Doubt about a dome in Teufelsberg

[Gaizka Altuna Charterina]

Dear all, 

I’d love your insight on a question about a geodesic dome. A few days ago, I visited Teufelsberg in Berlin, the former Cold War listening station. One of its domes caught my attention: it seems that its design starting point is not on an icosahedron, but a dodecahedron. From what I observed, a pentagon appears at each vertex of the main dodecahedron pentagons, plus one in the center, all connected with triangles—creating nodes where seven struts meet.

Given the site’s technical origins, there may be specific reasons for this choice, but I wonder if anyone can offer a geometric, fabrication, or structural explanation for why this subdivision was used instead of a typical Class I or II icosahedral one.

I’m attaching photos of the dome.
Many thanks in advance!

  

[Paul Kranz]

Gaizka: I added the dome to Domes of the World Map. Paul sends...

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Very high regards,

 

Paul C. Kranz, LMFT

Kranz & Associates, LLC

ReviveTheFlame.com

[TaffGoch]

Gaizka,

An apparent random pattern is not uncommon for radomes. 

A regular icosa or dodeca pattern produces interference in the radar image. 

Here is an example of the pseudo-random pattern of a radome, showing how it deviates from an icosa subdivision:

https://www.deviantart.com/taffgoch/art/FL-Radome-510107677

Not TOTALLY random, after all.

~Taff

(aka; TaffGoch, David Price)

[TaffGoch]

Gaizka,

Here is the pseudo-random subdivision of the Teufelsberg radome:

The whole geometry of the icosa is "tilted," which improves the non-interference of radar imagery

 (since the rib pattern is not repeated during 360-degree rotation of the radar dish.)

[Dick Fischbeck]

How many pentagons, hexagons and heptagons if it were a complete sphere? 

Is there one heptagon for each pentagon in excess of 12?

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[Dick Fischbeck]

AI said this which is wrong: "Heptagons induce negative curvature, which creates weak points and complex stress distributions that can lead to structural failure or the need for excessive additional support."

I can't find a source for it. I hear AI makes stuff up sometimes.

[Gaizka Altuna Charterina]

Dear all,

Thank you very much for all the insight you’ve shared.

@TaffGoch, thank you for the explanation. I had no idea that regular patterns could affect antenna signals. And thank you as well for taking the time to draw the pattern diagram — I really appreciate it. It clarifies the dome pattern really well.

@Paul, thanks for adding the case to the map. I’ll share more radomes in Germany in the Map thread.

@Dick, perhaps I didn’t explain the issue with the pentagons very well. I’m attaching a drawing to show what I meant, although I think TaffGoch’s diagram already clarifies everything much better.

[Chris Kitrick]

I have corrected Taff's diagram with the correct locations of the icosahedron's vertices (red) and the icosa face centers (blue). The icosa triangles are in green.

Cheers,

Chris