Design of a better hub - domes and space frames

[Dx G]

I've had an ongoing project to make domes easier for people to make, assemble/erect and/or use.  One big issue has always been the compound angle, which is a problem for a lot of people, even those who build things. In particular, part of the endeavor is finding a design approach(s) that lends itself to using materials considered surplus, or even discard, which would otherwise end up in a land fill.

 
  General objectives are as follows for the hub:

1) Can accept a variable number of struts, often 5 or 6, but others as well.

2) A single design allows different face, axial and dihedral angles without requiring machining operations such as cutting, bending, drilling, etc.  That is, they are interchangeable without compromising strength and not risking structural failure.
  In addition, the part itself does not require precise angle and dimensional machining tolerances and is, to some extent, self adjusting.

3) Can be used with different strut materials (wood, metals, pvc, even bamboo, etc.)

 
4) Can be used with different strut shapes (hollow round pipe or tubing, round solid rod, square or rectangular cross section, etc.)

5) Hub can accept plain cut struts, where the ends do not require machining (drilling, compound angle cuts, etc.) and other customized modifications.  Nor do the struts require specialized ends or caps to be attached in order to join them properly.  This objective can be a real asset for something like bamboo, where the brute force approach of using lag bolts or even machine bolts are not good choices.
  In particular, the intention is to join parts in ways that strengthen the structure, rather than weakening the connections among structural elements.

 
6) The hub design also lends itself to use with panelized domes that require various face, axial and dihedral angles for proper assembly.

7) Does not require specialized materials or parts.
Ok, this one is part of my continuing rant.
 When I look at dome parts in the patent literature, and even in the market place, too many require complicated schemes that have to be made especially for that intended use, and aren't good for anything else. We see this even more now with the use of 3D printers. Often, this approach requires different parts for different domes, or even different hubs, so hubs or strut ends are not interchangeable and have to be custom made. Although the inventors may believe that this complexity protects them from being copied, the down side of that approach is that many such inventions go nowhere and quite a few are abandoned.
  For purposes of expanding the adoption of domes, IMHO it makes more sense to use materials that are commonly available, manufactured in large volumes for something else (PVC pipe, as an example) that will likely be around for a while, whether or not they are used for domes. This also helps keep the price down and availability up, unlike some of the wacky designs I see in some of the patents that would cost a fortune to fabricate and have little chance of ever being made in volumes that would make them more affordable.
  Thus, the motivation for this item 7, here in my list.

Sound like a tall order?  Well, as Henry Ford famously said, whether you think you can, or think you can't, you are probably right. As I usually tell myself, well, if you think you're so smart, why don't you do it? So I'm workin' on it.  

I invite discussion from anybody making any advances in this direction, or otherwise interested in the same.  

Dx G

[Robert Clark]

Dx G,

Thank you for taking the effort and time to detail the issues that should be addressed in a search for a hub design. I rewrote it in a little more concise form for my own better understanding.

"I've been working on a project to simplify dome construction and usage. One major challenge has been dealing with the complex angles involved, which can be daunting for many people, including builders. My goal is to develop a hub design that addresses several key objectives:

1. Flexibility: The hub should accommodate varying numbers of struts, typically 5 or 6, but it should work with other configurations as well.
2. Versatility: A single design should allow for different angles without needing special machining operations like cutting or bending. This ensures strength and structural integrity without precise machining tolerances.
3. Compatibility: The hub should work with different materials (wood, metal, PVC, bamboo, etc.) and shapes (round, square, rectangular) for the struts.
4. Ease of assembly: Struts should not require complex machining or specialized ends/caps for joining. This is especially important for materials like bamboo where traditional fasteners may not be suitable.
5. Strengthening connections: The design should reinforce the structure rather than weaken it at connection points.
6. Adaptability: The hub should also be suitable for panelized dome constructions that require various angles.
7. Accessibility: Avoid reliance on specialized materials or parts to keep costs down and increase availability.

Many existing dome designs in patents and the market are overly complex and require custom-made parts, limiting their practicality and adoption. By using readily available materials and standard manufacturing techniques, we can make domes more affordable and accessible.

This might seem like a daunting task, but as Henry Ford said, whether you believe you can or can't, you're probably right. I'm committed to working on this challenge and welcome input and collaboration from others interested in advancing dome construction."

The hub that can meet all these requirements is truly the sought-after holy grail of geodesic hub design. It would be the ultimate universal dome connector. However, I don't think there can ever be a "one-size-fits-all" hub design. This is simply because domes have so many different intended uses, sizes, and strength requirements. When designing a somewhat universal hub, we should consider these factors and then brainstorm for a solution for that narrowed-down set of requirements. I believe this will be more practical and achievable.

I'd like to share some pictures of a simple and unique hubless design by the group Ctrl+Z. They use recycled rough-sawn wood cut and assembled with simple tools. Many of you have probably already come across this on the internet. They call it the Brujodesica System. Here it is:

[Dx G]

Robert,

  Nice work.  There are certainly advantages to brevity, and you offer some wording which are improvements.  However, in some cases, there are some specifics I would prefer to retain for emphasis. 

For example, the best hub would accept "plain cut" struts.  Perhaps there is a better term, and in this case, this reference to the strut ends declares what the strut end *is* rather than what it *isn't* (i.e. lack of machining, etc.) .  The concept being that the strut end(s) can be used as it is found, such as from surplus or discard material, or, in other cases, as it would usually/conventionally be cut into pieces. I can't tell you how many job shops and machines are set up to cut right angles and are literally incapable of being use to cut any other angles in any plane.   The idea is that even nasty ends that may have been twisted apart could be used without any modification.

I will see what else I can learn about the Brujodesica System.  Initially, it appears to do what a lot of 

[Dx G]

 Sorry, got chopped off here, so completed below:

Robert,

  Nice work.  There are certainly advantages to brevity, and you offer some wording which are improvements.  However, in some cases, there are some specifics I would prefer to retain for emphasis. 

For example, the best hub would accept "plain cut" struts (my item 5)

Perhaps there is a better term, and in this case, this reference to the strut ends declares what the strut end *is* rather than what it *isn't* (i.e. (your item 4, lack of machining, etc.) .  The concept being that the strut end(s) can be used as it is found, such as from surplus or discard material, or, in other cases, as it would usually/conventionally be cut into pieces. I can't tell you how many job shops and machines I've seen,  set up to cut right angles and are literally incapable of being use to cut any other angles in any plane, much less a compound angle.   The idea is that even nasty ends that may have been twisted apart could be used without any modification if sufficiently straight and free of other disqualifying defects. 

I will see what else I can learn about the Brujodesica System.  Initially, it appears to do what a lot of hubs I've seen do - they enjoy simplicity, but give up some strength and logistic issues. Without shims and an array of careful cuts, I can imagine some troublesome faults.  I will see if that is simply a result of and understanding gap on my part. 

In any case, I am grateful for your review, comments and interest.  I believe the holy grail is more within reach than most people believe.  I intend to stay on the trail to the grail.   :-)

Dx G

[Paul Kranz]

Dx G: Maybe instead of a universal hub you could go with a universal hub maker. Inputs would be the class and frequency and the output would be the hubs required. A sort of 3-D hub printer. Paul sends...

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[Robert Clark]

Is there a way to gather and consolidate in table form dome data on the following:

1. Most common use for a dome.  It'd be nice to see the different uses listed and a percentage.
2. Most common size. Same thing as above with percentage for different sizes.
3. If geodesic, then what is the most common frequency?  Again, percentages in table or graph form.
4. What is the most common type of covering? ( I guess this depends on the intended use )

Also, I'd like to see a comparison list of common strut materials and their advantages and disadvantages, ease and difficulty.

[Dx G]

Thanks guys.

Robert - yes, I can see the value of looking at the data. However, keep in mind that those numbers come from our *current* system of making hubs.  We would have to reflect on how the selection of what domes, spaceframes or other structures we build would change if some of our current constraints were lifted.

Paul,

 A good thought, thanks for sharing that.  Not my intention to be negative or critical, but a few follow up points meant to help clarify what I'm chasing. 

(Note, I may be misleading readers somewhat by using the term "hub". 

   A hub congers the thought of one piece of hardware (like some plate) that you'd use to plug struts into.  So perhaps I need to use a different term.  The real key is how to join struts, perhaps without the use of one physical hub object.  If you look at Hoberman Spheres, you can see one such example of how frame elements can be joined, although I recognize it doesn't meet the criteria I've laid out. )  NASA has also looked at this on and off for years as well.

   So, I'll start calling it a connector, instead of a hub.

1) The user would need such a device (the 3D printer type machine)  for this to work.  With the other approach, they would just need the connectors, which would, theoretically, attach/connect "any" struts.  Also, that device needs inputs (power, fabrication material, etc.), things some locations may not have, especially disaster areas trying to get housing up fast.  Those folks might make better use of a shipping container full of connectors (and they are all the same). 

2) Recycle and carbon footprint issues

Sure, a device that can make this hub or that hub. That really works very well in a lot of settings. However, it also proliferates hub types. Once you make a 5 strut hub, you can't use it as a 6 strut hub.  The other approach does not have that constraint, since that connector works with "any" strut or strut assembly. 

    One of the things this offers is reduced waste. It would be possible to reuse the connectors from one dome and use them for another. Whether a dome came down from storm damage, intentional demolition or other circumstances, it would be theoretically possible to reuse the connectors, if still intact, even in an entirely different dome. For example, taking them from a dome based on an icosahedron and using them to erect an octahedral.  That is, once we have invested materials and energy fabricating these connectors, I can see where they may have a longer life, and be a better long term investment that making all these different hubs.  

