Introduction: 8ft Icosahedron

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About: My name is Jack Defay and I am a student and a maker! Check out my work on Youtube @jackandbendefayrobotics | Thingiverse @jackdefay | Github @jackdefay

You might be thinking, why build an 8 foot tall Icosahedron? For only $20 and a weekend, why not?

For this project all you will need is

- 150 ft of 1/2 in inner diameter PVC pipe

- access to a 3D printer

Step 1: What Is an Icosahedron?

The Icosahedron is a platonic solid like a cube or a tetrahedron. An Icosahedron is the largest of the platonic solids, made up entirely of equilateral triangle faces. This gives it strength and volume, which is why this shape is repeated so often throughout nature.

Platonic solids are just polyhedra with regular congruent polygon faces. Any connector piece will be symmetric and all of the connectors will be identical. This also means that all of the side lengths are equal. The symmetry makes them way easier to make!

Step 2: Connectors

This step might take a while because you have to wait for it to print. Check out my connector model on thingiverse:

https://www.thingiverse.com/thing:3403966

and print out 12 copies.

At first I printed these with 3 walls and 20% infill, which worked great for the 3ft icosahedron. The 3 wall connectors were a bit fragile for the longer pipes so I beefed them up to 5 walls. I've had trouble with 3D printed cylinders like this used to connect things, but the way it layers along the diagonal of the cylinders greatly improves the strength of the part.

I designed these in Solidworks to fit snugly in this size pipe. If you want to use a larger diameter pipe it should be straight forwards to scale it up to match. I've also included my earlier models for the tetrahedron and cube if you feel like making different gigantic shapes!

Step 3: PVC Pipes

I chose PVC pipe to form the edges of the shape because I needed a material that is cheap, strong, and comes in reasonably small tube shapes. I picked up 100ft of half inch internal diameter pipe at home depot for just over $10, this means with side length of 5ft, the 8ft Icosahedron costs only $15 in pipe.

To cut the pipe, I would definitely suggest investing in a ratchet. This is a simple tool that makes cutting the pipe a breeze. To cut the pipe, take a tape measure and a sharpie, mark the length and cut it with the ratchet. This could also be done with a hacksaw but seriously the ratchet was so much better.

These pipes come in 10ft lengths, which made 2ft and 5ft sides the natural choices. I first tried a 2ft length Icosahedron, which had a height of only about 3ft. This was cool, but I honestly thought it would be a little...bigger. So I bought some more pipe and cut 5ft lengths. Within the hour I had constructed an Icosahedron as big as my deck!

Step 4: Construction

Construction is super simple. For smaller sizes it's easy enough to do alone, but I found for the really big one a helping hand or two goes a long way. These connectors are friction fit, so all you have to do is cut the pipes to length and jam them in.

Each pipe fit a little differently. Some of them were perfect, some a little loose, and some nearly impossible to fit together. I found that they were hardly ever so loose that they fell out, but there were several pipes that I couldn't get all the way in. For the ones that were really stuck, I found twisting to work the best. Just make sure you're careful not to bend the connector as it can snap.

When assembling the big Icosahedron, one of the connectors broke and I repaired it with some duct tape. It's been outside for two weeks now and still holding great so I guess duct tape works well for this sort of thing! Also, I would advise printing backup connectors...

Step 5: Painting!

Painting the icosahedron takes it from cool to awesome.To paint the pipes properly you should clean them with a wet paper towel, sand with a fine grit sandpaper, wipe with acetone, prime and then paint. Honestly that's a lot of work so I just used an all purpose plastic primer and them painted. It worked great!

At first I tried spray painting it standing up but wasted a ton of paint to the wind. The next time I took it apart and laid the pipes next to each other to get better coverage. Gold looked great on the tetrahedron and I'll paint the big icosahedron when it warms up!

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