• MaxwellMaxwell November 2016
    Hey, so I've been wondering about magnets with more complex shapes than the standard cylinder. It seems to me that something like a torus would provide a significantly higher ratio of surface area to volume while also increasing the ability of the body to anchor the magnet. Barring the additional cost of manufacture, what are the specific drawbacks of something like this?
  • CassoxCassox November 2016
    A torus produces a non optimal field shape but I totally understand what you're getting at. A concave disc would be pretty optimal. It focuses the field like a satellite dish towards a center point. I could find no one willing to manufacture this shape. However...

    Its be pretty easy to do with a drummel. You'd need the ability to coat it immediately though as the shot degrades from the moisture in air in no time. You could probably electroplate something on.
  • CassoxCassox November 2016
    I could never master the formulas to predict fields but it can be done even for complex shapes. I found some software once that does it for you but couldn't find a ver. I could get my hands on. I'll try to find it and maybe someone will have better luck. Perhaps access through a uni. I was also looking into making a tiny halbach array but the parts would just need to be to damn small.
  • CassoxCassox November 2016
    Of course I was only interested in finger mags at the time. You could probably make a halbach for the outer hand. Also you could look into shielding. Certain metals can basically reflect (not exactly but close enough) fields or shape them. I never figured out a way to make this more effective then simply having it be all magnet.. But once again maybe someone with new eyes could figure it out.
  • JupiterJupiter November 2016
    @Cassox You've peaked my interest. What use for an implantable Halbach Array have you got?
  • MaxwellMaxwell November 2016
    @Cassox What would you define as an optimal field shape and how does it affect the sensations in the body?
  • CassoxCassox November 2016
    @Jupiter.. I have no particular use but it would be pretty cool in that a Halbach array focuses nearly all of the magnetic field on one side of a magnet. A lot of field is wasted on the side of the magnet deep to the body. The point would be doubling the effective strength of a magnet without increasing size.

    @Maxwell.. Gee, with a moniker of Maxwell I'm not sure I should get into a physics discussion. Take a look at this:

    https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US5929732.pdf

    Badass eh? Point is to focus the field along a single axis as much as possible.
    I think I get where you're going with the torus shape but I'm interpreting it as being the equivalent of a ring shaped magnet unless you're getting at an electromagnet. I mean all the cool toroidal field stuff is related to loops of wire carrying current no?
    I'm not sure how to answer that question.. I guess whatever field shape that is able to produce sensation from the farthest distance with the minimal size of magnet? Perhaps a few different shapes would be best.. something giving a very broad field.. another giving a very small but intense field. I'm not sure.
  • CassoxCassox November 2016
    Oh shit! This looks promising: 

     https://sourceforge.net/projects/maxfem/

    https://sourceforge.net/projects/elmerfem/
  • BenbeezyBenbeezy November 2016
    I have had a lot of shapes of magnets and the torus shape was cool because it for sure didnt move or flip because I did heal threw the hole in the middle (cas took one out of me and it was kinda crazy) but the field from it was very short range, I could pick up metal things better since the field is much better then very close but bad at a distance. So fine for picking things up but bad for feeling anything. Ball shapes are weird and I don't like, disks are the go to for a reason. I do think a hallback array would be kick ass but it's hard to make one that is small enough to implant. not saying it's impossible but it's harder.

    @Cassox those programs look awesome 
  • JoshJosh November 2016
    What's weird about the sphere shaped ones? Does it work just as well as a disk shaped magnets? I would guess the ball turning might feel weird, but is that the only downside?
  • BenbeezyBenbeezy November 2016
    What I notice I feel with the disk is that it has a push and a pull. Where a ball has just pull (since it will just role over) and with no edge so it's averaged and kinda dull of a feeling. 
  • JupiterJupiter November 2016
    I've had a thought, keeping in mind I didn't read any large bits of information regarding halbach designs, but...
    If a Halbach Array is constructed by alternating magnet layout patterns, and only half of said magnets are physically pointing in a direction, we'll say "out". And the resulting design focuses all the magnetic fields from the magnets in one direction, "out". Then you have say 100 physical magnets, 50 of which point "out", 100 of which have fields focused "outward", 0 of which have reverse fields focused the other way.

    This just started to make a little sense, if the magenta don't have a reversed field on the opposite side then this idea makes sense. Talking through things out loud (or while typing them) sometimes helps me realize things as I slow down and picture the scenario in my head.

    Wouldn't the same affect be achieved by having 100 magnets all facing "out"? That is, isn't the benefit to a Halbach Array that there's no field on the "inside", rather than the "outside" field being stronger? I would think for the purposes of implanting it wouldn't be particularly beneficial to lack a reverse sided field on the back side of a magnet. I'm thinking specifically about sensing magnets in this case.
  • CassoxCassox November 2016
    Nah. A halbach focuses the field on one side resulting in a more powerful field. That's the real advantage.
  • MaxwellMaxwell November 2016
    @Benbeezy I would still be interested in working with some toroidal magnets, maybe see if I can compensate for the disadvantages. What can you tell me about the one that you had implanted? Dimensions, coating, etc.

    As for the Halbach, I had a thought. Not totally sure this would work, but what if we had a series of five cylindrical magnets of m31 dimensions, two of which had axes of magnetization at ninety degrees to the standard configuration, and laid them base to base in the correct order to form a Halbach array? The final product would be slightly smaller than the m63.
  • BirdhandzBirdhandz November 2016
    There's some good information in this thread that might be nice if it made its way to the Wiki page.

    I'm specifically talking about @Benbeezy's comments about the feeling for different shapes of magnets but I have seen some other posts with little tidbits of knowledge sometimes hidden in unrelated threads making them hard to find.

    If somebody wanted to take the time to edit the Wiki site and wanted to copy/paste from a comment, should you try to credit the one who made the original comment or is it best to keep the "HE said, She said" to a minimum.  In this particular case, the one making the comment should have a lot of credibility considering the number of implants he has personally had but many times it is someone just repeating stuff they heard somewhere else.  I'm going to assume you should just use your own judgement when messing around with the Wiki and maybe someone else will fix it if that judgement wasn't good enough.