    Further, one would have to look at the materials and energy it takes to make the device, the input materials, and then support its use in the production of hubs (gotta plug it in some place).  This would have to be compared to the same inputs, and production equipment, required to make the connectors themselves.   In the case of the device, you do have a choice of shipping the machine and input materials to the construction location (decentralized logistics), or just sending the required hubs.  Less likely you would have the decentralized option with the connectors.   In addition, if the connectors really were all the same, there is a certain economy of scale in making large volumes of a single item, so hopefully automation would reduce the cost.   The jury is still out on which approach has more such advantages. 

Partly I post this to help inspire others to consider the possibilities and think about the issues.  I think it is likely that the brain trust will come up with ideas I do not or would not have.  So even if success is beyond my own grasp, then someone else will have longer reach.  The real key is that the existence of such a connector/system could be a true inflexion point in the adoption of domes, and perhaps make better use of surplus and discard materials that are piling up in our landfills.

Dx G

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[Paul Kranz]

Robert:

Based upon https://www.airbnb.com/category_tag=Tag%3A8173 I can offer these observations:

1. Most common use for a dome.  It'd be nice to see the different uses listed and a percentage.

Dwellings are the No. 1 application

2. Most common size. Same thing as above with percentage for different sizes.

No. 1 size is 24' in diameter.

3. If geodesic, then what is the most common frequency?  Again, percentages in table or graph form.

No. 1 frequency is Class III, 3, but Kruschke.

4. What is the most common type of covering? ( I guess this depends on the intended use )

No. 1 covering is skin over hub n' strut.

Paul sends...

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[Paul Kranz]

Make that https://www.airbnb.com/?category_tag=Tag%3A8173.

[Dx G]

  I had an exchange with one of our dome enthusiasts, and an additional benefit of, what I prefer to call it, a universal strut connector. I repeat this (paraphrased) below.

Actually one of the advantages of a dome is that you can build a large structure from short materials that others can't use and would discard as "waste".  The smaller parts are also easier to transport, ship, package, store and work with.  Although a large, high frequency dome may require a variety of strut lengths,  I don't think this is as big a problem as the proliferation of hub types needed, due to the variation in axial, face and dihedral angles.  So if you could use the same connector in the whole dome, even in a very high frequency dome, and all you needed for struts were groups of various lengths one could just chop off square with no special ends or installation of any special caps, I think this would be a lot easier to live with.  In particular, this would invite more use of things like cut bamboo poles, which people fuss a great deal with, trying to come up with ways to connect them. This improved connectivity would even be true for ellipticals, octahedrals, and other such domes that are not used much now.  I don't think the struts are the main issue, I think its the hubs and the strut ends that generate the bulk of the unwanted complexity.  Chopping struts off at any given length, in any number, is pretty easy, and can be automated or otherwise mass produced.  If that complexity is reduced/eliminated, I think the door of opportunity for domes opens much wider.

Dx G

[Paul Kranz]

Dx G:

I agree. The struts and what they are made out of are secondary. They only serve to push the connectors away from each other in tension.

A universal connector (Uniconn?) would have to account for the two dimensions of the struts, let's call them "horizontal" and "vertical" movement. Horizontal movement is the lateral placement of the struts equidistant on a plane and vertical movement accounts for the up-and-down movement. I have had success using loose-pin hinges for the 1-dimensional horizontal movement (attached) but not both horizontal and vertical.

I theorize that a ring would accommodate both dimensions. Thread the ends of the struts onto a ring. If the struts are cut to the correct length, tension would stabilize the ring as it would "automatically'' force the  horizontal placement of the struts relative to each other and set the vertical placement of the struts relative to the circumsphere, although I have never applied the scientific method to the theory.

Then the questions become, "How big to make the ring?" and "What to make it out of?"

Paul sends...  

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/204b27c7-3dfb-4ba9-b3fe-b1fb1e287f81n%40googlegroups.com.

--

Very high regards,

 

Paul C. Kranz, LMFT

Kranz & Associates, LLC

ReviveTheFlame.com

[Dx G]

Paul,

  Good thought, but if we were to be purists, we are back to my rant.  That is, having some custom ring made that only works for this purpose, unless there is one out there for sale that is made in large volumes, hopefully at low cost, for something else that would be around for some time.   Could be the concept the ring represents could be implemented in a way that satisfies the off-the-shelf issue.

  Consider this.  A conventional hinge is designed to work in one plane. So what about an unconventional hinge...

Dx G 

[Paul Kranz]

Dx G: The ring will probably give you what you want. I will test with popsicle sticks and binder rings to see how stable the structure is. Details coming... Paul sends...

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[HUX METAL WORKS]

Hey guys I  love these domes I have built one out of pvc 16ft diameter I'm having a hard time getting it covered I have tried everything and it just doesn't look good can anyone help I would greatly appreciate it I am new to this but in willing to learn I have bought several plans  but to me the math is overwhelming I would like to know one  more thing can anyone give me any ideas on  connectors I heated and bent it on the pvc dome I mentioned earlier  and it was a pain anyone's help to get me to where I can understand this stuff I'm trying to make one for me and my wife to have to get out of the weather but still be able to enjoy the outdoors together  I appreciate all the help I can get  Tim  thanks 

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/cbbe9757-41e3-418b-9455-bc16e8a4b0bdn%40googlegroups.com.

[Paul Kranz]

Tim: Are you wanting to address the cover or the connector first? Paul sends...

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/CANj1HfD35HHP4EEdszzUHNjKgNWeccPYKTZ2kAQKNBi%2B4JqG2Q%40mail.gmail.com.

[Dx G]

If you are looking for some good materials and ideas on how to cover a dome, just do a web search on "covering a geodesic dome" and you will find dozens of sites and youtube videos which will be real helpful.  If you don't get what you need from that, post again and we can always send you some suggestions.

Dx G

[Paul Kranz]

Tim:

You may want to try buying a manufactured dome cover and then building your own dome for it to the manufacturer's specs.

Take a look at all the Airbnb domes for ideas on what covers are available: https://www.airbnb.com/?category_tag=Tag%3A8173

Stay tuned to this thread for my experiments on a 2-dimensional connector.

Paul sends...

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/36690209-c6b5-48b6-96bb-aac69ef459cfn%40googlegroups.com.

[Paul Kranz]

Here's my experiment: https://photos.app.goo.gl/zVhgaXdujkZJttPG6

Paul sends...

[Robert Clark]

Paul,

I like the simplicity.  I modeled it up real quick to better visualize the concept. The hole will be just slightly larger than the ring width.  The hole through the strut is a cylinder that will be riding along the surface of a torus. You would need to address an effective method for getting a closed ring through the holes of the struts.

[Adam]

https://www.wangerflange.com
I think these are a superb solution for geodesics. Lots of applications.

[Eric Marceau]

Not completely sure where you are going with that design.   So, some questions ...

Material selection:

• Plastic
• Aluminum
• Steel (carbon)
• Steel (stainless)
• Titanium

Component Assembly method:

• Injection-moulded assembly (2-step)
• Hand-forged
• Press-forged

Structure Assembly method:

• Flat bar bolted in strut slot
• Flat bar snap-locked in strut slot (cotter-pinned)
• Flat bar snap-locked in strut slot (blind rivet)

Or are my questions premature?

Eric

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/3f3a60d5-2794-490f-9332-79f759e57d23n%40googlegroups.com.

[HUX METAL WORKS]

Great I have looked all over but I don't know where to find them any advice would be greatly appreciated I have even talked to some tent manufacturer but everyone wants me to by domes from them thanks for sharing your information. Tim 

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/CAE1FiLXULqvkxmgW%2B1uZSBSpWn-T1rySF93B4BN4DqHB9R%3DXVA%40mail.gmail.com.

[Eric Marceau]

Is the intent to have multiple "flats", one for each strut?

Eric

On 2024-02-20 15:40, Robert Clark wrote:

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[Eric Marceau]

re  "Wanger Flanges" ...

I think their configuration seems OK for 6-strut joints, but not for 5-strut joints, because you would need to offset the connectors that are joining by the same amount.  So, that leaves one connection with a flange on bottom and flange on top attempting a bolted joint, leading to a "misalignment", if we talk about being "theoretically true".

Functionally, for smaller structures, I think they would be practical and workable, leaving the choice of strut material entirely up to the builder.  

For wood struts, I would reinforce the anchor end with a kind of threaded pipe clamp, or maybe just a solid sleeve adjusted to the strut diameter.

Eric

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/67c98cd4-8d2c-432c-bb8d-ccb8b31092fen%40googlegroups.com.

[Robert Clark]

Again, what size domes are these intended for?  Personally, when I imagine a universal connector, I am thinking of domes in the range of 10 to 24 feet in diameter.  My job is a mechanical designer.  In my free time I have designed my own version of a universal hub connector.  It would not have off the shelf components.  It would be a hub consisting of injection molded polypropylene parts.  There would be just three unique parts that could be created in simple 2-part molds without the need for complicated side actions.  Only if these parts could be mass-produced in the tens of thousands, would the price come down to perhaps five dollars a hub.

[Eric Marceau]

To clarify my intent,

The 2-step injection-moulded assembly would be

Step 1 - mould the ring

            During this step, it is conceivable that the process might have an additional step
            (to minimize future "welding wear" from plastic on plastic rubbing under pressure)
            by having the mould position tubular sleeves, at those location on the mould cavity,
            corresponding to eventual alignment of the 5-strut/6-strut configurations.

Step 2 - place ring in another mould where it is held suspended
            while plastic injected around the ring for the size of the flat bar.

Alternate approach is forged and polished stainless steel ring used for step 2 above.
If using this approach, need to "pre-heat" rings for placement in the mould to match
the operating temperature of the mould to prevent repeated stress fracture of mould cavity elements.

