Conduit, or EMT seems to be the material of choice for domes at Burning Man. Conduit is easy to work with, relatively inexpensive, and plated so painting isn't necessary. This page will provide tips for making conduit framed domes.
STEP 1: Deciding on a frequency
The first thing you need to do is figure out what type of dome you want to build. If this is your first dome, the 2 or 3 frequency domes are recommended. These domes require a fewer number of struts, and therefore less confusion.
STEP 2: What Size?
Once you have decided what kind of dome you are going to build, you need to decide on a size. Sometimes it is better to work out how long your longest or shortest strut will be and work from there. You can use the Reverse Dome Calculator when this is the case.
STEP 3: Calculating Strut Lengths
This is where the Dome Calculator comes in. Go to the calculator and plug in the radius that you decided on for your dome. If it's been a long time since your last math class, radius is the distance from the center to the edge of a circle or sphere. In this case, the radius is the ceiling height for the even frequency domes. For the odd frequency domes, the ceiling will be higher than the radius that you put in (unless you are building the 3/8 dome, in that case the ceiling will be lower).
1v dome builders: Cut all your pipe the same length and skip to Step 5.
Step 4: Eliminating Waste
This part is tedious, but worth the effort because it will save you money and you won't have to feel bad about throwing away tons of wasted pipe. You will have to repeat steps 2, 3, and 4 to do this right. It may take a while, but I would think you were a bad person if you didn't at least try. Conduit is usually sold in 10' lengths, so your job is to figure out how to cut those pieces eliminating as much waste as possible. Make sure to add 1½" for each strut to allow for drilling. For all you 2v dome builders, it's easy because there are only two lengths involved. The magic numbers for a 2v dome cut from 10' conduit pieces are A = 5.3', and B = 4.7'. These numbers allow for holed drilled ¾" away from the ends. 2v people may now skip to step 5. The rest of you: Still with me? Play with the numbers until you can get the maximum number of struts using the minimum number of conduit pieces. You may try 2 A's and 1 C, or 1 A, 1 C, and 1 F. Don't forget that different numbers of struts are required. Don't get stuck with more or less than what you need. I never said this was the easy part...
Step 5: Cutting the struts
Cut the tubes according to the strut factors plus 1½". This allows for drilling the holes ¾" from the ends. Cut the struts using either a hacksaw or a pipe cutter. If you use a hacksaw, 16 or 18 tooth blades work best. When making many cuts, it's always best to use a jig so all the struts are exactly the same length.
STEP 6: Flattening the ends
OK, there are a few ways to do this part. You can either pound the ends flat with a hammer, which could be really time consuming, or nearly impossible if you are as small as I am. You can also use a vise, but make sure it's a fairly large one so it doesn't break after a few squishes. The way I like to do it is to use a press. The press in the picture is a 1 ton arbor press bought at Harbor Freight Tools. It was really cheap, but only lasted about 20 squishes. The 3 ton press worked a lot better, but it started to bend after about 150 squishes. If you can afford it, a hydraulic press seems like the way to go. If you flatten the ends with a curved die like the one shown below, the ends will be stronger and therefore less likely to bend under load. (click image to enlarge) Please notice the weld along the side of the conduit. If you flatten the end with the weld on the side, the conduit will be likely to split there. It can also split if the weld is in the center of the flat part. I personally haven't had this happen, but I spend good money on dome parts, and would rather not learn the hard way. Keep in mind that the flattened ends need to be in the same plane. If you take a few minutes to construct a simple jig for this, I promise you won't regret it.
Step 7: Drilling Holes
To drill the first hole in each strut, cut a V groove in a 2 X 4 six inches longer than the longest strut. Clamp it to a drill press with C clamps. Use a stop block so that all of the holes are the correct distance from the end of the pipe (¾" from center of hole to edge of pipe). Use a 3/8" drill bit (you may need to buy several). Titanium costs more, but lasts the longest. This gives about ½" from the edge of the hole to the edge of the pipe. To drill the second hole, you will need to measure the exact hole-to-hole (aka strut) length, along the 2 X 4 and drill a 3/8" hole there. Screw in a 7/16 carriage bolt that has its head cut off with a hacksaw. It will be tight since the hole is smaller than the bolt, but trust me on this one. You can use a vise-grip or a pipe wrench to screw it in. File the cut-off stump to a slight taper so the holes in the pipe will easily slip over it. Clamp the 2 X 4 back to the drill press so that when the first hole is placed over the cut-off bolt, the other end can be placed under the drill in the correct position. Pull the drill down so it just touches the pipe, and double check your measurements. If they are correct, continue drilling with confidence. If not, you know what to do. Continue this process with all lengths moving the pin as necessary. It would also be a good idea to mark the table and the jig when you get it set so you can tell if it is moving.
