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Rhombic Triacontahedron (Internally supported)

PostPosted: Tue Nov 24, 2009 5:34 pm
by Wim
I really like the looks of the internally supported Rhombic Triacontahedron, and have been trying to build one. First I tried using the pictures Karl put on Flickr, and then I discovered that it was on the Wiki with build instructions (

However, even with the current build instructions on the Wiki I fail at building it, invariably ending with a heap of magnets and support struts that don't fit.

Can anyone post some pictures of the beginning and intermediate stages of construction?

Re: Rhombic Triacontahedron (Internally supported)

PostPosted: Tue Nov 24, 2009 6:33 pm
by Peter Jepsen
Oh, that one!
You just need some of those Golden Rhombus panels and it's easy peasy.

I managed to do it by first carefully trying to build the outside part (yellow bars) as a shell without any supports. Yes, it will be flimsy but shouldn't collapse. Next, with that 'shell' in place, it helps me find out where the 3-long bars have to start and end. Meaning that starting from a particular sphere, there are only three other spheres at a 3-bars distance away from that one.
The nicest part in my opinion is that when it's all finished and nice, then you remove all the 'outer shell' bars and the 5 entangled tetrahedra (triangular pyramids) are all that reamins.
[ ... Tetrahedra ]
Bravo Amafirlian for discovering that one!

Re: Rhombic Triacontahedron (Internally supported)

PostPosted: Tue Nov 24, 2009 8:56 pm
by Wim
Ah, so basically this is the 90 bar sphere (not sure what its official name is, but it consists of 12 pentagons basically). That makes sense.

Although once I built it with ALL diagonals in place, I could only add two of the tetras since they unhinge the structure a little. Building the third proved impossible to complete using Supermag (which is a pain to use for multi-bar rods anyway, and the near-miss may be worse since the bar length is slightly different too). Guess I'll have to wait until I'm home to try it. I'm just impatient.

Thanks for the info Peter. At least I know what basic structure to build now (I'll probably build it with the rhombi, since I normally hardly ever get to use them).

Re: Rhombic Triacontahedron (Internally supported)

PostPosted: Wed Nov 25, 2009 5:44 am
by Wim
With Geomag it's a lot easier, although I'm pretty sure that this afternoon I made some mistakes while attempting to build it with Supermag.

1. I simply built a dodecahedron out of white, but instead of 5-sided panels I used 5 bars in a star pattern in an alternate color (green in this case). The result is the outside of the Rhombic Triacontahedron.
2. Looking purely at the green bars, find a ball with 3 green bars and remove one of the white bars.
3. Insert a bar made of 3 rods in a different color into the structure where the removed white bar was. On the opposite end (4 green bars away or wherever it fits best basically) remove the white rod that's in the way.
4. Repeat steps 2 and 3 until you have a triangle, then a tetra inside the dodecahedron.
5. Repeat steps 2, 3 and 4 until there are no more white bars and every ball with 3 green bars on it is now also a point of a tetra.

It's a bit of a tight fit, and a little tricky to get all those bars inside the structure, but I really like the result and I'm glad I built it.
Completed structure in green.

All green bars removed.

White instead of green at my wife's request.

Many thanks to Amafirlian for discovering it, Karl for the inspiration (since it was his photo I saw first and wanted to reproduce), and Peter for the build tip.

Re: Rhombic Triacontahedron (Internally supported)

PostPosted: Sat Oct 23, 2010 5:26 pm
by geomagmasters
I realize this post is a year old but since I'm new I wanted to share my Rhombic Triacontahedron. I have building instructions on my web site: the instructions are on the page.