Geodesic Domes are awesome. This Instructable will show you how I built a 20' dome for about $250, with the majority of that cost being the greenhouse plastic ($167 with shipping.) That's right, the structure itself cost less than $100! I will also write about what is wrong with this design, how it came about, what I learned from it, and what you might want to do if you're building your own.
Buckminster Fuller wanted his dome houses to be cheap, quickly constructed, and portable. Yes, your house was supposed to be able to be picked up with a helicopter and dropped off somewhere else! The Marines experimented with it in the 60's. There are pictures of domes being flown around.
My purpose for building domes is the same as Bucky's: to save humanity from extinction. We are currently building houses the same way as we did thousands of years ago. Bucky said we would adopt his new technologies only when it was absolutely necessary. Well, the time has arrived. Here is why YOU should be living in a dome:
1) They use far less material than a square building
2) They are much stronger, domes have withstood hurricanes and tornadoes, even a nuclear blast
3) They use less energy, the oft quoted amount is 30% less, but it goes up as the dome gets bigger
I am submitting this as part of the "Win A Home Fabricator" contest. If I had had one when this started, it would have shaved days off of construction and lots of frustration. My next dome will be made out of bamboo, and hopefully use home fabricated vertices (the connectors between the wooden struts.) So if you like this Instructable, please rate it highly so I can make a better dome next time, and work toward that goal of saving humanity from itself.
Buckminster Fuller wanted his dome houses to be cheap, quickly constructed, and portable. Yes, your house was supposed to be able to be picked up with a helicopter and dropped off somewhere else! The Marines experimented with it in the 60's. There are pictures of domes being flown around.
My purpose for building domes is the same as Bucky's: to save humanity from extinction. We are currently building houses the same way as we did thousands of years ago. Bucky said we would adopt his new technologies only when it was absolutely necessary. Well, the time has arrived. Here is why YOU should be living in a dome:
1) They use far less material than a square building
2) They are much stronger, domes have withstood hurricanes and tornadoes, even a nuclear blast
3) They use less energy, the oft quoted amount is 30% less, but it goes up as the dome gets bigger
I am submitting this as part of the "Win A Home Fabricator" contest. If I had had one when this started, it would have shaved days off of construction and lots of frustration. My next dome will be made out of bamboo, and hopefully use home fabricated vertices (the connectors between the wooden struts.) So if you like this Instructable, please rate it highly so I can make a better dome next time, and work toward that goal of saving humanity from itself.
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Signing UpStep 1: What type of dome
There are many choices in dome construction. I chose to build a 3/8 3v dome to keep the complexity low. This is where the 'designed on a computer" part came into play.
First, I used a program called Dome Designer to play with raw material lengths. It is very useful in calculating the amount of scrap that will be produced, and letting the user experiment with different dome frequencies and sizes. Unfortunately, it has a tendency to stop working, and then needs to be reinstalled in order to start again. Part way through the project, it stopped accepting my license key, and the creator never returned my emails. I wasn't about to spend another $100 on a program that doesn't work, so it was back to the web. In the end, everything I needed was online. The scrap length didn't matter on a dome this size anyway, so it was no loss.
The design tutorial that comes with Dome Designer was actually one of the most useful things I got out of my $100. In it, they point out that most domes are overbuilt. People making a house are used to using 2x12" boards, and think that it should naturally be the same with domes.
This is not the case. The stress that is put on dome struts is actually tension, instead of compression. Picture a drinking straw, standing vertically. Now put a stack of books on the straw. It immediately bends over and drops the load, breaking if it were something like wood. But what if you were to suspend the books from the straw? It could hold them until the end of time. This principle applies to domes, all of the force exerted on the struts is pulling, not squishing.
That's why I built this dome out of 1" (which is actually 3/4" in the real world) sticks, weak and many cracked. I wanted to see if they could hold up. More on the results of that later.