Step 8: Bending the Struts
Now the struts need to be bent to the correct angles. You can do this by clamping the end into a vise and bending the tube to a stop block. If any of the flattened ends are split, bend the pipe toward the split side so the split will be on the inside of the dome. The accuracy of the bend is not as important as drilling the holes, so don't hurt yourself on this one. I repeat, the accuracy is not that crucial, don't spend all day deciding if you need to bend an extra degree or not! When the dome goes up for the first time, the struts will bend to the exact angles on their own.
The bending angles are as follows:
1v dome: bend 32º on each end
2v dome: bend A's 18º, and B's 16º on each end
3v dome: bend A's 10º, B's and C's 12º on each end
4v dome: bend all struts 7º-9º on each end
5v dome: bend all struts 6º-7º on each end
6v dome: bend all struts 5º-6º on each end
Step 9: Painting
The ends of the struts all need to be painted, because otherwise they will rust. Since you are painting anyway, why not color-code! I'm a big fan of color-coding, and when you try to assemble the dome you'll find out why. To make it even easier on yourself while you're in the desert, make a model using the same colors as in your dome. When you get to Burning Man, you can set the model down, lay out all of the struts, and sit back and relax while other people put it together for you. Well, not really, but it will make it a lot easier to put the dome together if you have a model as a reference.
Step 10: Break Time!
Take a break, cause that was hard work. If your camp is anything like ours, you can't take a break because you just finished the prep work for the dome 3 hours before it's time to leave for the desert...
Step 11: Assembly
Ahhh, the moment you've all been waiting for. Bet you're a little nervous if it's your first time. Don't be. If you followed these instructions carefully, your dome should go up smoothly.
Domes can either be built from the top down or bottom up, depending on the size of the dome, and your tallest ladder. Building from the top down eliminates the need for a ladder, but you better have a lot of people helping. As the dome goes up, you will need one person at every vertex holding it up. If any of your poles get bent during this process, you better hope you listened to me before and made extras. Bottom to top assembly is much safer on the dome, but it means you have to bring ladders and/or scaffolding tall enough to reach the top of the dome. I noticed several domes last year without tops. Build the dome in layers whether you are going from top to bottom or vise versa. Don't get ahead of yourself. If you build in layers, the dome will pretty much support itself as it goes up. It might be a good idea to designate one person as the parts person. All this person has to do is lay out the next layer of struts on the ground for the assembly crew. This prevents over anxious builders from getting ahead of the rest of the crew. Don't tighten the bolts until all of the struts are in place. The struts will shift into their proper alignments as the dome is built, and they can't do that if the bolts are tight. Remember the dome doesn't get its strength until the last strut is in place and all the bolts are tightened.
Here are the assembly diagrams for domes 2-6.
If you are building your dome from the bottom up, here is some useful information:
You will need to lay out the appropriate number of struts in a circle to get started. The numbers are given below.
1v dome - 5 struts
2v dome - 10 struts
3v 3/8 dome - 15 struts
3v 5/8 dome - 15 struts
4v dome - 20 struts
5v 3/8 dome - 25 struts
5v 5/8 dome - 25 struts
6v dome - 30 struts
Step 12: Staking Down
Please don't forget this part. If you cover your dome before you stake it down, you will not be a happy camper when it catches wind and smashes into the cars parked a couple of feet away. Rebar bent into candycane shapes work really well for stakes. Make sure they are at least 2 feet long. Pound them in about every other vertex along the bottom.
Step 13: Covering your dome
The whole purpose of this IS for shade right? If not, you can stop here.
Parachutes make really nice dome coverings because all have to do is pull the parachute over the dome and tie it down. The only problem with parachutes is that they were made to catch wind... Need I say more? You've gotten this far, you can make a covering. Be creative on this one. You can use bed sheets, canvas, or anything else you can think of. Reinforce all points that will be connected to the dome or they will tear with the slightest gust of wind.
Woo Hoo! Now that your dome is finished, you can sit back and relax, or wander around knowing that you have a really cool shelter to return to. Be sure to come and see us at Camp Sunscreen for a relaxing sunscreen massage. If you know where you and your dome will be, please e-mail me with your address so I can come check out your masterpiece and also take pictures for the photo gallery.
See ya on the playa!
Here are some other dome building tips pages.
My friend and fellow Camp Sunscreen camper's dome tips page - there are lots of pictures and very good tips
Michael Gourlay's Dome Page - Michael is another fellow Burning Man attendee