## Wall Thickness

### Wall Thickness

I am making plutonic objects out of wood. I have had resonalble success. I want to take the objects I make, put them in a wood lathe and turn them into spheres. Does anyone know how to calculate the thickness of the wood before it is turned to achieve a final wall thickness of 1/2"

Hamp

Hamp

Well, the wood will be thinnest in the corners and thickest at the centre of each piece. Assuming you want at least 1/2" everywhere, you need to:

Take the difference between the inradius (radius of the sphere tangent to the faces at their centres) and the out- or exradius (of the sphere tanget to the vertices). That tells you how much fatter each piece is in the middle.

As a rough approximation, add 1/2" to get the starting thickness. You could calculate more accurately but it would depend on some complicated angles of each Platonic, so personally I'd just round the number off to a handy thickness - if it's a tetrahedron I'd round down.

HTH

Take the difference between the inradius (radius of the sphere tangent to the faces at their centres) and the out- or exradius (of the sphere tanget to the vertices). That tells you how much fatter each piece is in the middle.

As a rough approximation, add 1/2" to get the starting thickness. You could calculate more accurately but it would depend on some complicated angles of each Platonic, so personally I'd just round the number off to a handy thickness - if it's a tetrahedron I'd round down.

HTH

Cheers,

Guy. Guy's polyhedra pages

Guy. Guy's polyhedra pages

This week end I was able to build a "Rhombicosidodecahedron". I had good success for a first shot. I made it out of MDF plywood since it was prototype. It is about 13" in dia. I'll post a picture as soon as I can get my hands on a digital camera.

thanks for your help.

- robertw
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**Posts:**532**Joined:**Thu Jan 10, 2008 6:47 am**Location:**Melbourne, Australia-
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See this thread, about posting images: http://software3d.com/Forums/viewtopic.php?t=23

No, I don't post images of real models (except the odd icosahedron in a museum that I think may have been made by H.T. Flather of Coxeter, Du Val, Flather and Petrie fame).robertw wrote:I presume that question's for Guy? I only make models from paper. Just wanted to answer the part of the question I could

And yes, circumradius is the usual term. I knew that.

Cheers,

Guy. Guy's polyhedra pages

Guy. Guy's polyhedra pages

### archimedan rhombicosidodecahedron

If am building a "archimedan rhombicosidodecahedron" how do I calculate the # of vertices?

Thanks,

Hamp

Thanks,

Hamp