Making 3V 5/9 Icosahedron Dome by using Geodome

Geodome is open source Geodesic Dome design software. I installed it from the source tarball.

To make a 3V 5/9 Icosahedron dome explained on SimplyDifferently.org page, you need to remove the bottom row.

Main dome design program’s name is dome. I changed its name to geodome.

Starting Geodome by radius 1 foot.
$ geodome -radius 1

To generate frequency, press desired number i.e. number key 3 would create a frequency three dome. Right mouse button shows popup menu that has main features. Normalize will transform the icosahedron into a dome. To save the dome data, press right mouse button and select save. Pressing Escape key exits the program.


$ more r12v3.data
radius: 12
76 vertices:
0: 0,0,12
1: 1.27127,-3.91258,11.256
2: 4.11393,0,11.256
3: 2.54254,-7.82515,8.71344
4: 5.88138,-4.27307,9.51627
5: 8.22785,0,8.71344
6: 3.31672,-10.2078,5.36657
[snip]

The following images show how I removed the bottom row. The easiest way to remove the bottom row is turning off face on the menu, then use Rotate and Delete Elements menu accordingly. When Delete Elements is selected, use left mouse button to delete the selected object: edge, vertex. Clicking a vertex erases the adjacent edges.

v3dome_1row_less

v3dome_1row_less2

v3dome_1row_less3

Default 3V 5/9 dome has 210 struts. Removing the bottom row from 3V 5/9 dome reduces it to 165 struts, which matches the specs on SimplyDifferently.org. To calculate total number of struts and bending angles, uses dome_struts program like below. The unit of length Geodome uses is foot. So anyone who uses metric system must convert final data to desired metric unit: meter, centimeter, or millimeter.


$ dome_struts v3dome_1row_less.data > v3dome_1row_less_struts.data


165 struts total, 3 different lengths

strut count length a0 a1 length2 cut length
A 80 0.412 12 12 0.414 0.539
B 55 0.403 12 12 0.406 0.531
C 30 0.348 10 10 0.350 0.475

Notes:

length: distance from vertex to vertex
a0, a1: bend angles at the two ends
length2: distance between bolt holes (accounts for bends)
cut length: total strut length, including margins

Don't forget to make a few extras

Default 3V 5/9 dome’s strut data Geodome generates by flattening the bottom.

210 struts total, 5 different lengths

strut count length a0 a1 length2 cut length
A 90 4.941 12 12 4.943 5.068
B 70 4.836 12 12 4.839 4.964
C 30 4.181 10 10 4.183 4.308
D 10 4.842 7 16 4.845 4.970
E 10 4.103 15 4 4.105 4.230

Notes:

length: distance from vertex to vertex
a0, a1: bend angles at the two ends
length2: distance between bolt holes (accounts for bends)
cut length: total strut length, including margins

Don't forget to make a few extras

About janpenguin

Email: janpenguin [at] riseup [dot] net Every content on the blog is made by Free and Open Source Software in GNU/Linux.
This entry was posted in Permaculture, Science and technologies and tagged , , , . Bookmark the permalink.

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