These are the most useful online tools I used:
Desert Domes has a number of great resources, the Dome Calculator and Reverse Dome Calculator being my most used. It is helpful for figuring out the length and number of struts, and number of vertices needed for different frequencies of domes.
Then I used this diagram during assembly.
Dome frequency is basically the number of triangles that exist in the dome. The higher the frequency, the stronger the dome, and the more complicated and more materials you will need. The one pictured is a 3v (frequency 3) 3/8 dome. The 3/8 means it is 3/8 of a sphere, so you can imagine just cutting the top 3/8 off a baseball, and that's what it will look like.
First, I used a program called Dome Designer to play with raw material lengths. It is very useful in calculating the amount of scrap that will be produced, and letting the user experiment with different dome frequencies and sizes. Unfortunately, it has a tendency to stop working, and then needs to be reinstalled in order to start again. Part way through the project, it stopped accepting my license key, and the creator never returned my emails. I wasn't about to spend another $100 on a program that doesn't work, so it was back to the web. In the end, everything I needed was online. The scrap length didn't matter on a dome this size anyway, so it was no loss.
The design tutorial that comes with Dome Designer was actually one of the most useful things I got out of my $100. In it, they point out that most domes are overbuilt. People making a house are used to using 2x12" boards, and think that it should naturally be the same with domes.
This is not the case. The stress that is put on dome struts is actually tension, instead of compression. Picture a drinking straw, standing vertically. Now put a stack of books on the straw. It immediately bends over and drops the load, breaking if it were something like wood. But what if you were to suspend the books from the straw? It could hold them until the end of time. This principle applies to domes, all of the force exerted on the struts is pulling, not squishing.
That's why I built this dome out of 1" (which is actually 3/4" in the real world) sticks, weak and many cracked. I wanted to see if they could hold up. More on the results of that later.
These are the most useful online tools I used:
Desert Domes has a number of great resources, the Dome Calculator and Reverse Dome Calculator being my most used. It is helpful for figuring out the length and number of struts, and number of vertices needed for different frequencies of domes.
Then I used this diagram during assembly.
Dome frequency is basically the number of triangles that exist in the dome. The higher the frequency, the stronger the dome, and the more complicated and more materials you will need. The one pictured is a 3v (frequency 3) 3/8 dome. The 3/8 means it is 3/8 of a sphere, so you can imagine just cutting the top 3/8 off a baseball, and that's what it will look like.
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http://en.wikipedia.org/wiki/Constrictor_knot
great job fella
Thanks!
http://www.desertdomes.com/bamboo.html
In this case a V3 dome is lashed using only two sets of 4 point vertices. Since all of your struts are components of your vertices, set up and construction consists entirely of preparing vertices and lashing those together to form struts already in place in your completed structure.
The whole design and measurement system is set up to build from the top down, as opposed to a bottom-up construction, making it easier to place and attach your covering as you construct your dome.
I wanted a durable, cheap, insulated covering, so I covered it with the cheapest thing I could find - a surplus Army parachute, stapled to every strut with furring strips. Then I used a commercial spray rig (my Dad's company owned it) to cover it with about an inch of spay on foam insulation, covered that with 3/4" mesh chicken wire, then another inch of foam. Let that cure a week, then painted it with asphalt mobile home roofing compound. It is still standing, on my brothers property, which frequently gets 18" or more of snow in winter.
Thanks!
My brother repaints the dome every 5 years or so, and he also sprayed the interior with Kilz epoxy sealant paint, and installed two bi-metallic coil thermostatically opening vents at the peak - those are still available, made for greenhouses. It is quire warm inside, even when buried under snow. He has a "dairy barn" type small electric heater in it.
I actually built 5 domes, in total, but only the one geodesic. The rest were experiments, and two of them failed pretty quickly. The other two stood up quite well, and one of them is still being used as originally installed - as the roof of a hay storage/stable which is 24' in diameter. We set that one on a frame that lifted the lower edge of the hemishere 8' feet in the air, while leaving the opposite edge 4" off the ground on framing.
