Actions

Tetrahedron

From Trammell Hudson's Projects

Knotted Tetrahedra

Knotted tetrahedra
Knotted tetrahedra

I've been experimenting with 3D printing interlocking tetrahedra. In this example there are five units -- each tetrahedron is inter-woven with four others and shares its vertices with a dodecahedron -- and the entire shape has been intersected with a sphere.

Interlocking colored tetrahedrons
Metal tetrahedron

This example more clearly shows the tetrahedra. The printed version is somewhat fragile and has quite a range of motion. Despite the interlocking, it can be printed on a Makerbot or commercial services like Shapeways can print it in a variety of materials. They did a one-off test print in metal, which looks amazing and weighs a few hundred grams. It is quite hefy and feels great to play with as a jangly desk toy.

The OpenSCAD code to generate it is fairly simple (and can be compressed to fit in a single tweet):

$fn=30;
v=[
        [+1,+1,+1],
        [+1,-1,-1],
        [-1,+1,-1],
        [-1,-1,+1],
];

colors=["red","green","blue","yellow","purple"];

module tetrahedron(len,thick)
{
        for(a=[0:2])
                for(b=[a+1:3])
                        hull() {
                                translate(v[a]*len) sphere(r=thick);
                                translate(v[b]*len) sphere(r=thick);
                        }
}

for(i=[0:4])
{
        color(colors[i])
        rotate([0,-atan(sqrt(5)/2-0.5), i*360/5])
        tetrahedron(20,2);
} 

Add a rotate($t*360) and OpenSCAD will generate a nice animation: