Dome Connection Clip


Introduction: Dome Connection Clip

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Update 12/11/15 The pictures now show the new scissor stainless steel clip made with a CNC process that is stronger and more universal for strut frames than the spring clip. The pivot hole can be adjusted easily to fit any size pipe or square tubing PVC, aluminum or metal. We've used these to replace and extend broken conduit ends that were used in event domes due to many set ups and take downs. The struts are saved and the new self aligning connection is installed easily. There is no need to calculate geodesic strut angles anymore as once the hub is bolted solid in relation to all the connected struts they align themselves between the hub placement.

I'm getting ready for a production run on the clips, I'd like to get some of these out there in the DIY market to show folks how easy it is to build a dome or any strut type structure such as a greenhouse. This clip can also be fixed at a set position into pipe or tubing by adding one more hole and tab on the clip.

In building domes I felt the need for a better and simpler connection. I've looked at numerous geodesic hub connections for PVC & EMT and none of them had the angle self aligning adjustment needed for a geodesic application. Lighting wire or sprinkler lines can be run continually alongside the clip into each tube and the reusable clip will work in PVC as well as EMT tubing. For instance, in a greenhouse dome that required steel or aluminum tubing you would use the PVC in the bottom row for corrosion resistance buried under the soil and the metal tubing above that.

Another way to explain the flexible connection joint is that proper geodesic struts ONLY experience tensile and compressive loading. There is NO lateral pressure IF the strut is exactly the correct length between the rigid hub centers. Any mis-alignment of the strut due to improper length, variation from a straight line or bent hub connection ends will create lateral pressure and degrade the natural triangular strength in the geodesic design.

Patent 9151035 and others.

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    13 Discussions

    Thanks for the interest. The self aligning hub really doesn't change anything as far as assembly order but does make it easier to put the vertex in place ahead of the final struts in the assembly. As much time and energy is wasted trying to control strut end angles when building geodesic domes. The angle is determined only by the length of the strut to the vertex point in the hub. Much like a sphere has an "eggshell" effect, the structure is synergetic as the whole shell resists compression providing amazing synergetic strength with the struts in perfect alignment with the hub. Buck Fuller used the term "synergetic" quite a bit to his credit. Although, he almost never used the word "angle" when describing the geodesic design.

    looking forward to this finally being a reality. Seems like a foregone conclusion that the worst part of dome assembly is hub angles. Does a hub like this also mean that, within reason, a dome could be assembled in a variety of orders (top down, bottom up, side to side?

    Yes, that might work on a super small light weight dome. The hub center holds the struts in alignment so you only need the pin axis strong enough to keep the lateral forces in check. I have an update of the joint using stainless steel that I can now build in my own shop. We can still keep the cost down for the average dome builder. I will post that here when I get it finalized.

    I have a friend with several event domes and at the crushed end of the conduit they are cracking due to angle flex from the many setups he has done. The new joint is long enough to allow the conduit to be cut behind the crack and reused saving buying a whole new set of struts.

    Unfortunately our government patent office has my lawyer clarifying the design for the final patent grant. A quick clip like this requires CNC machinery to build which I will purchase but I need to be legally protected before I spend that kind of money. My idea is to offer a simple clip so the average do-it-yourselfer can build their own domes without spending a bunch of money.

    Thanks.. I bought an initial production run of 500 clips to fit 1" EMT and 1" Schedule 80 PVC. Once they build a specific DFX file (strut size) for the CNC wire bending machine it's just a simple process to switch files and build clips for any size round pipe strut. I'm stuck in the legal process right now but the patent application should be due for grant status very soon.

    I love the simplicity! Have you made a production run yet? Are you selling them?

    Thanks for the great comments Rick and Rimar. In answer to maintaining rigidity which is a good observation that I had for awhile, I found having an axis on the end of the strut connected to a solid bolted hub seemed to relax the polygonal or closed plane of the solid hub connected struts into perfect angles. I remember Buck Fuller said once that he could use a flexible chain in place of the horizontal struts and form a perfect dome. We built a 30' 4V dome with 2 inch EMT to test the design using the flexible joint and it seemed to hold shape and was more rigid than using the non flexible semi solid pressed tube strut ends. IMO, I believe we proved Bucky was right on that point.