Just food for thought,

Eric

[Robert Clark]

Domes require hundreds of connector parts, preferably all identical.  Hence, the search for the "universal" connector.  Parts need to be produced in mass.  Injection molding is one of industries fastest and cost effective ways to produce parts.  But, If parts have to be manually removed from one mold and placed into another, it will slow the production down considerably and drive up the cost per part.

[Eric Marceau]

Is it safe to say that the connector design may also be dependant on the relative size of the connector?

Can it be said that connectors on higher-frequency domes don't need to be as strong as those of a lower-frequency dome of the same overall size?

Dome A at 4𝜈

Connectors at equator  =  4 x 5 = 20
Guiding ratio of Load per connector proportional to      L / 20    or    L / √20

Dome B at 8𝜈

Connectors at equator  =  8 x 5 = 40
Guiding ratio of Load per connector proportional to      L / 40    or    L / √40

Would defining such a relationship or sizing "curve" be desirable / beneficial / possible ?

Eric

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/fb546072-661b-4d70-b329-e29bf613aa2an%40googlegroups.com.

[Eric Marceau]

The only way to form a closed ring ... is to have 2 half-circles join.

I can't think of any way to join those 2 half-circles that would not end in a weakened ring.

Attempting to come up with 

• some kind of external screw-tube would be a mis-fit,
• some kind of flanged coupling would be a mis-fit,
• welding 2 halves on site would be time consuming and (my opinion) a poor choice of method.

So ... 

• we must assume that the ring must be solid ... 
• and figure out a way for the flat bars to wrap around the ring without those losing much strength.

Similar to the issues for half-circles, half-bars coming together are only as strong as the "bolting" technique used to hold them together.

So ...

• it is suggested that we cannot depend on split parts ...
• and consider a single solid part, such as a hooked form,
  where the hook latches on (snap-on?) to the ring.
  

More food for thought.

Eric

On 2024-02-20 15:40, Robert Clark wrote:

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/3f3a60d5-2794-490f-9332-79f759e57d23n%40googlegroups.com.

[Dx G]

Glad to see the discussion and thinking about this, and sure don't want to throw a wet towel on anything. However, as we look at approaches, questions come to mind we should consider as the thought process proceeds:

Wanger flanges are terrific.  How does one use them with hollow tubing or anything that won't take attachment directly into a strut end?

For all of these:
 - Some hubs would be in compression (strut ends pushing into each other), others in tension (strut ends pulling apart).  Further, those forces are not symmetrical in many cases, as the are encircled by different triangles with different strut lengths. So what happens with some of these approaches when those forces are high, and hub distortion, twisting, deformation or outright breakage/failure approaches immanent?
 - How would one ever expect to see the volume of units made get high enough to command an attractive price?
 - What does one run into when one uses materials like bamboo?  Can we find a solution to such issues for any of these approaches?

The rule is, don't discard what's good because its not perfect, but perfect is a good goal to strive for...

Dx G

[Dx G]

Tim,

 As I suggested earlier, if you run some internet searches, you will find all kinds of dome calculators (that do the math for you) and information about making your own covers or buying covers.  A few examples here, but there are lots more.

 Maybe these will get you started
https://www.domerama.com/calculators/cover-templates-for-3v-59-geodesic-dome/

https://www.ziptiedomes.com/geodesic-dome-calculators/geodesic-dome-calculator-index.htm

Dx G

[Gerry in Quebec]

Hi Dx G, Tim & others,

Good discussion on hubs.

But please note the problem with the Domerama page & PDF file to which Dx G referred. The key error is described here:

https://groups.google.com/g/geodesichelp/c/um9FG58AVjE/m/rtxgB6XKAgAJ 

- Gerry in Québec

[Dx G]

Thanks for the tip off Gerry.  I sure do see a lot of sites with the info Tim wants, but haven't used them to the point of verifying their performance.

Dx G

[Paul Kranz]

Ring & Popsicle Sticks: Octahedron: https://photos.app.goo.gl/gQ1nbd9G5Bowm7689

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/190dd38c-ac0e-4ee3-920b-7d2f8bd41557n%40googlegroups.com.

[Dx G]

Good progress.  So if you grab the popsicle sticks and try to move them, what happens?  If you press down on a hub or squeeze the structure, what happens?  Sure I get that this is just a model, but what I'm wondering is what happens if this is put under stresses, as a structure has to tolerate, especially nonsymmetrical ones like high winds, perhaps with wet snow, from one direction.   If it flexes a lot, this could be good for somethings but really bad for others, like interior sheetrock. 

   One example that might possibly improve stability occurs to me.  If you had a series of washers, or a spacer, on the ring to keep the sticks where they are on the ring, does this improve stability.  No, I'm not a real fan of adding more and more components, but this kind of thing sometimes helps point us to something that will work that escapes some of the down sides.

Dx G

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[Paul Kranz]

Dx G: There is some rotation around the ring. When I applied pressure to the top of the tetra, the struts from the top spread out and touched the surface that the structure was sitting on. From there there is no movement horizontally or vertically. I will apply those two dimensional stresses to the octa and send a video. Paul sends...

[Dx G]

Paul,

  That's a good start.  Often what it pays to do is look at the parts when the structure deforms.  Typically parts will either move closer together, spread further apart, rotate, bend, etc.  If we don't want them to move, one can consider options.  If they move further apart, even a cable with sufficient tensile strength can help. If they are moving together, a brace or block can help.  Some things like concrete do a great job resisting compression but can be a disaster if put in tension.   

    Anything can be over done of course, but this can help shoring up a weak design, or suggest an improved design that will eliminate the need for supplementary reinforcement. 

Dx G

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[Paul Kranz]

Dx G: It turns out there is nothing to show. I can't get the octa to budge. Paul sends...

[Dx G]

That's a good sign.  So let's say it passes an initial hurdle.  A further step would be to make a polyhedron with a larger axial and dihedral angles.  Its those shallow hubs that tend to buckle, especially when they are not symmetric.   Small axial angles are always strong and hard to collapse, but most shell structures have larger axial angles. 

Dx G

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[Paul Kranz]

Dx G: Icosa is next. Paul sends...

[Paul Kranz]

Dx G: Here is the Icosa: https://photos.app.goo.gl/TMi7LV5ZCTPXWE8d7. The last ring was murder! Closing the last ring was much more difficult than the octa. There is a little giggle around the rings. Snapping the struts onto a solid ring would be a whole lot easier. Paul sends...

[Paul Kranz]

Dx G: The problem with closing the last ring in the icosa was that the ring was too small to join 5 double-thick popsicle sticks. So, you'd have to go even bigger for a ring to join 6 which would probably be the max.

Regarding the giggle at the ring. It could be stabilized by either driving a screw through the strut to create friction on the ring or by whatever you use for covering the triangles. 12 years ago I built a greenhouse out of a 1-freq icosa using Star Plates® and created inserts to fit inside the triangles which turned the icosa into a super structure. Paul sends...

[Eric Marceau]

Hi Dx G,

On your point

Wanger flanges are terrific.  How does one use them with hollow tubing or
anything that won't take attachment directly into a strut end?

I believe you need to consider approaches similar (see attached) to what is used for 

• various Cable Television cable connector attachments;
• industrial hydraulic hose connector attachments; or
• plumbing hose connector attachments.

Those approaches all use an approach of

• sliding on an external (optional-threaded) sleeve
• inserting an internal anchoring/attachment connecting component, then
• applying a method to "fasten" those together, whether by crimping, or screwing, or pressure-inserted into inner diameter of the receiving strut.

Some food for thought.

Eric

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[Dx G]

Eric,

  I agree, there are lots of "connectors" out there in all kinds of industries and uses.   Not a bad place to start, but ultimately, the real key is having a *structural* connector, that can accommodate building materials used for struts, and stand the stresses imposed by a building exposed to loads (wind, snow, etc.)  Then there are the other items on my original list to consider. The key point is closing the gap between what *could* work and what *would* work.  That's the missing piece...

Dx G

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[Dx G]

Paul, 

 Interesting foray into the fray.  Sure, go with a bigger ring, or reduce the mass of strut which is "in the way", that is, without undesirably weakening the connection.  No silver bullet occurs to me at this point, especially when you look at my earlier "list" of items/features.   I'm also thinking, how do we get the advantages of what the ring-based system offers...without the need for a ring?

Dx G

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[Ashok Mathur]

They are premature as they are presently just feasibility models.

They will need refinement. Wait till a 3v diameter dome gets built.

I have long admired Wagner joins but there is no way to produce them in small numbers in India?

Is there a simple way to make make of stainless steel sheets with just one or two bangs?

Regards

Ashok

Sent from my iPhone

On 21-Feb-2024, at 2:58 AM, Eric Marceau <eajma...@gmail.com> wrote:



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[Eric Marceau]

Hi again,

On your point of what could work, if the connector types they use for industrial hydraulics work as good as they do for the pressures they operate under, I firmly believe an adaptation of those designs would be valid for consideration for designing structural joints under tension.

As I said before, food for thought by joint designers. 🙂

Eric

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[Eric Marceau]

Hi Ashok,

You are referring to a "progressive stamping die", using a continuous strip of metal.

This URL

https://www.esict.com/blog/how-are-parts-made-using-progressive-die-stamping/

shows an image of a strip that displays 

• the gradual punching of holes (2 patterns; 3 holes on small arc; 3 holes on larger arc), and 
• outline cutting (3 stations; inner opening of smaller piece; outline of smaller piece ; outline of larger piece)

For the "Wanger Flange", you could design a die that would have stations 

• punching the holes, then
• punch the outline of the piece to fold, then
• fold the one tab, then
• punch the cutout of the final piece.

