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Geodesic Dome Assembly

Intro

Strut Creation

Note: if you’re going to do this yourself, consider buying or borrowing real tools instead of the ones we describe below. After helping with another dome-style building project, it’s *much* nicer to have a drill press plus jig, an arbor press to flatten, and last but not least a Makita worm drive circular saw with a metal cut-off abrasive disk to cut the pipes. You can see pictures of all of these in action on Howard’s Nose-building Party page. I’m making lots of sparks with the Makita about halfway down. See also Howard’s Home Dome page for detailed power tools advice.

Bill of Materials

metal 3/4 electrical conduit
You can buy this at a big hardware store like Home Depot for $2.26 per 10 foot pipe. You need 65 pipes, for a total of

manual pipe cutter (or Sawzall)
About $25 if you don’t have one already. Or you could probably instead use a Sawzall if you’re cool enough to have one.

electric drill with a cord
Around $30. You can’t use a cordless drill for this, it’s not powerful enough.

titanium drill bits
They’re expensive ($7.50 each), but last longer than standard bits. We went through at least four bits.

sledgehammer
We used an 8 pound sledge with a 32 inch handle.

anvil
We used a combination vise/anvil, around $35.

  • work gloves
    Avoiding tearing up your hands. I’ve worn holes through a few pairs in the last few years, between dome-building and working the post-BM cleanup crew. It’s much easier to replace gloves than hands.
  • Cutting the Struts

    We cut two sizes of struts: the long ones were 76.3 inches, and the short ones were 67.6 inches. (See the Desert Dome Calculator page for how to get these numbers given that we want a 2-frequency 20-foot diameter dome.)

    A pipe cutter looks like this:

    You just twist the knob until the blade eats all the way through the conduit. There’s enough mechanical advantage that it’s not too much work to do one pipe.

    Assembly Notes

    If you work from the top down instead of the bottom up, it’s possible to assemble the 20′ dome with only a single person. You won’t even need a ladder until the final bolt-tightening pass. You’ll start with the pieces that will end up on top, and use the struts to “walk” the dome up at a few key stages. More people will let you do many tasks in parallel, so the assembly will go faster.

    Don’t tighten any of the vertex bolts until the very last pass – you definitely want things non-rigid for ease of assembly and so that gravity will help you make the entire structure level at the end. Just do the bare minimum to keep things held together, especially since you’ll need to disassemble some vertices in later construction stages.

    In these pictures, the struts are marked with electrical tape near the ends: black is long and blue is short. Note that on the schematic diagrams, long is cyan (light blue) and short is yellow. Clearly we didn’t pre-plan this perfectly, but redoing it is more work that it’s worth.

  • Each vertex requires one bolt, two washers, and a nut. There are 26 vertices. However, you definitely want a lot of spares – each time we build the dome we’ve stripped half the bolts.
    • bolts: 5/16 x 2-1/2 hex tap bolts, coarse thread
      The hex head of these bolts is 1/2 inch. I bought a box of 100 at Orchard Supply Hardware for around $10. You want the kind of bolt that has threading all the way up to the head.
    • nuts (5/16 inch)
      Likewise, these nuts fit into a 1/2 inch socket.
    • washers (5/16 inch)

  • All the struts should be between the two washers:
  • Assembly Sequence

    Start with the struts, cable-tied in bundles of 5 for easy transport: 30 short ones and 35 long ones.

    Lay down five shorts in a star shape. (Three of these struts are specially marked since they have holes drilled into them where the plastic hat mini-struts will be bolted on later.)

    Bolt the struts together at the central vertex. They’ll end up elevated a few inches off the ground at the center.

    Lay down five long struts, one along each side of the pentagon formed by the short ones.

    Loosely bolt the vertices, so that one diagonally vertical short is between two horizontal longs. The center point will now be further up off the ground. There’s absolutely no point in tightening these vertices past the bare minimum to hold the nut on the bolt, you’ll be disassembling them soon.

    At each of the five vertices, lay down a short, then two longs.

    For each vertex, unbolt it and add the three new struts (long, short, long). You will probably have to struggle to get all six struts on, since the flattened parts of the struts inevitably don’t quite fit together right at this stage. Do as much as you can to encourage them (lots of shaking and shoving). For pernicious ones, you can give up on gentleness: just screw the bolts through the strut holes. Although this will strip the bolt, it will by God make everything fit.

