Reuleaux Triangle Spheroforms

Discussion in 'My Shapeways Order Arrived' started by ualrkids, Mar 31, 2010.

  1. ualrkids
    ualrkids New Member
    This is my first order from shapeways. These are reuleaux trianlges(commonly used in rotary engines) rotated about one of its vertices. The interesting property of this shape is its ability to roll just like a sphere, meaning that it has a constant width regardless of orientation. I am very pleased with the results.


    nicks triangles 001.jpg

    nicks triangles 002.jpg

    Sorry for not giving any sense of the scale. They are about the size of a quarter. Here is a link to my shop: http://www.shapeways.com/shops/greatgeometers.
     
    Last edited: Apr 1, 2010
  2. RalphVdB
    RalphVdB Well-Known Member CS Team
    HI ualrkids

    i actuality saw this model, but i was wondering what it was for. Now i know, enjoy your models ;)
     
  3. gibell
    gibell Well-Known Member
    Very cool!! Nice idea!

    How about making them larger, and hollow?
     
  4. rawkstar320
    rawkstar320 New Member
    rotary engine eh?
    You should consider making a replica rotary engine. That would be awesome. I would probably do it...except that I am really super busy haha.
    Check out my shop when you get a chance, I have a model RC Engine and a 3 Speed Transmission. I really want to revisit the transmission project to make it work correctly.....

    Anyways, those are pretty awesome!

    good luck !!
     
  5. ualrkids
    ualrkids New Member
    I am planning on doing that. These were really just a proof of concept. I wanted to make sure they were precise enough to maintain there physical properties (constant width). I created them using Maple 13, and I'm not sure how to make hollow objects with it. I have some idea, but I'm not really familiar with any 3d modelling tools. I actually made others with more sides, and they also have a constant width. Here's a link to a video that illustrates why they are special.

    http://www.youtube.com/watch?v=jYf3nOYM_mQ&feature=relat ed

     
  6. Ushanka
    Ushanka New Member
    It should be pretty straightforward to hollow those out using just Meshlab! I could help out if you want.

    How well do they roll?
     
  7. ualrkids
    ualrkids New Member
    They actually roll very well. I only ordered two so it makes difficult to keep the book level. If I had three it would make the rolling a lot smoother because I wouldn't have to keep the book perfectly level myself.
     
  8. gibell
    gibell Well-Known Member
    That video is really cool! Three of them, LARGE, in stainless steel would make for a really unusual coffee table base.

    I managed to create one that is hollow (see screen shot below). Let me know if you need any help with this.

    Reuleaux1.jpg
     
  9. ualrkids
    ualrkids New Member
    Do they have to have a hole, or is there a way to make it hollow without one?
     
  10. gibell
    gibell Well-Known Member
    Unfortunately, to be hollow it has to have a hole, or the support material can't be removed. I put the hole in the top where the surface is flattest. But it still might affect the rolling ...
     
  11. ualrkids
    ualrkids New Member
    The top and the bottom could be separate pieces, and then they could either thread together or interlock in some way, so the rolling would be unaffected.
     
  12. rawkstar320
    rawkstar320 New Member
    you could alwasy fill in the hole, or have several small holes that you fill.

    Depending on the size (if its stainless) you might be able to fill the holes with solder or something? Sand it smooth, and you should be good to go.

    Of course, i dont know how easy it is to solder the stainless...but it seems like it might work.

    Coffee table idea: Awesome. I would deff like to see that one made a reality.
     
  13. Ushanka
    Ushanka New Member
    If it's made of one of the strong/flexible materials or Sandstone, then yes, there needs to be a hole in the model. But you don't need a hole for the white/black/transparent detail materials or for grey robust! Those can be hollow and have no escape hole.
     
  14. gibell
    gibell Well-Known Member
    I made some of these on my own. Mine are 3cm in diameter, they are hollowed out but I tried to do something clever to avoid a bump or flat spot when they are rolled over the hole.

    IMG_4303_cropped.jpg

    It's interesting to place these between two books or boards and shift or spin the top board. It feels just like there are marbles rolling between them!

    IMG_4301_cropped.jpg

    You can see lines in these in certain directions. This happened because the print orientation was not as I had planned, they got flipped 90 degrees for some reason.

    IMG_4304_cropped.jpg

    Here is a link to this model in my shop.
     
  15. Youknowwho4eva
    Youknowwho4eva Shapeways Employee Community Team
    The green one looks like a pentagon in the picture, but when I think of the shape, I don't see how it would turn into a pentagon. It hurts my head a little :p. Very awesome idea, I'll have to catch up on rotaries, I've only briefly looked it up a while ago.
     
  16. Ushanka
    Ushanka New Member
    That's because it probably is a pentagon :p

    You can make solids of constant width by rotating any Reuleaux polygon: reuleaux triangles, reuleaux pentagons, reuleaux heptagons...
     
  17. gibell
    gibell Well-Known Member
    Yep, all 3 are different. Blue = Reuleaux triangle, orange = rounded Reuleaux triangle, green = Reuleaux pentagon. Each one is just these 2D shapes turned on axis, making a 3D "solid of revolution". The green one looks a lot like a muffin!!

    I want to make a Meissner Tetrahedron, but I can't quite figure out its shape from the descriptions.
     
  18. Youknowwho4eva
    Youknowwho4eva Shapeways Employee Community Team
  19. ualrkids
    ualrkids New Member
    I wrote a paper on the physical properties of these objects. Thought you all might be interested.
     

    Attached Files:

  20. ualrkids
    ualrkids New Member
    This is the best description I could find, and I couldn't think of a way to make it out of functions in Maple. Maybe you will have more luck.
     

    Attached Files:

    Last edited: Jun 14, 2010