www.dragishak.com dragisa krsmanovic

Geodesic Dome Construction

  1. Design
  2. Cutting
  3. Compressing pipe ends
  4. Drilling
  5. Assembling
  6. Cover
Home

Design

I decided to build 5/8 geodesic 3V dome. All calculations and design you can see at Desert Domes. I calculated that I can build 12ft diameter dome using 41 1/2" steel conduit pipes. One horizontal bar will be removed to make and entrance for the door. So, total number of segments was 164. Conduit can be bought at Home Depot or electrical supply shops. It was a few cents cheaper at my local electric supply shop. I used an Excell spreadsheet to do all the calculations. Standard size of conduit is 10 feet and I decided to cut four pieces from each 10 feet pipe. Ideal lengths turned to be 26.05, 30 and 30.64 inches including 1 inch to make space for holes. Feel fee to use the spreadsheet for your projects. Try playing with different values.
Back to top

Cutting

After carefully measuring all the lengths, I went to the first phase of my dome building.

For cutting, I used abrasive cutting wheel with bench grinder. It was easy and fast. Keep in mind that the abrasive wheels wear off. So, disk diameter gets smaller. At some point, disk gets so small that you can't cut whole diameter of the pipe and you need to change the cutting wheel. It took one and a half wheel to cut 164 pipes. I worked with 1/2-inch pipes, but this method might not be suitable for larger diameter pipes because of the size of grinding wheel. Later, I got a metal cutting band saw and electrical conduit is an easy job for it.
Back to top

Compressing pipe ends

I needed to compress about one inch at the each end of the pipes. I used a heavy vise and a piece of steel pipe to get more leverage.

This turned out to be the most difficult thing. Both physically and technically. It took me about a week to compress all 164 pieces.

After about 80 pipes, steel washers at the handle of the vise started to grind and it became very difficult to turn the handle. I disassembled the vise, polished the washers and added a little grease to be able to continue. I had to repeat this process once more. It would be much easier if I had a press of some kind. If this was 3/4 inch conduit or bigger, this would be very hard to pull of with just a vise. Also, if you do it this way, with pipe in vertical position, it's more difficult to align flat parts at the both ends of the pipe.

Pay attention at weld join (see picture). Make sure that it's positioned at the center of the flat part. Otherwise, it's possible that pipe wall might break.
Back to top

Drilling

Drilling turned up to be a very easy task. Main thing is to get all jigs right. I used a heavy drill press.

First, I drilled one end of each pipe at 1/2 inch from the end of the pipe. I used a simple jig with a nail in a small wooden board and drill press vise. Make sure that each piece is secured before you start to drill. This is a strong machine and it might spin whole workpiece if it gets stuck.

Second, I set up a jig for drilling second hole. Here I used a longer wooden board with a nail at opposite end. First hole in pipe goes on the nail. I used several C-clamps to secure the wooden board and pipe while drilling.
Back to top

Assembling

Finally ! I was about to build my dome. It's simple if you pay attention. Just follow the instructions from Desert Domes.

Of course, I made an error at the beginning. So, I had to pull apart the dome to fix it. At the end result was great.

If you were precise when drilling the holes, assembly should be easy. I used cheap 1/4" screws, which tend to bend if you press too hard. It's not a big deal because the structure is very sturdy and can take playa winds with ease.
Back to top

Cover

Covering my dome was the biggest unknown. My first idea was to use a parachute. Parachute has two disadvantages. It catches the wind (that's what it's made for) and it's not perfect shade. So, I decided to use plastic silver tarp.

I wanted to have a cover that would fit oval shape of the dome. For that, I needed to figure out how to join pieces of plastic tarp together. Three options are: to sow them, to glue them or to heat weld them. Since I didn't have a industrial sowing machine, I decided to try welding plastic tarps.

Cover was assembled from one round piece at the top and five sides. In addition, I made two round windows to allow more air inside the dome.
Professional plastic welding equipment is too expensive. So, I decided to improvise. Polyethylene melts at around 120C (250F). Most of cheap heat guns can produce up to 500C (1000F). To join two tarps you need overlap them about 2" and, while blowing hot air in between the sheet, just when the plastic starts to melt, press them together with a small silicon rubber roller. It needs some practice but after a few hours my girlfriend and me were able to make some relatively strong welds. Joins are not as strong as if you would sow them but that turned to be strong enough for desert winds.

In addition to outer shell, I also cut a round floor and windows. I mounted steel snap buttons around the door and the windows for closing them. That didn't turn too practical. Stainless steel, snap buttons were too strong for plastic tarp and would rip off when you try to open them.

Grommets turned to be much more useful. I mounted them around the edges of the cover and around the edge of round floor tarp.
Back to top