    You’ll “walk” the dome up higher. The three struts that you just added are the legs that you’ll use to walk it up. Yank up on a vertex, so that the struts are less criss-crossed. You might have to make sure the ends dig into the ground so that it doesn’t slip. As you circle the dome doing this for every vertex, it will gradually stand taller and taller. After three or four full circuits, it will be at the height you want, where the short struts are vaguely close to vertical.

    At each short strut, lay a horizontal pair of short struts, one on each side.

    There are two kinds of vertices to bolt at this stage. One kind has three struts: a short vertical between two short horizontals. The other kind has four struts: two slanted vertical longs and two horizontal shorts.

    At the three-strut vertices, lay down a short strut on both sides, then lay down a long strut on both sides, for a total of four struts.

    At the three-strut vertices, bolt the shorts to the vertex. Let the new struts end up on the outside of the structure. At the four-strut vertices, bolt the longs to the vertex. Let the new longs stay on the inside of the structure. (The short ends in the picture are attached to the neighboring 3-strut vertices.)

    You’ll now “walk” the dome up again, using the new struts as the legs. This time will be more work, since the structure is heavier. You’ll probably want to yank up on the vertex with one hand while positioning the struts at a sharper angle with respect to the ground with the other hand. You may also get better results by skipping to every other vertex so that yanking up doesn’t undo the work you just on the nearest neighbor . Although it may seem like you’re taking one step back for every two steps forward, after several circuits you’ll reach the point where the struts meet in pairs to form triangles.

    Lay a long strut between every pair of almost-vertical struts: that is, at the base of the triangles.

    Bolt the vertex so that each triangle has a long at the base.

    Go around to all the eye-level vertices and shake the structure from each one, to level everything out.

    Tighten the vertices, starting from the top and working your way down. Since the very top is now 10 feet tall, you’ll probably want a ladder for this part. The best tools to use are a fixed wrench for the outer bolt top, and a deep-well ratchet wrench for the inner nut.

  • Wrap the top five vertices to keep the sharp struts from abrading the tarps. This year, instead of towel scraps after the fact, we’re trying preventative wrapping before putting on the tarp with chamois tape (the kind you wind on the handles of tennis rackets). A roll is $2.50 for three strips, and two strips per vertex seems good.
  • Design Choices

    Some people use PVC or ABS plastic pipe, which is not nearly as strong as the metal 3/4-inch electrical conduit that we chose. I’ve seen many structures built out of PVC that didn’t make it through the storms. Remember, there can be gale-force winds on the playa – that’s 70+ miles per hour. The mental image to keep in mind: how well would your structure fare if you strapped it to the top of a van and drove it around a highway for a few hours?

    In our early experiments we tried using 1/2-inch conduit, but found that the struts were much too bendable. Our struts can’t support the weight of a human hanging from the middle, but the vertices can. (And we do in fact use some of the lower vertices as hammock tie points.) If we had wanted a climbing dome instead of a living dome, we would have had to use real steel pipe, which is stronger, heavier, and more difficult to cut than electrical conduit.

    Flattening the Ends

    We tried flattening the ends of the conduit with a heavy-duty vise, but it took much more time: several minutes instead of 30 seconds. Also, the vise mechanism clearly would not have stood up to doing all the pipes. In this case, the mechanical advantage of the long sledgehammer handle outweighed that of the vise screws.

    We bent straight 3-foot pieces of rebar into giant U-shaped staples. In 1999 we went overboard, and used two staples per strut. Getting them out took forever.

    In 2000 we started with only four staples total. This was underkill, and we were afraid the dome would fly away during the first windstorm. We ended up pounding in four more staples with a small hammer during the storm, since our sledgehammer was broken by then. (Before Burning Man, I had no idea that it was even *possible* to use up a sledgehammer!) This was not a win either. I think one staple per vertex is probably a good compromise.

    I’m also not convinced that the full U shape is the way to go, since hammering on the bend of the U often just flattens the bend instead of driving the shafts into the ground. Other people swear by candy canes, I’m pondering whether to try that next year. Tamara Munzner Last modified: Mon Jul 29 17:12:17 PDT 2002

    Geodesic Dome Assembly Intro Strut Creation Note: if you’re going to do this yourself, consider buying or borrowing real tools instead of the ones we describe below. After helping with

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