At our local playground is a geo-dome play structure (old school style). what they did was take metal pipe and pinch the ends flat and put a bolt through the connections. ( they "finished" it with a large 4' washer on the outside).
So why could you not just do the same thing with PVC? That is , heat the ends, pinch them in a vice and drill a hole. The only hitch would be the "length" in the dome calculator would be the distance between the holes. This can be done with a simple jig. this would address the rigidity issue, and simplify construction.
Any thoughts?
The galvanized steel would make a super strong dome, but I didn't want to spend the money on it. My neighbor has some that we will be using to build him a dome though, so stand by for an instructable on that.
Thanks for writing!
I built a lot of crazy stuff with PVC (google Sam's Nascar simulator) but nothing that will get a lot of sun---
Some angle iron about 120 - 160mm over size, 3 holes - one to put a bolt into as the cutting stop, one as the locating pin, and on as the drilling location hole.
As long as they are all exactly the same length....
"Some angle iron about 120 - 160mm over size,"
Comma denotes a break. So let's look at this... Yeah, I know what angle iron is. What context you mean by "120-160mm over size" is anyone's guess. A Google for "120-160mm over size angle iron" isn't going to return anything helpful. By carefully pulling apart the sentence, I'm assuming you're saying the piece of angle iron is going to be the base of your jig and needs to be 120-160mm longer than the strut you're trying to make? But I can only guess here.
"3 holes - one to put a bolt into as the cutting stop, one as the locating pin, and on as the drilling location hole."
Where are the three holes going? The cutting stop for what? Sure you're making a "universal cutting AND drilling jig" but what are the bolts going into? The angle iron that's about 120-160mm over size? And what is the "locating pin", and the "drilling location hole" locating? And for which drilling?
Your sentence didn't make sense. Covo stated that. I'm stating that too. Getting snarky and saying, "WELL GO DO SOME RESEARCH" is not the appropriate response. I know you're good at being helpful when you want to be (I particularly liked your 'ible on using polyfill for a pool filter - will be doing that for my hottub once we get it running).
I would honestly be interested in knowing what kind of jig you're talking about, and how you picture it should be constructed. I would actually like to build one of these domes as a greenhouse.
http://www.rockler.com/product.cfm?page=11459&rrt=1
http://www.makergear.com/products/3d-printers
Thanks for the comment!
I use a hack saw with a carbide grit bar blade to cut away excess material from around the tenon, in a hex pattern.
Total cost for the hole saw, speed boring bit, and hacksaw bar blade, about eight dollars.
They are removable.
6 or 12 of them 40cm long 6 - 8cm diameter.
OK:
"Are you using organic wood or manufactured wood? If you use the manufactured wood it could leech wood products into your food and you might die."
Now the serious question.
It's a kind of "you get what you pay for" issue.
It's great to experiement, BUT after all the time and effort, will the results be worthwhile? Or with a little bit more of an investment in materials etc.. will it be a lasting product or a "epic failure" as it flys across the valley in bits, in the next storm.
It's untreated pine from my local lumber mill. I understand what you're saying, it's important to keep the food clean, and using a bunch of chemicals would defeat the purpose.
The results have already been worthwhile, just with the lessons learned. If I get to watch it get demolished in the next wind storm, I feel it'll be worth that data as well. It's late enough in the season that I'm thinking of just throwing some chicken wire over it and using it to keep livestock off some of my trees though, which means the big wind storm tests won't come until September. By then we'll have some more built out of bamboo and fabricated vertices, so if I suffer a casualty I'll update this instructables with pictures, and advice to make them bigger than 3/4". I think that'll be worth it too.
I was wondering if you could start assembly at the top. Ie build the top pentagon and then lift one side and add the next row etc.
I still don't like PVC too much, mainly because it's a permanent plastic, so we're going to try bamboo next. We've already got 6' pieces, which means if we built the exact same dome, it would be 28' across instead.
No I don't represent the company. Oh and it isn't cheap.
Thanks for the advice though, now I know where to go when I need super tape!