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Is there any way to find an angle so that polygons' vertexes perfectly intersect?

m_p381m_p381 Member Posts: 3 ✭
in Community Support
I have been trying to find a model of this shape for a while now. Since I wasn't able to I got an Onshape account and attempted to create it. I wasn't able to get the exact angle between the pentagon and the hexagon from Wikipedia but was able to get it to a point where it looked the same when zoomed out through brute force. However, now I am unable to enclose the shape. How do I find the right angle?

Answers

  • NeilCookeNeilCooke Moderator, Onshape Employees Posts: 5,714
    I think your best bet would be to assemble the sketches (in an assembly) then once complete, use in-context editing to copy the sketches into a part studio (using offset surface) - then enclose.
    Senior Director, Technical Services, EMEAI
  • S1monS1mon Member Posts: 3,043 PRO
    This site doesn't seem to have the shape that you want, but there may be some useful info here, if you haven't already seen it: https://polyhedra.tessera.li/
  • Marc_MillerMarc_Miller Member Posts: 110 ✭✭✭
    edited August 2020
    Your post inspired me to check this form out and explore how to construct it.  I saw the angles on the wiki listed as 142.62 and 148.28, but also saw somewhere those calculated as 142.6166666... and 148.2833333... (repeating).  I don't know what level of precision is required to make things properly work out in Onshape, but I entered a few more decimal places for my angles.

    Edit:  Trying enclose at the end fails for me too, but I can select all my geometry and boolean it together into a single part so it feel like this somewhat worked correctly.  (If there were duplicate parts overlapping made from the circular patterns then sometimes the boolean would fail.)  I didn't try your specific excavated version either.

    Here's my file.
    https://cad.onshape.com/documents/7d72a1c9f69ef744e48d88e3/w/07e68f5c387e1d44bc15f3ef/e/873d224f38e4b03883e608b4



    And me just making up something fun.

  • steve_shubinsteve_shubin Member Posts: 1,096 ✭✭✭✭
    edited August 2020

    @m_p381

    There was a link to a document here

    It has been trashed

    The post below has the updated document


    YOU ASKED —

    Is there any way to find an angle so that polygons' vertexes perfectly intersect?


    2nd Paragraph below has been edited to add PATTERN

    THE ANSWER IS —

    there is a way to get all of the vertexes to be coincident. You do not have to bother with calculating the NUMERIC VALUE of any angle. And yet you can still find the correct angle needed.

    If you step through the first five sketches, you will see how to find the proper angle. Once you get that, all you have to do is pattern, mirror, and rotate

    Being as every line segment on this part is the same length, there was only one dimension entered for the entire part. And that was done in the very first sketch.

    Now being as you were wanting to do this using sketches only, well I did it with surfaces — which have no thickness

    Because all the surfaces fit perfectly, I did not have to use ENCLOSE. I just used BOOLEAN to union the surfaces together to make a single solid part

    If I spent more time, I probably could’ve eliminated some steps by not doing as many copy/rotates. But that was not a big concern for me. The main thing was showing how to get that angle and also how you’re gonna do a mirror here or there and some rotates to finish it off

    I followed the example that @Marc_Miller gave in showing the basic shape only, and not showing any concave portions. Because frankly, it was too hard for me to look at all those translucent sketches and figure out exactly what was going on

    you’ve got the basic shape in this document. You could take it the rest of the way by just following the examples given herein


  • steve_shubinsteve_shubin Member Posts: 1,096 ✭✭✭✭
    edited August 2020
    @m_p381

    https://cad.onshape.com/documents/df94b099b76450bd6b3ac02b/w/7b8476ad5003f5d9c29c308a/e/c880e583c66cfc5a23f64d8f

    One of the features was not fully constrained. I fixed that

    Then I added a variable at the very start of all the features in the features list. That variable being #L

    So now, if you change the VALUE for that variable, everything else will change accordingly



  • steve_shubinsteve_shubin Member Posts: 1,096 ✭✭✭✭
    edited August 2020
    @m_p381

    https://cad.onshape.com/documents/df94b099b76450bd6b3ac02b/w/7b8476ad5003f5d9c29c308a/e/c880e583c66cfc5a23f64d8f

    I cleaned up the way all the patterns, rotates, and mirrors were done on this 62 sided polyhedron

    This eliminated 13 steps compared to my ORIGINAL document





  • Marc_MillerMarc_Miller Member Posts: 110 ✭✭✭
    My friend wanted one.  And printed with glow in the dark filament.

    It's about 3.25" in diameter.




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