It is possible that you would need to combine the 3rd and 4th step into one, but I have no direct experience in designing that kind of progressive die.  The trouble with those kinds of dies is the difficulties in getting the alignments right.

The alternative, given the realive simplicity of the part, is 2 separate molds to handle pre-cut paralellograms.

• One die for punching the holes, and 
• the other die to both cut and fold the angle, a dual-action from one continuous downward motion.

The trick with the latter die is to not have the parts stuck in the die between operations!  Tool designers have tricks to kick the parts clear of the die after such operations.

Hope that helps! 🙂

Eric

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[Dx G]

Eric,

 In principle, I whole heartedly agree.  Those couplings *could* work. After that, it becomes a matter of critical details. As to whether they *would* work...hydraulic couplings are designed to resist "internal* pressures that would have a tendency to leak or burst from inside.  Likewise, the rubber and flexible hose used in hydraulics have the same spec.  However, the forces applied to a strut/hub connection tend to be compression, tension, bending/twisting etc. forces from outside the part.  

   So if I take the liberty to extend your thought, it might make sense to look at structural couplings already designed for the expected stresses,  like those used to connect tent or flag poles, space frames, etc.  Certainly, if items like hydraulic couplings offer features we don't see in existing structural connectors, then this is surely a worthwhile exercise, in looking for useful "adaptation".    

    Not trying to discourage anything.  Just looking (or groping, as the case may be) to span that space between what *could* work and what *would* work...

Dx G

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[Eric Marceau]

Hi again, Dx G,

Understand that I am not invested in the idea of using a "hydraulics-based" solution.

However, you may not be aware of the pressures/forces being used in those joints.

If we consider the SAE 100R2 standard, 

• the Maximum operating pressure is 5000 psi, but 
• the minimum burst-pressure is 20,000 psi!

If we take a conservative view, lets limit ourselves to a rating that I've seen many times for tubing connectors, namely 3500 psi (241 bar).  

For a 1" internal diameter, that translates to an 0.78 sq. in. area, which represents about 2700 pounds of tension.  That is some strong connector-retaining resistance force!  ... All derived from a crimp fitting!

My gut says that the structures that you are considering potentially would not encounter forces reaching higher than about 1/4 to 1/3 of that number ... and that being tension-wise (compression is a minor consideration for that type of joint design).

I can't help but think that there is something there that could be applied to tubing/pipe in the dome design/construction context.

Does that help put the potential of concept into perspective regarding a workable adaptation?

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[Eric Marceau]

One last contribution for the universal connector idea.

For those willing to pursue that route, McGill University used to offer a final-year (4th) course in Value Engineering, where people from industry would put forward a concept design and a team of students would revisit, rethink, modify, optimize and finalize a revised design maximizing the performance per design criteria.

Apparently, they still do:

https://www.mcgill.ca/ve/description

Many Universities have such an offering, for those who are interested.

Eric

[Dx G]

Eric,

 Sure, I get the reasoning and appreciate the numerical considerations.  I'll see if I can dig up some related numbers for actual structures to see what those ballpark figures forces look like.  If you are looking at tension, consider high tension wire used in fence construction.  The higher capacity stuff is 200,000 psi., only a few cents a foot, and widely available.   Great stuff for something like a yurt, and some domes, that need a "waist band" of high tensile strength.  Also consider that fluid couplings must be leak free, so may have constraints in their design that would not apply to our use. The key would be making some good use of the design (the crimp?) found in the hydraulic coupling that delivers tension resistance to the structural connector.

  So even if we establish that a crimp deserves consideration, lets look at the next increment in development.  Consider also that many, or most of the dome hubs are in compression, rather than tension.  An important issue.  We would have to look at how well that design (crimp?) handles compression, bending, twisting.  If one wants to use the same connector for all joints, the design has to accommodate them all.

 Dx G

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[Eric Marceau]

... and here I thought that, given the application of industrial hydraulics for cranes, tractors, oil drills, shovels and harvesters, those  would cover the twist/bend conditions handsomely, with the compression one being a given where the outer compression sleeve would be long enough to ensure that lateral stability.

Go figure!

Also, your original posting, and Roberts "re-statement of those requirements", did not seem to suggest tensegrity, but your last response does.  I am a bit confused by that "shift", but I don't think it precludes the crimp-style connectors.

Eric

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[Dx G]

Eric,

  Actually you are quite right.  Clearly, I did not specifically state in my list that the connector needed to successfully operate in compression, tension, torsional and other forces.  I can see that I need to add that, and appreciate your mentioning this. So, no, its not a shift, it was an oversight which, having been alerted, can address.   This addition will improve the spec list for the holy grail connector.

 With respect to hydraulics, there is an entire industry that supplies parts and equipment to protect hydraulic couplings and lines, even metal ones, from the very forces imposed on the equipment by its intended use.  Hydraulic fluid is under high pressure and usually very hot in operation, so even a pinhole leak can behave like a hot drill bit, and punch a nasty hole on anything soft, such as the human body.  It's darn dangerous and the topic of a lot of safety training.  A lot of design goes into isolating hydraulic lines from mechanical stresses, just as you would electric lines.   Its one of those things most people wouldn't know unless properly trained to work around machinery.  A case of what you don't know can hurt you, or even kill you...

Dx G

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[Eric Marceau]

Hi Dx G,

I am somewhat baffled by your discussion about the safety issues regarding industrial hydraulics.

I do hope you understand that it was never my intention to suggest that a Geodesic Structure become one sustained by internal pressurized hoses/tubing/piping!

I was strictly limiting myself to the physical/mechanical configuration of the crimp-based connectors that are used by that industry as a reference point for design ideas on the physical design of that universal connector ... never extending that into the idea of considering high-pressure systems as a basis for structural tensionning/stabilization.

I hope that clears up any possible confusion that may have arisen.

So ... in simple terms ... no hydraulics-based design!

Eric

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[Dx G]

Tim,

  Ran across this and thought of you.  Several dome posts on his site, some may give you some ideas.  There is more out there like this.

https://northernhomestead.com/covering-the-geodome-greenhouse/

Dx G

[Dx G]

Tim,

  Another thought to share.  I don't know if you do "metal works" per se, but if you do, and you are interested in domes, I'd suggest you look at patent 5165207 by Harlan Oehlke.  One could make these to go inside or outside tubing, could be stepped to accommodate different size tubing and/or make the sleeve to take different shapes (even things like square cut 2x4s).  Having these available in the marketplace would probably increase the number of people choosing them. 

  If you start making and selling them, I might be interested in buying some if they are affordable.  I suspect I'm not the only one, but that is, of course, a marketing and business decision. 

Dx G

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[HUX METAL WORKS]

Can you tell me how to find them I would like to see what you are talking about thanks for sharing your experience with me  Tim 

[Eric Marceau]

Dx G encouraged me to share this, given the current discussion of asymmetric loading.

For those who are interested, the attached is a Masters Thesis, published in 1984.

GEODESIC DOME ANALYSIS
by William Floyd Shirley
University of Arizona

ABSTRACT

Results of physical testing and analytical studies are presented
for two geodesic domes. The domes are of the Pease panel dome variety
with different diameters. Deflection distributions are reported for
domes having symmetrically and asymmetrically applied uniform loads.

The development of geodesic domes is discussed with particular
attention paid to the calculation of chord factors. Information
regarding the development of domes from various polyhedra is also
included.

Analytical studies concentrate on the evaluation of conventional
finite element models. Beam, bar, and trim elements are used in various
combinations to model the structure. Application of various modified
shell analyses are also included.

It is concluded that Pease panel domes, if adequately pre-loaded,
can be modelled using pinned-end beam elements or trim elements. The
load distribution behaviour of the domes, in regard to truss or membrane
action, is also discussed.

Two separate cases built and tested.

Case I - 39-foot wooden truncated dome

This test examines deflection over time.

Page 49 of the PDF (p. 33 of the thesis) gives an outline of the loading performed and what, where and how loads were being measured.

Deflection over time (it is creeping) and recovery (over time) for the wooden structures if provided on page 54 o the PDF.

Case II - 45-foot wooden truncated domes

This test examines assymetric loading and resulting deflections.

Loading is performed by both symmetric and asymmetric layout of sandbags over panels to loading (snow, wind).

Page 66 is deflections for side A.

• Only Side A loaded
• Side A & B loaded

Page 67 is deflections for side B:

• Side B not loaded
• Side A & B loaded

Eric

[Dx G]

Tim, 

 See if this works for you.

https://patentimages.storage.googleapis.com/3d/53/ab/6ab972e14d8019/US5165207.pdf

If that doesn't do it, let me know as there are other ways to skin the cat.

Dx G

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[Eric Marceau]

Hey Robert,

Very good concept, but how do you fix the parts in the assembled joint.

All I am seeing is movable parts ... and no attachment to the struts.

Would you be suggesting the use of high-voltage current to "weld" the hook tabs to the inner wall of the pipes/struts?  (ring for one welding pole, pipe for the other?  Also, how to do that and ensure uniform weld for all 4 linear contact points of the "cross" joint that is inserted into the pipes/struts?

Eric

On 2024-02-28 15:20, Robert Clark wrote:

Everyone is after a universal dome connector. I had time this afternoon and modeled up one in SolidWorks. It's not completely universal but could be used in a lot of dome designs.  The center hub is made from a short segment of 2 inch nominal schedule 80 steel pipe.  the other pieces are laser/plasma/waterjet cut from 1/8 inch plate steel. The struts are 1 inch nominal PVC pipe. It's not off the shelf items. It's not found material.  So, it's probably not what you guys are after.  This is so simple and straight forward that i wouldn't doubt there's already a patent.  I just haven't looked or have the time.

