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  • making polyhedrons

    I have been given a large stack of 3 inch angle iron scraps. I have the idea to make polyhedron out of it using the corner as the line that forms the edge of each face. I am having trouble figuring out the angle to cut each leg so that the pieces fit together. Can anyone give me some ideas on how to determine the angles?

  • #2
    pretty crude, but I often use posterboard for figuring out odd angles and such.

    Dave
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    • #3
      There are a lot of different polyhedrons.
      --- RJL ----------------------------------------------

      Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
      -------------------------

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      • #4
        Originally posted by usmcpop View Post
        There are a lot of different polyhedrons.
        ...and no agreed-upon definition, it seems!
        "Good Enough Never Is"

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        • #5
          In a polygon (flat thing with N sides) the total included angle at each corner is 180 - 360/N. The cut angle is 1/2 that.
          Regular polyhedrons have all faces made from the same polygon. In that adjoining face, the cut angles will be the same BUT in the other face of the angle iron.
          There is a 'gotcha' ! Standard angle iron will work great for a hexahedron (AKA a cube) since the angle is 90 degrees. For all others, the angle between the faces of the angle iron also needs to have this same angle for it to really fit right.
          The poster board (I prefer 1/4" foam-core board) and hot melt glue are a great way to experiment. With either of these you can easily make 'angle iron' with non-standard angles.

          Bob

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          • #6
            . o O (Boy's making some gaming dice out of metal scraps ... ) A big Dungeons and Dragons fan, are you?

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            • #7
              I was in dungeons and dragons as a kid but I am thinking of something much bigger than game dice. Bob nailed my problem. In order to get the legs of the angle iron the same distance from the plane of each face the angle that would be cut should be different than the angle of the vertices. Right now I am only thinking of tackling the regular polygons. Al the angles of the faces are the same. I will wait to try one of the 92 Johnson solids for later. I have also thought that I could just cut the angle iron length wise at the corner and make a frame then weld the frames together at the proper angle but what is the challenge in that.

              How ever I end up making them I want to mount the shapes on posts in my yard. I live near a high school so it could be interesting to see if they get noticed

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              • #8
                Ted71,

                When you master the regulars you might want to look at the Fullerenes. Most famous, of course, is the Bucky Ball (AKA socker ball and carbon60). There are a whole bunch of variations of polyhedra using only pentagons and hexagons.

                Here is a starting link.
                http://www.chemistry.wustl.edu/~edud...ene.html#index There are sites to download 3D cordinates for them.
                Enjoy.

                Bob

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