How it Works

The dome you are looking at is based on a classical construction by Plato, a Greek mathematician. He inscribed twenty triangles of equal size inside of a sphere and it was named an icosahedron (greek for 20 sided.) Later, another mathematician by the name of Archimedes divided each of the sides of Plato’s triangles into three equal segments. This was called “truncating“. The assembly became known as a “Truncated Icosahedron” and is probably most familiar as a multi-faceted soccer ball.

The advantage of this design is that the connectors (joints) are identical and can be used at any intersection of the straight segments. The straight segments determine the size of the dome or sphere. All of the straight segments (2” ABS pipe) must be the same length for any given diameter. The size limit is when the straight segments begin to bend (deflect.) An average person (200lbs.) who stood on a straight segment (as in a jungle gym) that was thirty two inches long, will bend it. That means you should not build a jungle gym larger than a 13 foot diameter. If you have plants in pots with soil you should limit the load on any one segment to about 50lbs. They’ll get heavier when you water them.

All loads transfer through the joints and straight sections to the ground. The structure does not have to be level but all of the feet must contact the ground for maximum strength.  A tennis ball inserted in open connection makes a great foot and you can shim any feet that don’t touch the ground with anything handy, like stones or pieces of plywood. The strongest assembly is with all joints glued. You cannot take it apart if you do that. I recommend gluing the sub-assemblies, the pentagons and half hexagons, and leaving the straight connection links to be fastened with screws. Use one to test the assembly for size and use and increase that to three when using the dome to support loads. If you are building a teaching aid or just having fun with the kids, building a puzzle, than you can use just one screw in the hole provided and it makes disassembly easy and the whole assembly very compact to travel or store. Have fun.