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[Robert Clark]

Eric,

The parts that go into the tube would be a tight press fit.  Perhaps they would have a serrated edge for better grip.  If necessary, it could be designed with a hole through the tube and the part to insert a bolt.  This is not a finished design by any means.  I thought of it this afternoon during down time at work and modeled it up in a half hour.  It's more conceptual at this point.

Robert

[Eric Marceau]

Has anyone come across studies on magnitude of load for the effective tension failure as applied to various threads sizes, and depending on 100% thread circumference , vs 80%, vs 15% (approx, thread contact for Gerry's cross-point connector hook, if threaded into pipes), and whether that's a linear (or non-linear) relationship with the proportion of thread vs full thread?

Wondering to what extent the less-than-full-circumference has an impact on the strength of the tread profile (contact surface, shear section, etc.).

Eric

[Dx G]

Eric,

  Unsure what you refer to by Thread sizes.  Is this bolt thread, or some wire inside the struts?   Common high tensile fence wire is 200,000 psi tensile.  Having trouble picturing the assembly you are asking about.

Dx G

[Eric Marceau]

Sorry, Dx G,

Imagine grinding a slot of 1/8" on a 1/2 " down the center of the thread on the bolt end.

Rotate the bolt 90 degrees, and grind another slot.

That leaves you with approx.  50% of the thread on 4 thread segments.

Does that help?

Eric

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[Dx G]

Eric,

 I think I can imagine what you describe. Basically a cross hair pair of slots at 90 degrees, starting where one would normally start a nut on the bolt.  If you ever come across a drawing of that, post it for us.  Can't say I've seen any data on reduced thread in that fashion, but I'll watch for it.

Looks like you can estimate the affect of losing thread in general, by adjusting some of the variables. Not sure its valid, but worth review.

https://www.engineeringtoolbox.com/bolt-threads-stress-d_856.html

Dx G

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[Eric Marceau]

Also, making reference to Roberts concept of interlocking bars and comparing to my recent visualization model, the thread will not fail by internal bending collapse, given the rigid backing of the bars covering the full Internal Diameter.

So failure would be strictly from shear on the thread across the midpoint of the threads (assuming pipe and bars have same material composition) or the diameter where the shear strength x thread section area  balances out to the same value for the two components, pipe and threaded connector.

I do feel, however, that partial threads would be weaker than full-circumference threads, when comparing on a fractional basis, because the segment ends would tend to have more of a bending effect than if we were dealing with full threads, leading to a lesser resistance to failure (at least that is what my gut tells me 🙂).

Eric

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[Ashok Mathur]

Dear Eric

I can reduce my case to three sentences:

1. Compressive forces can be applied asymmetrically

 to any tensgrity structure.

2. Instantly, if the structure does not break,

as in an explosion, tensional forces will react and

 neutralise the asymmetric compressive load 

with a uniform tensional reaction.

3 Effectively the assymetric compressive  forces 

will be fully neutralised even if uneven snow lies on the dome for 3 months.

Regards

Ashok

Sent from my iPhone

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[Ashok Mathur]



[Dick Fischbeck]

Well put!

[Eric Marceau]

So, Ashok,

Your concept is
        one of tensegrity (tension wires),
not
        one of struts using connectors for positioning/fastening/retention.

I was under the impression that the discussion on connector was focused on the latter.

Was I wrong?

Eric

On 2024-02-29 08:05, Ashok Mathur wrote:



 Dear Eric

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[Eric Marceau]

Hey Dick,

Again, I might be wrong, but I don't think the tensegrity approach was in Robert's mind when he conceived the model for the connector design that he offered to the group.

Robert, am I wrong?

Eric

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[Robert Clark]

Eric,

You are correct. It is just a hub design for a standard geodesic dome. Not a tensegrity structure.  Geodesic structures do have a combination of tensile and compressive loads.  

The hub I designed can handle varying angles side to side around the circumference of the hub. And, it can handle limited angles up and down to accommodate various frequency domes.  The concept is of a hub connector that can be used at any vertices of a geodesic dome from 3-frequency and upwards. The struts would be cut to different lengths, but the hubs would all be the same parts.  The limiting factor for this design is that it would be designed for a specific type of strut.  In this particular case I designed it for use with tubular struts of 1 inch nominal pipe size. Even with a universal connector, I think you will have to have some compromise somewhere. 

If possible, this weekend I will 3d print some prototype parts to see how the design functions.

Robert

[Ashok Mathur]

Dear Eric

My understanding is that in the design 

of the universal hub, which is the main topic,

 there is no need to worry about assymetric 

loading.

A minor point.

Regards

Ashok

Sent from my iPhone

On 01-Mar-2024, at 7:21 AM, Robert Clark <clark.rob...@gmail.com> wrote:

Eric,

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/0c132454-4b26-45f1-9df1-c50aebd9992bn%40googlegroups.com.

[Ashok Mathur]

Dear Eric

My design of a universal hub is a strong 

smooth central ring around which five or six , 

mostly six U bolts exist.

The U bolts spear a strut directly, or through a 

projection from the strut that allows the straight

 part of the bolt pass comfortably.

Initially the structure will look like something that

 the cat dragged out of an trash can, but once

 enough tension circuits are forged, the structure

 will acquire the necessary rigidity.

I can share a drawing if that is desired.

Regards

Ashok

Sent from my iPhone

[Eric Marceau]

Thank you, Ashok,

I believe that I can visualize you description, but some may not have as much facility.

Regarding that design, it seems that there would be "surface" protrusion which would prevent the "smooth" laying of panels over the triangular faces.

Was that your intent?

Eric

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/D1C542E2-7F5E-421B-860E-4EA459684951%40gmail.com.

[Ashok Mathur]

No.

Regards

Ashok

Sent from my iPhone

On 01-Mar-2024, at 8:40 AM, Eric Marceau <eajma...@gmail.com> wrote:



To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/b46fae18-acd0-450a-b5f1-983f83b59efc%40gmail.com.

[Dx G]

Sounds somewhat like what Paul Kranz was exploring, a ring based hub system.

Dx G

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[Ashok Mathur]

Dear DxG

You earlier wrote

“ This (presumably uneven loading of the dome)was investigated in detail back in the early dome days of the ones at the south pole, Montreal, Spokane and others that are well known now.   ”

At a later date you have also enclosed the report on the South Pole collapse .

For those who do not know it, that report can easily be downloaded from here

Unfortunately the very first line of the abstract shows that the dome itself was never the subject of investigation, it’s the snow compacted foundation of the dome that was the matter of investigation.

Regards

Ashok

Sent from my iPhone

On 01-Mar-2024, at 10:35 AM, Dx G <yipp...@gmail.com> wrote:



To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/CAF1iHD5CwC-TvU_sPbSAvxnOD5LWP16jCfzKgBuaFtRQcYKRRQ%40mail.gmail.com.

[cari]

Everyone!
We introduce a connector that allows anyone to create a dome house. It is a powerful tool that allows you to assemble the dome without looking at the complicated angles of the connector (HUB). This product is covered by Korean patent KR101310328B1.

https://global.gmarket.co.kr/item?goodsCode=2531102756

[cari]

2024년 3월 1일 금요일 오후 5시 49분 5초 UTC+9에 cari님이 작성:

[Dx G]

Very nice. Thank you for informing us.

Is this available in the USA, and if so, how would it be purchased?

I see the connectors can be rotated at different angles around the hub to provide different face angles.  Is it also possible to move the connectors up and down, in a bending direction, to provide different axial angles?

If not already available, it would be useful if you provided connectors that would accept round struts, such as pipe or tubing. These could possibly interchange with the rectangular connectors shown in the photo, or perhaps be an adapter that allows round struts to be used with your existing rectangular connectors.  I believe that would extend the range of the product and possibly increase sales.

Many thanks

Dx G

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[Dick Fischbeck]

I agree. And if the struts were telescopic and locking ...

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[Dx G]

Ashok,

   Well, that's not the way I read it.   If you read further, I think you will see the entire subject of the research was the tendency of a dome collapse.  The load originated from a snow "berm" piling up on one side, distorting the foundation, generating an asymmetric load (differential displacement).  The measurements, data and discussion specifically address the loads on the dome which could contribute to collapse, and that was the entire purpose for the study.  However, there are other studies that look at dome collapse from more direct asymmetric stresses, that do not include distortion of the foundation. 

"In the nonlinear analysis the strategy was to apply idealized differential displacements incrementally to the base ring in magnitudes sufficient to lead up to collapse of the dome. The structural analysis results are presented using computer graphics. Member stresses and structure deformations at various stages of loading are shown and analyzed."

"Results from the bending model of the nonlinear finite element analysis showed that the dome could sustain at least twice its existing differential settlement without significant structural consequences. "

Looks to me like another example of how resilient domes really are.  Perhaps even in something like an earthquake or a mudslide they might possibly tolerate structural distortions that could wreck an rectilinear structure unless it could resist the stresses as well.

Dx G 

To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/213DCF53-793F-4824-88F5-783EA4E4A0FD%40gmail.com.

[Ashok Mathur]

I defer to the author who wrote the abstract.

Regards

Ashok

Sent from my iPhone

On 01-Mar-2024, at 10:01 PM, Dx G <yipp...@gmail.com> wrote:



To view this discussion on the web visit https://groups.google.com/d/msgid/geodesichelp/CAF1iHD7VmsQZk2YPvgU-odAb_MjF8vHwGRgLfGkiRVurSRkQLQ%40mail.gmail.com.

