Robert Marshall
12-15-2019, 11:00 AM
I am considering assembling a plywood pentakis dodecahedron (12 pentagonal pyramids making up a 3-D geometric shape), and then turning it to a sphere. I would like to be able to do that with a temporary joint along the middle of it, so that after turning, it can be taken apart into two pieces. Here is a wire-frame diagram of the geometric shape.
421554
My plan is to assemble the pentagonal pyramids first, making sure they are identical to each other. Then, glue together 6 pyramids into half of the final shape, and glue together the other six pyramids into the other half. Then, temporarily join the two halves, to be put on the lathe and turned into a sphere. So my question concerns how to accomplish this temporary joinder between the two halves, for turning, so that after turning, I can take the two halves apart.
Here is a screen-shot from a YouTube video about building a plywood dodecahedron. That shape differs from the one I intend to build, in that each of the 12 pentagons is a single flat piece of plywood, whereas my project would be using pentagonal pyramids instead of flat pentagons. I don't think that difference matters, however, with respect to my purpose. As you can see from this photo, the half-assembled dodecahedron consists of one pentagon at the bottom, and five pentagons joined to it (and to each other). It gives you a five-pointed zig-zag "equator", to which the other assembled half should match up to form the full dodecahedron. It seems to me that the zig-zag shape of the joint will itself impart some strength (rotational resistance) to the temporary joint, as compared to something with a straight "equator."
421553
So, how would you suggest I temporarily join the two halves of the dodecahedron to each other, in order to place it on the lathe between centers for turning to a sphere, and allowing it to be disassembled into the two halves, after turning? I've thought about double-sided tape, or hot glue; looking for suggestions on these or any other temporary joint ideas you might have.
Thanks.
Robert
421554
My plan is to assemble the pentagonal pyramids first, making sure they are identical to each other. Then, glue together 6 pyramids into half of the final shape, and glue together the other six pyramids into the other half. Then, temporarily join the two halves, to be put on the lathe and turned into a sphere. So my question concerns how to accomplish this temporary joinder between the two halves, for turning, so that after turning, I can take the two halves apart.
Here is a screen-shot from a YouTube video about building a plywood dodecahedron. That shape differs from the one I intend to build, in that each of the 12 pentagons is a single flat piece of plywood, whereas my project would be using pentagonal pyramids instead of flat pentagons. I don't think that difference matters, however, with respect to my purpose. As you can see from this photo, the half-assembled dodecahedron consists of one pentagon at the bottom, and five pentagons joined to it (and to each other). It gives you a five-pointed zig-zag "equator", to which the other assembled half should match up to form the full dodecahedron. It seems to me that the zig-zag shape of the joint will itself impart some strength (rotational resistance) to the temporary joint, as compared to something with a straight "equator."
421553
So, how would you suggest I temporarily join the two halves of the dodecahedron to each other, in order to place it on the lathe between centers for turning to a sphere, and allowing it to be disassembled into the two halves, after turning? I've thought about double-sided tape, or hot glue; looking for suggestions on these or any other temporary joint ideas you might have.
Thanks.
Robert