My first geodesic dome

topic posted Fri, March 18, 2005 - 8:07 AM by  desTroy
Hey all,

I’m building my first geodesic dome. Although, I’ve worked on PVC structures in the past, this will be my first metal dome. It’s a 30 foot diameter 4 frequency dome. I just had 1250 feet of ¾” EMT dropped in my back yard and could use some advice.

First, cutting it up. I’m armed with a hacksaw and / or tube cutter. However, I have 250 cuts to make and would really prefer using a power tool. I haven’t worked with metal much and I’m not all that familiar with the different types of saws that could be used for this application. I’d prefer not to spend over $100 on a small table top saw of some sort. Any recommendations on which type of saw may work best?

Flattening the ends. I cannot afford a hydraulic press. So, I’m flattening the ends in a vise. It’s a lot of work, but given the price of a hydraulic press, I’ll gladly do it. My main concern is that the vice will flatten in a straight line, creating weak points. Is there any way to get that rounded line other than using a die and a hydraulic press? Is it possible to use a die in conjunction with a vise?

One last question. Although, I’m sure I’ll found out once it’s up, how much weight do you think could be suspended from the center point without causing the structure to warp or collapse? 30 ft diameter. 4V design. ¾ inch EMT.

Thanks in advance. I’m sure I’ll run into more questions as I progress.

posted by:
  • Re: My first geodesic dome

    Fri, March 18, 2005 - 10:57 AM

    Making those cuts and spending under $100 I’d buy a 4 1/2” angle grinder. Don’t spend less than $50 for the grinder; you get what you pay for in this case. With the grinder and 1/16” cut off disc you should be able to make all your cuts just fine. You’ll go through a few discs and since you can get them a lot cheaper in bulk on eBay I’d buy them there.

    As for the vise I think it will work fine, what I would try in your situation is making a die plate. Find a piece of plate metal around 5”x6” and 1/2” thick. Drill a 1” hold through the middle of the plate and then cut it in half. Now you should have two 5”x3” plates with half circles across the top edge. Mount them to your vise with a silicon based glue or even a hot glue (as long as it is flexible). Press your pipe.

    With so many presses you might want to mount your vise on its side then support your work on a table. You’ll also want to use a small square to make sure both ends get flattened on the same plane; this will be a lot easier if your work is horizontal.

    I’ve never tried a die plate on a vise but I think it will work. Good luck let me know how it goes.

    • Re: My first geodesic dome

      Mon, April 11, 2005 - 7:49 AM
      Hey LM / all,

      I’m making good progress much thanks to your advice. Thought you might like to see. For lack of anywhere else to put them, I’ve added related pics to my profile. The 14” cutoff saw I mentioned can be seen in my setup pics. $40 @ Harbor Freight…can’t beat it. I also splurged (about $50) and got a monster vice that swivels with pipe jaws on the other side. I found these pipe jaws to be invaluable as an extra set of hands to hold your pipe while making the cuts. I tried to employ my wife as the pipe holder, but she ran when the sparks started to fly. I did use the “make your own die” idea with a slight modification. Instead of attaching the dies to the vice via adhesive, I drilled holes to match my vice jaws and replaced the original jaws with the new die plates. You can see a shot of a test crimp. I’m now just setting up to do my crimps, getting everything level and all. I’ll update my progress as I reach milestones.

      • Re: My first geodesic dome

        Mon, April 11, 2005 - 1:15 PM
        Very Nice. I get to live vicariously through you until I can start working on my new dome. You’re going to get a workout with the vise; you’ve got a lot of ends to crimp.

        ; )

        • Re: My first geodesic dome

          Tue, April 19, 2005 - 12:14 PM
          You were so right about the vise workout. To get a nice flat crimp I had to put a cheater bar on the vise and beat it with a sledge hammer. Even then after removing it from the vice I had to pound it on an anvil to get it truly flat. After only one hour my arms were mush, I had only 10 ends crimped and the vise was being reduced to a pile of metallic dust. The vise die plates held up well. However, it was apparent that the vise was not going to survive if I kept it up. So, off to Harbor Freight Tools I went and scored a 12 ton press (including its own set of die plates) for $99.99. Once I got that home I was able to do 50 ends in the same hour it took me to do 10 ends with the vise. The quality of the crimp was tons better. And no additional pounding was needed with the press.

          Most dome building information I referenced did indeed suggest using a press. I should have taken that advice, but I tend to need to prove (or disprove) things to myself. I’m sure for lighter material the vise method would work much better than it did in my experience. In the future, I’m suggesting anyone working with EMT or heavier steel forego the vice idea and invest in a hydraulic press. It’s so worth it.

          • Re: My first geodesic dome

            Tue, April 19, 2005 - 12:25 PM

            I’m glad you have got the press; I’ve been thinking of getting one for the shop myself.