[Dx G]

As per some comments Eric made earlier, I have added item 2a to my original list and reposted below. I consider this an oversight on my end, that should have been posted with the original list.  Readers should also review the proposed consolidated version proposed by Robert and the ensuing discussion.  

    I am grateful to those who have shared their work and thinking with the group on related creative effort. Other additions, deletions and corrections are welcome. 

The presumption is that a universal strut connector will make domes easier for people to make, assemble/erect and/or use.  One big issue has always been the compound angle, which is a problem for a lot of people, even those who build things. In particular, part of the endeavor is finding a design approach(s) that lends itself to using materials considered surplus, or even discard, which would otherwise end up in a land fill.

 
  General objectives are as follows for the hub:

1) Can accept a variable number of struts, often 5 or 6, but others as well.

2) A single design allows different face, axial and dihedral angles without requiring machining operations such as cutting, bending, drilling, etc.  That is, they are interchangeable without compromising strength and not risking structural failure.
  In addition, the part itself does not require precise angle and dimensional machining tolerances and is, to some extent, self adjusting.

2a)  Ideally, in all configurations, the connector successfully operates in compression, tension, torsional and other forces.

3) Can be used with different strut materials (wood, metals, pvc, even bamboo, etc.)
 
4) Can be used with different strut shapes (hollow round pipe or tubing, round solid rod, square or rectangular cross section, etc.)

5) Hub can accept plain cut struts, where the ends do not require machining (drilling, compound angle cuts, etc.) and other customized modifications.  Nor do the struts require specialized ends or caps to be attached in order to join them properly.  This objective can be a real asset for something like bamboo, where the brute force approach of using lag bolts or even machine bolts are not good choices.

  In particular, the intention is to join parts in ways that strengthen the structure, rather than weakening the connections among structural elements.
 
6) The hub design also lends itself to use with panelized domes that require various face, axial and dihedral angles for proper assembly.

7) Does not require specialized materials or parts.
Ok, this one is part of my continuing rant.
 When I look at dome parts in the patent literature, and even in the market place, too many require complicated schemes that have to be made especially for that intended use, and aren't good for anything else. We see this even more now with the use of 3D printers. Often, this approach requires different parts for different domes, or even different hubs, so hubs or strut ends are not interchangeable and have to be custom made. Although the inventors may believe that this complexity protects them from being copied, the down side of that approach is that many such inventions go nowhere and quite a few are abandoned.
  For purposes of expanding the adoption of domes, IMHO it makes more sense to use materials that are commonly available, manufactured in large volumes for something else (PVC pipe, as an example) that will likely be around for a while, whether or not they are used for domes. This also helps keep the price down and availability up, unlike some of the wacky designs I see in some of the patents that would cost a fortune to fabricate and have little chance of ever being made in volumes that would make them more affordable.
  Thus, the motivation for this item 7, here in my list.

Sound like a tall order?  Well, as Henry Ford famously said, whether you think you can, or think you can't, you are probably right. As I usually tell myself, well, if you think you're so smart, why don't you do it? So I'm workin' on it.  

I invite discussion from anybody making any advances in this direction, or otherwise interested in the same.

Dx G  

[cari]

Thank you for your interest in the connector. As you advise, we must now use square lumber, but the product can be made so that round members can also be used. The product in the photo is a connector used to build a small to medium-sized dome, and the connector product for building a very sturdy dome can be custom-made.
Although we cannot 100% accept the importance of angles in dome structures, we can accept 98% of them, including dihedral angles. It is also the result of 20 years of research to make it easy for anyone to build a dome house.
I hope this will be helpful to many people who want to create a dome house.

2024년 3월 2일 토요일 오전 12시 30분 17초 UTC+9에 Dx G님이 작성:

[cari]

Thanks friend.
You can purchase the connector at a shopping mall operated in South Korea, and purchase the quantity according to the attached data. Please note that international shipping costs may be added separately depending on the country.
Where to buy: https://global.gmarket.co.kr/item?goodsCode=2531102756

2024년 3월 2일 토요일 오전 12시 30분 17초 UTC+9에 Dx G님이 작성:

Very nice. Thank you for informing us.

[Dx G]

I've been engaged in an email conversation with Dick Fischbeck I wanted to share with the group. This was prompted by an idea I came up with related to the universal strut connector, an ongoing preoccupation of mine.  
  As recognized by the US Patent office, Dick is the inventor of the randome. If this is unfamiliar, I suggest these items to start, but there is more available:

USPTO Patent nr 7389612
https://www.youtube.com/watch?v=kY-5eXBp0FQ
https://archive.bridgesmathart.org/2004/bridges2004-347.pdf


The idea is really relatively simple.  

A randome has no struts, as it is made of a number of overlapping conical plates, a bit like fish scales.  So if one were to use only the top of the cone at the apex, one would have a "hub" of sorts to connect struts. Conceptually, this provides a strut connector that satisfies many of the requirements of the universal strut connector (appended at end.)  It isn't "perfect", but I'm looking at how to address a few possible downsides of the approach.

One thing I do like about using cones as hubs is the simplicity.  When I look at hubs, or other methods of joining struts at compound angles, my engineering snobbery gets the best of me. Hubs I see for sale, or in patents, tend to be complicated, incapable of accommodating more than one strut count, axial, face or dihedral angle and sadly rather expensive.  
   Hubs from cones (even adjustable ones) can be made with less cost, with less material waste, and could even utilize surplus or discard material that might otherwise wind up in a landfill.  They even provide some interesting options for emergency housing in disaster areas which typically have a wealth of useable materials, literally just lying around, that only looks like junk to most people, in the form of storm debris. In addition, providing a highly portable machine, or collection of tools, that allow one to make the cones from raw material (like sheet metal or others suitable) on site could be another asset, especially if the fabrication equipment could run without the need for electric, compressed air, etc.
    As is said, you have to see the invisible to do the impossible.

I may or may not be the inventor of this concept. My dome library is extensive, and for several decades I've been going to dome raisings, listening to talks and reading about space frames, shell structures and domes. However, oddly, I've never seen this discussed, proposed or otherwise described anywhere. Its always possible its there, and I've simply missed it, so if anyone is aware of any mention, or "prior art", any leads would be appreciated. Perhaps somebody has already more fully developed the concept and came up with useful related ideas.

  A related note on intellectual property.  
Several years ago, the USA joined the rest of the world in using "first to patent", rather than "first to invent" to establish inventorship.  Unfortunately, some people think this meant they can take ideas they get from others, file promptly before they do, and claim inventorship rights via first to patent. If they do succeed, all a patent really does is allow the patent holder to prevent others from using the invention without permission or payment, until the patent expires. For those of you who might want to explore this concept on their own, perhaps use this for prototyping or even as part of an actual business, keep this message in storage.  Even if someone files and is awarded a patent for this concept, public disclosure of an idea renders it unpatentable.  So unless a patent predates this posting, if someone tries to prevent you from using cone hubs, you can send them packing and even possibly invalidate their patent entirely by just providing a copy of this message.  

So, I'm giving this one away and you are encouraged to carry it further.  I still believe the availability of a universal strut connector could be an important element in the adoption and proliferation of domes. Cone hubs could be a useful rung in that ladder.

Dx G


-------------------------
 Universal strut connector
https://groups.google.com/g/geodesichelp/c/WVNShxVRr0c/m/_iGv9hZFBAAJ

From: Dx G <yipp...@gmail.com>
Date: Fri, Mar 1, 2024 at 4:28 PM
Subject: Re: Design of a better hub - domes and space frames - The universal strut connector
To: Geodesic Help Group <geodes...@googlegroups.com>

As per some comments Eric made earlier, I have added item 2a to my original list and reposted below. I consider this an oversight on my end, that should have been posted with the original list.  Readers should also review the proposed consolidated version proposed by Robert and the ensuing discussion.  
    I am grateful to those who have shared their work and thinking with the group on related creative effort. Other additions, deletions and corrections are welcome.

The presumption is that a universal strut connector will make domes easier for people to make, assemble/erect and/or use.  One big issue has always been the compound angle, which is a problem for a lot of people, even those who build things. In particular, part of the endeavor is finding a design approach(s) that lends itself to using materials considered surplus, or even discard, which would otherwise end up in a land fill.
 
  General objectives are as follows for the hub:

1) Can accept a variable number of struts, often 5 or 6, but others as well.

2) A single design allows different face, axial and dihedral angles without requiring machining operations such as cutting, bending, drilling, etc.  That is, they are interchangeable without compromising strength and not risking structural failure.
  In addition, the part itself does not require precise angle and dimensional machining tolerances and is, to some extent, self adjusting.

2a)  Ideally, in all configurations, the connector successfully operates in compression, tension, torsional and other forces.

3) Can be used with different strut materials (wood, metals, pvc, even bamboo, etc.)
 
4) Can be used with different strut shapes (hollow round pipe or tubing, round solid rod, square or rectangular cross section, etc.)

5) Hub can accept plain cut struts, where the ends do not require machining (drilling, compound angle cuts, etc.) and other customized modifications.  Nor do the struts require specialized ends or caps to be attached in order to join them properly.  This objective can be a real asset for something like bamboo, where the brute force approach of using lag bolts or even machine bolts are not good choices.
  In particular, the intention is to join parts in ways that strengthen the structure, rather than weakening the connections among structural elements.
 
6) The hub design also lends itself to use with panelized domes that require various face, axial and dihedral angles for proper assembly.

