck to each other as you would expect, but in some positions of rotation that bond was stronger than in other positioins.

    The skull I was making was of a deer and so the jaw was long and so leverage was an issue… the magnets needed to be able to support weight. So the bond between the magnets might feel strong where the jaw was closed and where it was fully open but weak in the middle (or vise/versa) and so the jaw might not be able to hold it’s position so well in some spots.

    All I needed to do to solve the problem was glue the magnets into the jaw and attach the other two and while holding them, move the jaw to find where the weak and strong spots were – draw a line on the magnet to remind me of the best position when I take those other magnets and glue them into the skull… problem solved.

    Now you might think that using a magnet against at steel ball might not present the same problem but I’ll remind you that magnets turn steel into other magnets when pressed against it over a period of time. Let that magnet stay on that ball long enough and you will have a magnetic ball. I have no idea if this will be a problem of any kind but after my experience with the magnetic jaw, it’s just something to bear in mind if you run into unexpected weak spots.

    That’s my 2¢ worth. :)


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