            Because of my dome design the conduit pieces are only going to be 9” long (Real easy to handle). To speed up the process of pressing them I’m going to make a small press with my 20ton bottle jack. The die plate will allow 4 pieces to be crimped at once. Those ends will sleeve into 1” PVC pipe. Should be interesting.

          • Re: My first geodesic dome

            Wed, June 1, 2005 - 7:52 AM
            Hey Dome Builders,

            Sorry for not continuing to document my progress. Time started running short. I finished the dome just days before the deadline. We didn't even have time for a trial set up. Fortunately, it went up beautifully.

            A few details I've left out may be of interest to some. The dome was built for our mid-atlantic regional burn. I designed it for rope bondage suspension. At select restraint points, I used weight rated lifting eye nuts to which I attached 1-ton hoists. Indeed, the structure held the weight with no problem. I've attached 2 pics to my profile, 1 shows the bare dome, the other is an interioir shot after covering.

  • Re: My first geodesic dome

    Wed, April 20, 2005 - 5:50 PM
    Try freecycle! It's a yahoo group. You post what you want in your area and hopefully you get a response. You'll be surprised, I got a woodburning stove. As for flattening the ends, an arbor press would work well and they run from $25- $60 new or used check ebay. Check out
    • Re: My first geodesic dome

      Fri, April 22, 2005 - 1:02 PM
      Yes, has been my main reference. It's fun to just play around with their dome calculator.
      • Re: My first geodesic dome

        Wed, June 1, 2005 - 8:56 AM
        Hey all I just wanted to say that I got a chance to check out desTroy's dome at PDF just few days ago! Very nice and very large and I assume sturdy as well.

        The dome was fully constructed with I think five pulleys hanging from near the crown of the dome.

        I did find it rather funny that the carpet that you used to line the dome was from a church! Nice touch ;^)

        I didnt have time to come out and check out any of the shows at the dome. I was helping with the stage crew, we had alot to do and plus trying to enjoy the burn as well. We did put up a PVC dome in front of the stage this time. We where not supporting anything other than a couple of speakers, plus we can get that dome up in less than 30 mins w/a crew of experienced ppl.

        Anyways please put up photos of your grinder, and your hydraulic press and your dome to the photo album. I'm always looking for new stuff to put in the album rotation. The photo album is open to all dome related photos!
        • Re: My first geodesic dome

          Fri, June 3, 2005 - 6:18 AM
          Thanks for the first hand account, Doctor. Indeed it is large. Although, I knew how large it would be, I didn’t REALLY comprehend just how large it would be / look after assembly. When we finally got the bottom tier on and the dome was at its full height, we all went to the center, looked up and said “DAMN!!! That’s big.”. Then we stepped back from the dome to get a view of it from afar and still said “DAMN!!! That’s big.”. Although the 15’ ceiling is a bit excessive, the 30’ diameter allows for suspension in the center and various apparatus skirting the edges.

          I attached a 1-ton hoist to each of the 5 points radiating from the center. I first tested it with my own body weight dispersed between 2 of the points. I then climbed a rope hanging from a single point and did a little bouncing to see if the structure would flex or bend. If it was going to collapse, I wanted it to do so while I was testing it instead of it happening during actual suspension. It didn’t even wiggle.

          Our tallest ladder was 10’. So, we assembled it from the top down attaching the hoists as we went. Once it was up, we noticed 2 of our hoists were slightly askew. Even standing on the top step of the ladder, we were unable to reach the hoists well enough to make adjustments. As we’re pondering our predicament, a camp mate and general contractor had a brain storm. He was rather fuckered up by a recent visit to the Sangria Pirates, but he made sense. He had an industrial grade suspension belt for construction work. His idea was to have us hoist him up using one of the hoists while he fixed the two misaligned ones. At first we all laughed that he was so messed up he actually wanted to attempt this. Slowly, we started to realize, this will work. And indeed it did. He had fun flying like Peter Pan and threw up afterwards.

          Indeed, the dome is floored with carpet pulled from a church and you should have checked that stuff out. I’ve never seen such industrial carpet. The carpet itself is quite hefty, but it’s backed with ¼” of tough rubber. I picked up the 12’ x 27’ carpet for only $25! Basically, the pastor of the church offered it to a member of the congregation. Once said member had possession of the carpet, he realized it was much more heavier stuff than he needed. He didn’t feel right telling the pastor to take it back. So, he offered it up on craigslist for $25 and I was on it. I had to cut it in 4 sections just to transport it.

          I covered it with a 50’ square silver tarp, pulled the excess tarp under and into the dome and cut a door and windows for ventilation. That worked this time, but I plan to sew an actual cover made round to fit perfect.


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