7) Does not require specialized materials or parts.
Ok, this one is part of my continuing rant.
 When I look at dome parts in the patent literature, and even in the market place, too many require complicated schemes that have to be made especially for that intended use, and aren't good for anything else. We see this even more now with the use of 3D printers. Often, this approach requires different parts for different domes, or even different hubs, so hubs or strut ends are not interchangeable and have to be custom made. Although the inventors may believe that this complexity protects them from being copied, the down side of that approach is that many such inventions go nowhere and quite a few are abandoned.
  For purposes of expanding the adoption of domes, IMHO it makes more sense to use materials that are commonly available, manufactured in large volumes for something else (PVC pipe, as an example) that will likely be around for a while, whether or not they are used for domes. This also helps keep the price down and availability up, unlike some of the wacky designs I see in some of the patents that would cost a fortune to fabricate and have little chance of ever being made in volumes that would make them more affordable.
  Thus, the motivation for this item 7, here in my list.

Sound like a tall order?  Well, as Henry Ford famously said, whether you think you can, or think you can't, you are probably right. As I usually tell myself, well, if you think you're so smart, why don't you do it? So I'm workin' on it.  

I invite discussion from anybody making any advances in this direction, or otherwise interested in the same.
Dx G  

From: Dx G <yipp...@gmail.com>
Date: Sat, Feb 17, 2024 at 9:41 AM
Subject: Re: Design of a better hub - domes and space frames
To: Geodesic Help Group <geodes...@googlegroups.com>

 Sorry, got chopped off here, so completed below:

Robert,
  Nice work.  There are certainly advantages to brevity, and you offer some wording which are improvements.  However, in some cases, there are some specifics I would prefer to retain for emphasis.

For example, the best hub would accept "plain cut" struts (my item 5)
Perhaps there is a better term, and in this case, this reference to the strut ends declares what the strut end *is* rather than what it *isn't* (i.e. (your item 4, lack of machining, etc.) .  The concept being that the strut end(s) can be used as it is found, such as from surplus or discard material, or, in other cases, as it would usually/conventionally be cut into pieces. I can't tell you how many job shops and machines I've seen,  set up to cut right angles and are literally incapable of being use to cut any other angles in any plane, much less a compound angle.   The idea is that even nasty ends that may have been twisted apart could be used without any modification if sufficiently straight and free of other disqualifying defects.

I will see what else I can learn about the Brujodesica System.  Initially, it appears to do what a lot of hubs I've seen do - they enjoy simplicity, but give up some strength and logistic issues. Without shims and an array of careful cuts, I can imagine some troublesome faults.  I will see if that is simply a result of and understanding gap on my part.

In any case, I am grateful for your review, comments and interest.  I believe the holy grail is more within reach than most people believe.  I intend to stay on the trail to the grail.   :-)
Dx G

On Saturday, February 17, 2024 at 9:09:37 AM UTC-6 Robert Clark wrote:
Dx G,

Thank you for taking the effort and time to detail the issues that should be addressed in a search for a hub design. I rewrote it in a little more concise form for my own better understanding.

"I've been working on a project to simplify dome construction and usage. One major challenge has been dealing with the complex angles involved, which can be daunting for many people, including builders. My goal is to develop a hub design that addresses several key objectives:

Flexibility: The hub should accommodate varying numbers of struts, typically 5 or 6, but it should work with other configurations as well.
Versatility: A single design should allow for different angles without needing special machining operations like cutting or bending. This ensures strength and structural integrity without precise machining tolerances.
Compatibility: The hub should work with different materials (wood, metal, PVC, bamboo, etc.) and shapes (round, square, rectangular) for the struts.
Ease of assembly: Struts should not require complex machining or specialized ends/caps for joining. This is especially important for materials like bamboo where traditional fasteners may not be suitable.

Strengthening connections: The design should reinforce the structure rather than weaken it at connection points.
Adaptability: The hub should also be suitable for panelized dome constructions that require various angles.
Accessibility: Avoid reliance on specialized materials or parts to keep costs down and increase availability.
Many existing dome designs in patents and the market are overly complex and require custom-made parts, limiting their practicality and adoption. By using readily available materials and standard manufacturing techniques, we can make domes more affordable and accessible.

This might seem like a daunting task, but as Henry Ford said, whether you believe you can or can't, you're probably right. I'm committed to working on this challenge and welcome input and collaboration from others interested in advancing dome construction."

The hub that can meet all these requirements is truly the sought-after holy grail of geodesic hub design. It would be the ultimate universal dome connector. However, I don't think there can ever be a "one-size-fits-all" hub design. This is simply because domes have so many different intended uses, sizes, and strength requirements. When designing a somewhat universal hub, we should consider these factors and then brainstorm for a solution for that narrowed-down set of requirements. I believe this will be more practical and achievable.

I'd like to share some pictures of a simple and unique hubless design by the group Ctrl+Z. They use recycled rough-sawn wood cut and assembled with simple tools. Many of you have probably already come across this on the internet. They call it the Brujodesica System. Here it is:

Brujodesica-Easa-2.jpgAlexandra-Kononchenko-9.jpgAlexandra-Kononchenko-8.jpg

On Wednesday, February 14, 2024 at 12:48:23 PM UTC-5 Dx G wrote:

I've had an ongoing project to make domes easier for people to make, assemble/erect and/or use.  One big issue has always been the compound angle, which is a problem for a lot of people, even those who build things. In particular, part of the endeavor is finding a design approach(s) that lends itself to using materials considered surplus, or even discard, which would otherwise end up in a land fill.

 
  General objectives are as follows for the hub:

1) Can accept a variable number of struts, often 5 or 6, but others as well.

2) A single design allows different face, axial and dihedral angles without requiring machining operations such as cutting, bending, drilling, etc.  That is, they are interchangeable without compromising strength and not risking structural failure.
  In addition, the part itself does not require precise angle and dimensional machining tolerances and is, to some extent, self adjusting.

3) Can be used with different strut materials (wood, metals, pvc, even bamboo, etc.)
 
4) Can be used with different strut shapes (hollow round pipe or tubing, round solid rod, square or rectangular cross section, etc.)

5) Hub can accept plain cut struts, where the ends do not require machining (drilling, compound angle cuts, etc.) and other customized modifications.  Nor do the struts require specialized ends or caps to be attached in order to join them properly.  This objective can be a real asset for something like bamboo, where the brute force approach of using lag bolts or even machine bolts are not good choices.
  In particular, the intention is to join parts in ways that strengthen the structure, rather than weakening the connections among structural elements.
 
6) The hub design also lends itself to use with panelized domes that require various face, axial and dihedral angles for proper assembly.

7) Does not require specialized materials or parts.
Ok, this one is part of my continuing rant.
 When I look at dome parts in the patent literature, and even in the market place, too many require complicated schemes that have to be made especially for that intended use, and aren't good for anything else. We see this even more now with the use of 3D printers. Often, this approach requires different parts for different domes, or even different hubs, so hubs or strut ends are not interchangeable and have to be custom made. Although the inventors may believe that this complexity protects them from being copied, the down side of that approach is that many such inventions go nowhere and quite a few are abandoned.
  For purposes of expanding the adoption of domes, IMHO it makes more sense to use materials that are commonly available, manufactured in large volumes for something else (PVC pipe, as an example) that will likely be around for a while, whether or not they are used for domes. This also helps keep the price down and availability up, unlike some of the wacky designs I see in some of the patents that would cost a fortune to fabricate and have little chance of ever being made in volumes that would make them more affordable.
  Thus, the motivation for this item 7, here in my list.

Sound like a tall order?  Well, as Henry Ford famously said, whether you think you can, or think you can't, you are probably right. As I usually tell myself, well, if you think you're so smart, why don't you do it? So I'm workin' on it.  

I invite discussion from anybody making any advances in this direction, or otherwise interested in the same.  

Dx G

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On Sat, Feb 17, 2024 at 9:44 AM Paul Kranz <pa...@revivetheflame.com> wrote:
Dx G: Maybe instead of a universal hub you could go with a universal hub maker. Inputs would be the class and frequency and the output would be the hubs required. A sort of 3-D hub printer. Paul sends...

From: Dx G <yipp...@gmail.com>
Date: Sat, Feb 17, 2024 at 10:42 AM
Subject: Re: Design of a better hub - domes and space frames
To: <geodes...@googlegroups.com>

Thanks guys.

Robert - yes, I can see the value of looking at the data. However, keep in mind that those numbers come from our *current* system of making hubs.  We would have to reflect on how the selection of what domes, spaceframes or other structures we build would change if some of our current constraints were lifted.

Paul,
 A good thought, thanks for sharing that.  Not my intention to be negative or critical, but a few follow up points meant to help clarify what I'm chasing.

(Note, I may be misleading readers somewhat by using the term "hub".
   A hub congers the thought of one piece of hardware (like some plate) that you'd use to plug struts into.  So perhaps I need to use a different term.  The real key is how to join struts, perhaps without the use of one physical hub object.  If you look at Hoberman Spheres, you can see one such example of how frame elements can be joined, although I recognize it doesn't meet the criteria I've laid out. )  NASA has also looked at this on and off for years as well.
   So, I'll start calling it a connector, instead of a hub.

1) The user would need such a device (the 3D printer type machine)  for this to work.  With the other approach, they would just need the connectors, which would, theoretically, attach/connect "any" struts.  Also, that device needs inputs (power, fabrication material, etc.), things some locations may not have, especially disaster areas trying to get housing up fast.  Those folks might make better use of a shipping container full of connectors (and they are all the same).

