L4 Dome Experiment

3V 5/9 Dome (Kruschke Method) spherical diameter: 15.137 ft height: 8.988 ft base area: 168.554 square ft

Repurposed 1st 4 rows of L4

1v and 2v spheres

L4 Dome Overview ●

Dome frequency: 8v L4 Variant

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Spherical diameter: 42 feet (12.8016 m)

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1st 4 rows of L4 dome dimensions:

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Dome diameter: 22.0808 feet (6.73 m)

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Dome height: 3.1363 feet (95.6 cm)

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Dome base area: 308.5195 sq ft. (28.66 sq m)

Strut material: –

¾ inch EMT conduit ●

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3 foot 4 inch average length (101.6 cm)

Hub material: –

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Flange bolts ●

Grade 5 Zinc plated

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3/8 inch diameter

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1 ½ inch length

Flange nuts ●

Serrated zinc plated

Hub Test The L4 8v dome requires angle bends that are approximately 4 degrees. When climbing on the dome, certain areas popped in, some with very little pressure. Once collapsed, these hubs could still easily be climbed on, stood on, and jumped on without ill effect to the dome. When applying more force to some of the weaker hub sections, the hubs popping in created a kind of domino effect which caused parallel hubs to collapse inward as well. I did not measure the amount force required to pop in the hubs but have instead provided a map of the areas I thought to be weakest and strongest.

90 degrees

45 degrees

4 degrees

0 degrees

Core Triangle

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Hub Sections ●

There are 9 unique hub sections.

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Strongest

Weakest

Hub Test Map

Recap on Hub Sections Strut length is in alphabetical order. A is the shortest strut and K is the longest.

= Feet A: 3.03 B: 3.05

C: 3.13 D: 3.16 E: 3.16

F: 3.42 G: 3.44 H: 3.45

I: 3.51 J: 3.53 K: 3.53

Hub Test Overview For a dome (1/2 sphere) there are only six pentagons. Since this is a low profi le dome, there is only one pentagon (located at the topmost point). The pentagon hub section has only 5 struts to support it as opposed to the usual 6 struts on the hexagonal sections. Contrary to what I expected, the hub at the top of the dome was not the weakest hub and actually faired far better than several of the others

Hub Test Conclusion As more rows are added, the distance between base and top will increase. Since the middle section of the dome had the weakest hub connections and not the top, my biggest concern, if one were to build a complete L4 dome of 42 diameter, is the middle sections of the dome collapsing inward simply by the weight of the upper dome section. This area would also include the longest struts at 3 foot 7 inches (109.2 cm).

After testing each of type of hub connection, I attempted to pop in each hub of the dome. It required a bit of effort, though under conditions involving very heavy loads, large sections of hubs such as this will likely pop inward.

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