Inexpensive Connector

[RC]

Here's an idea for those who want a cheap hub connector.  You will not be building a house with this, but it would be well suited for structures of about 20 feet in diameter.

The building industries is one of the best places to search if you are looking for inexpensive components mass produced in large quantities.  Off-the-shelf will usually provided the best cost solution for your project.

In this case, Simpson Strong-Tie manufactures the LSTA metal strap which is designed to resist tension loads in wood-to-wood applications. This light strap tie utilizes a staggered nail pattern to help minimize wood splitting. The LSTA is designed for use on the edge of 2x members.  They have many  length variations of the LSTA, but the LSTA15 and the LSTA18 have very convenient hole size and locations suited for creating a hub connector.  Screw holes are for #9 or #8 wood screws.  The straps are 20 gauge steel (.0375" thick) and galvanized.  At the time of this writing, they sell online for about $1.25.  Two connectors can be cut from each strap using metal shears.  For a 6-spoke hub, that equates to $3.75 per hub.  The central hole is 1/2" diameter, but because of the 6 overlapping connectors, I would use a 3/8" bolt to join them.

Please post if you know of any other similar products that can be utilized in this way to create connector hubs for domes.

[Dx G]

Nice work RC.   Here are a few additional related items:

1) It is possible to use 2 plates on each strut. By having one on the top and bottom, it is possible to "set" the axial angle.  Although a longer bolt is necessary (unless 2 short ones are used for each of top and bottom hub), having a short spacer, like a short piece of pipe in between or stack of washers can add stability if needed.

  Also, putting a ring (slice of pipe or round block) in the center helps increase the compression strength of the hub, especially if the strut ends are cut at the axial angle. However, the simplicity of what you show has its advantages unless more strength/stability is needed.

2) The arrangement you nicely illustrated for lumber can also work for tubing or other shapes by clamping, metal screws or other means of attachment.  One could also bend the strap axially to a matching curvature, but it would have to be worth the work. This could also be done with a roll former, although it pays to keep the bolt hole flat.  Lots of people have used hose clamps to attach perforated plumbers strap to various pipe/tubing struts for a quick light weight dome frame.

3) Several of those metal strap companies also sell a "gazebo" connector which is pretty handy.   Simpson GT6Z for example. They come in 8's, 10's and several others, other companies offer a 5 (for pent).  They have some limitations but also offer some convenience.

There is also the star plate that has been around for decades.  The face angle is fixed, but different axial angles can be accommodated with a wedge.

https://www.strombergschickens.com/category/Starplate-Dome-Kit

However, an advantage to your approach is that it allows for any face or axial angle.  Simple is best as long as simple provides adequate performance.   As they say in engineering, perfection is when nothing more can be taken away.

- DxG

[RC]

Once the wood dome is fully assembled with the connector plates towards the interior, extra stiffening plates could be added to the exterior of each vertices.  The connector plates would have to be tightly bolted together ahead of time in the proper angular configuration before screwing the star-shaped hub assembly to the exterior of the wood struts - otherwise there would be no room to access the nut to tighten it.  But, I do think it is doable.

The "gazebo" connectors, and for that matter, other metal star connectors are all very expensive.  Companies charge $20 or more per hub.  This is much more economical.  A 5-star hub is $2.50 for metal connectors and the 6-star is $3.75.  Also, there is the small added cost for screws and a nut and bold and washers.  Estimated cost for hub connectors when building a 3V dome is less than $300.

The idea was simplicity.  Only tools required is a saw for the wood, hand shears for the metal strips, and a wrench and screw driver to assemble.  I have already purchased materials with the intent of building a 16 foot diameter 5/8 greenhouse dome for my wife.  That will be done later this fall after I have finished interior house remodeling.

[lemondealc]

I dig the idea RC. Please keep us posted. Maybe you should try to build a smaller dome on a raining day just to prove the concept works. If you do take so e pictures and share them with us! 

I'd think you could 3d print this kind of part too w/ a kind of hinge. I'd like to comment further but I'm on my way to work. 

I continue to build with my hubs which are about $1 per hub after shipping.

Here is a video I made that describes them.

https://youtu.be/NkZOVbdJrWs

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