Geodesic Dome 2V/3V

[stud.magraf]

Hi All,

attention: long post! 😛

First of all I want to take the opportunity to reach out to @lars_christensen . I want to thank you for all the good resources you put out there, they're a great help!

To me: I am an electrical engineer from Germany with multiple interests and I always wanted to make things. Now my mind is not made to just make things, I need a tool that allows me to make what I want virtually and spit out plans with which I can make the actual thing. That's where Fusion comes in handy.

I spent the last couple of weeks in hospital and I took the chance to watch tons of videos, primarily of Lars, and started to get little things to work. I already made my own box with hinges and o-ring and stuff.

Now I have found something inspiring in the web and I want to put this into a param

Now if I am not too wrong this should be a Geodesic Dome 2V. The best resource for those I could find is this one: https://www.ziptiedomes.com/geodesic-dome-calculators/2v-geodesic-dome-calculator.htm . What this gives me is the dimensions of the triangles I need.

Here's what I would do:

1. Create a polygon with 12 corners on level 0 with the wanted diameter. Place it so that two corners are horizontal.

2. Create an offset plane at the height of the triangles 'A' and place another polygon on it with 12 corners.

3. Create an third offset plane above the second by the height of triangle 'B' and place a hexagon on it.

Questions:

1. Is the distance between ground level and level 1 correct?

2. Is the diameter of the second polygon correct?

3. What diameter and distance does the hexagon have?

4. How do I sketch the triangles? I have to connect the corners of the two polygons I made. Do I have to create another sketch in the origin XY plane and project the two polygons?

5. I don't want to use connectors, I want to screw each triangle to its neighbor. This will create several angles on the ends of each strut. I want to let Fusion create those angles while placing the struts. But how do I create the struts on the triangle sketches (do another sketch and project?) and how do I take care that the angles are cut?

I know I know. A long post from a newbie with a lot of questions ... I get to the point where I have placed the two polygons but because of my questions not farther. I will place screenshots as I try to follow along your answers (hopefully 🙂 ).

Thanks from Germany!

[TrippyLighting]

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@Anonymous wrote:
yes that looks fine!
i cant seem to see a download link but a360 is behaving weird right now. no
css formatting t all just plain vanilla html.

will check back later.
thanx

Lars

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I simply forgot to attach it 😉

It is attached now.

This is really just a solid body and I created it in Blender. Created is actually too big of a word as Blender has a pretty powerful primitive for Geodesic objects. I exported the mesh as .obj and then imported into Fusion 360 and converted the mesh to a BRep. 

[TrippyLighting]

As long as a geodesic v2 dome is built from triangles and based on an icosahedron it has 10 sides in all 5 symmetry planes. I am not sure you can built one from an icosahedron with 12 sides.

Mathematically precise and fully parametric. The only thing that I yet have to figure out is why it doesn't scale cleanly when I change diameter to drastically.

This is based on the Icosahedron tutorial I linked to in an earlier post and follows the same idea of creating and patterning geometry in place. 240 leaf components which is what is seen in the image above.

An Icosahedron is really a V1 geodesic dome. TO get to a v2, or v3 you simply have to divide the sides of the triangles in to two or three equal parts an then project those out to the circumscribing sphere. This is described well here.

[jasonhomrighaus]

Ok Finally got this figured!

The problem is you need to treat the triangles and the Pentagrams independently.  Once I broke each "Strut" into 2 separate pieces then you can make nice and clean in any size(Tested from 16" to 400").  

This one will scale at any level and you can adjust the dimensionality of the pieces.  Allows you to extract part totals and has 4 hidden sample pieces you can use to easily pull drawings and assign appearances.

Hope this helps someone was a pretty challenging puzzle but learned a lot about parametric modeling and working with dimensions and user parameters.  Also got to dig into formulas which are very much not intuitive.  IMHO that part of Fusion needs a lot of attention.

Let me know what you guys think

[TrippyLighting]

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@jasonhomrighaus wrote:

Ok Finally got this figured!

The problem is you need to treat the triangles and the Pentagrams independently.  

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Yes, in your design that is necessary because you are creating a half dome. Having to create half dome eliminates some of the patterning benefits you can get from creating a full dome.

Our initial construction method is very different because of this as well. I can start with a full Icosahedron and if I would stick with the edge length of the Icosahedron as the only parameter I'd need only one simple formula for the golden ratio. But the edge length can be calculated from the radius of the circumscribing sphere so I used 2 fairy simple formulae, which are both on the wikipedia site for the Icosahedron.

In any case, very nice work!

This method does not suffer form the problems one runs into when assembling individual components with joints. It's more work initially but scales much better.

I attached my model as well.

[jasonhomrighaus]

My formula stuff is a bit of a mess, i forgot to clean it up before I posted. there were several different attempts at things in there that don't get used.

I think if you Form the "Geo Triangle Big, outside board long" as a part of the "Geotrianglesmall" forming process it will fix your problem.  I had the same issue going on once I treated the small triangles separately from the large ones it fixed it right up.

The only thing i kind of don't like with this approach is that all the construction planes and sketches replicate(and bog down everything) with each iteration of the triangles.  I kind of like keeping those off board of the parts for this kind of item, then send the item into the patterning clean of baggage.  Obviously doing it this way for a complex project is much better.

[TrippyLighting]

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@jasonhomrighaus wrote:

I think if you Form the "Geo Triangle Big, outside board long" as a part of the "Geotrianglesmall" forming process it will fix your problem.

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Maybe, but I already  know what the problem is. There are different ways to do this, but this should note be happening. After I create the initial loft I offset a construction plan toward the center point of the "thing" and then split the top of the loft off.

When scaling too much up or down the offset direction flips and that should not be happening.

The thing is, if I play around with it enough it fixes itself.

@jeff_strater  @ryan.bales sorry for continuing to tag you with these things. It's gotten a little repetitive lately.  Can you please take a look at this ?

[Rickymediastudio]

I know this post is a bit old, so hopefully you still kinda remember how it was done. But what do I need to do to get this from a 2V dome into a 3V dome? 

[TrippyLighting]

If you read through the full thread, you’ll find some models for download. That should provide most of what you need.

Can you share your design so far?