2) Recycle and carbon footprint issues
Sure, a device that can make this hub or that hub. That really works very well in a lot of settings. However, it also proliferates hub types. Once you make a 5 strut hub, you can't use it as a 6 strut hub.  The other approach does not have that constraint, since that connector works with "any" strut or strut assembly.
    One of the things this offers is reduced waste. It would be possible to reuse the connectors from one dome and use them for another. Whether a dome came down from storm damage, intentional demolition or other circumstances, it would be theoretically possible to reuse the connectors, if still intact, even in an entirely different dome. For example, taking them from a dome based on an icosahedron and using them to erect an octahedral.  That is, once we have invested materials and energy fabricating these connectors, I can see where they may have a longer life, and be a better long term investment that making all these different hubs.  
    Further, one would have to look at the materials and energy it takes to make the device, the input materials, and then support its use in the production of hubs (gotta plug it in some place).  This would have to be compared to the same inputs, and production equipment, required to make the connectors themselves.   In the case of the device, you do have a choice of shipping the machine and input materials to the construction location (decentralized logistics), or just sending the required hubs.  Less likely you would have the decentralized option with the connectors.   In addition, if the connectors really were all the same, there is a certain economy of scale in making large volumes of a single item, so hopefully automation would reduce the cost.   The jury is still out on which approach has more such advantages.

Partly I post this to help inspire others to consider the possibilities and think about the issues.  I think it is likely that the brain trust will come up with ideas I do not or would not have.  So even if success is beyond my own grasp, then someone else will have longer reach.  The real key is that the existence of such a connector/system could be a true inflexion point in the adoption of domes, and perhaps make better use of surplus and discard materials that are piling up in our landfills.

Dx G

[Robert Clark]

Is the randome commercially available? I've seen this picture of one.

[Dx G]

Interesting distinction among the structures from overlapping plates.  They may look the same, but one subtle difference is whether they are made of flat materials pulled into a cone shape, in contrast to others made of single plates molded into a curve (like a radar dish).  I wondered about that too, but Dick once pointed this out for me, since I wasn't clear on that distinction originally. 

Dx G

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[Levente Likhanecz]

https://www.novadome.com/product/mini-series/

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[Dx G]

Hi Dick,
 As part of the discourse we've been having, I thought I'd post this one to the group since it may be of some interest or use to others.
 
 You asked a question about my use of the phrase "junction of struts" with respect to my own concept of the Universal Strut Connector (USConn).

 The way I see it, the USConn concept is the broad class of constructs that are a "junction of struts".  
 
 That could include a "hub", which would be a part or an element separate from the struts themselves.  You could see these as a subclass of sorts within the USConn concept. The simpler hubs are just a short piece of pipe or tubing which acts as the center of struts joining radially. Others, like the cone hubs I described in an earlier posting (3/15/25), provides more of the features called for in the list of the "perfect" USConn.  I remain perplexed about why I have never seen this one even mentioned (let alone sold anywhere) despite a long history of reading and exploring dome/space frame information.  I'm inclined to think it has simply been overlooked rather than abandoned due to insufficiencies.  Your own videos and publications do a nice job of illustrating how to make them, and I'm working on some of the math to help set the cone fabrication/material specs up to work for various critical dome angles.

 On the opposite end of the spectrum would be what we see when triangular frames (for panels) are joined, a "junction of struts", in this case, with no "hub" per se. However, this approach is typically quite fixed and would not be a good candidate for a USConn.

 So in between those two extremes lies different approaches for a USConn. Some will satisfy more of the desired USConn features than others. I have a few I like under development and will know more after I load-to-failure to see what they can stand.

Hope that helps.
 Dx G

[Dx G]

After some additional thought and several side discussions, I have added two items to the Universal Strut Connector (USConn) list posted in March 2024.  lThey include:

--------------
8) The connector can be installed during dome construction with minimal labor and time, preferably without a need for tools or fasteners. Consider how this is like using a belt on pants, as everything you need to properly install it is already present with the device.

9) The connector installation is reversible. It can be installed, removed and reused repeatedly without degradation.
-----------------

Desirable attributes for the Universal Strut Connector (USConn)
 additions of 4/27/24 (items 8 and 9) to list posted March 2024

1) Can accept a variable number of struts, often 5 or 6, but others as well.

2) A single design allows different face, axial and dihedral angles without requiring machining operations such as cutting, bending, drilling, etc.  That is, they are interchangeable without compromising strength and not risking structural failure.
  In addition, the part itself does not require precise angle and dimensional machining tolerances and is, to some extent, self adjusting.

2a)  Ideally, in all configurations, the connector successfully operates in compression, tension, torsional and other forces.

3) Can be used with different strut materials (wood, metals, pvc, even bamboo, etc.)
 
4) Can be used with different strut shapes (hollow round pipe or tubing, round solid rod, square or rectangular cross section, etc.)

5) Hub can accept plain cut struts, where the ends do not require machining (drilling, compound angle cuts, etc.) and other customized modifications.  Nor do the struts require specialized ends or caps to be attached in order to join them properly.  This objective can be a real asset for something like bamboo, where the brute force approach of using lag bolts or even machine bolts are not good choices.

  In particular, the intention is to join parts in ways that strengthen the structure, rather than weakening the connections among structural elements.
 
6) The hub design also lends itself to use with panelized domes that require various face, axial and dihedral angles for proper assembly.

7) Does not require specialized materials or parts.
Ok, this one is part of my continuing rant.
 When I look at dome parts in the patent literature, and even in the market place, too many require complicated schemes that have to be made especially for that intended use, and aren't good for anything else. We see this even more now with the use of 3D printers. Often, this approach requires different parts for different domes, or even different hubs, so hubs or strut ends are not interchangeable and have to be custom made. Although the inventors may believe that this complexity protects them from being copied, the down side of that approach is that many such inventions go nowhere and quite a few are abandoned.
  For purposes of expanding the adoption of domes, IMHO it makes more sense to use materials that are commonly available, manufactured in large volumes for something else (PVC pipe, as an example) that will likely be around for a while, whether or not they are used for domes. This also helps keep the price down and availability up, unlike some of the wacky designs I see in some of the patents that would cost a fortune to fabricate and have little chance of ever being made in volumes that would make them more affordable.
  Thus, the motivation for this item 7, here in my list.

8) The connector can be installed during dome construction with minimal labor and time, preferably without a need for tools or fasteners. Consider how this is like using a belt with pants, as everything you need to properly install it is already present with the device.

9) The connector installation is reversible. It can be installed, removed and reused repeatedly without degradation.

-Dx G

[Ashok Mathur]

Dear Dx

This is a good set of criterion and can evolve with time and insights.

Let us say that there is a subjective system that is used to rate a connector as to how close it comes to a rating of ten out ten as a universal connectors.

So far , as per your criteria there is none that rates 10/10.

Can you paste some connectors that rate say 8/10 so that others can think of improving them.

Thanks

Regards

Ashok

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[Dx G]

Ashok,

  That's a good thought, rating existing or proposed hubs.  However, my thought process would work differently.  I'd put the numbered criteria in column one as rows of a list, and have a candidate hub (or hub idea) in each column.  Then one could just check which criteria are satisfied.  This provides more side-by-side specific information than a single rating scale, although the last row(s) could be one or more rating scales, depending on how that rating is calculated, such as whether some criteria have higher weight than others.

 If one wanted to try such an exercise, here is a nice collection to start with.  Once one reviews the USConn list, in most cases it is very obvious whether or not a given hub, or strut connection strategy, does or does not satisfy that feature.   However, it is also useful to run some web searches on "dome hub" and other keyword combinations to view others that do not appear below, many of which are currently for sale.  Yet more can be found in the patent, research/engineering and commercial literature.   I've seen some that are quite interesting in "dome books" that I've never seen anywhere else, so it pays to review those too.

https://www.domerama.com/dome-basics/geodesic-dome-hub-connectors/ 

I would also point those interested to "cone hubs", which I wrote about earlier (see below). Seems to me that may have significant merit, and I have never seen this written about or alluded to anywhere.   Currently I am testing some prototypes as a possible USConn.  It does not satisfy all the criteria, but as the late great John Lewis said, don't hold up what's good for what's perfect.  The key question is will it help promote the proliferation of domes...

Dx G

-------------------------------------------

https://groups.google.com/g/geodesichelp/c/WVNShxVRr0c/m/rhZ83JVtAwAJ

From: Dx G <yipp...@gmail.com>
Date: Sat, Mar 15, 2025 at 1:31 PM
Subject: Re: Design of a better hub - domes and space frames
To: Geodesic Help Group <geodes...@googlegroups.com>

[Ashok Mathur]

Dear Dx G

An excel sheet with built in pivot tables may be a good way to keep the data , diagrams and rankings together.

Regards

Ashok

 

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[Robert Clark]

You've never defined your use for the domes or connectors that you want to design. In the design world, usually Form follows Function, not the other way around.  I am a mechanical designer with more than 20 years of experience. A Universal Hub Connector solution is actually not too difficult if you first specify the specific use you intend.

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[Dx G]

Robert, a fair point.   So let's try this on for size.

Look at all the hubs shown on the web site I pointed to. For that matter, look at any dome hub or strut connection strategy you have ever seen.   Some are currently for sale, easily found on the web, others are in the patent literature, yet more in the commercial or engineering literature, and many in dome books.

  Rather than trying to define the function of the connector, let's have the hub selected replaced by the USConn...for the same function.

https://www.domerama.com/dome-basics/geodesic-dome-hub-connectors/ 

Then, if this is "not too difficult" I would rejoice in seeing you, or anyone, propose one that satisfies the criteria on the list and checks all the boxes.   Although they may not define function, they do provide important design specs.  I for one would love to have such an item, would use it myself, and still believe its availability and affordability could be a game changer in the acceptance and proliferation of domes.   

However, as a designer, you can probably appreciate what HL Menken said in the 1920's.

For every complicated problem, there is a simple solution that won't work (...or perhaps, not too difficult?)    :-)

Dx G