Fuller Dome - upper limit on size for v2?

typewriter · Post by **typewriter** » Fri Jun 11, 2004 3:33 pm

Looking at a 3/4" EMT v2 dome. The largest dome for the money seems to be a v2 with _very_ long struts, as in struts that could be up to 10'.

The question is this, can a v2 get that big realistically? I have no need to hang things or climb it. I am more concerned with a large area for people to dance and chill. This would be used for (hopefully) more than just bman. I want to do panoramic projections inside of my interacative visual synths.

The force of wind against cloth of that much area could create a fuck load of force.. But could it really trash a 3/4" aluminum frame?

Tiahaar · Post by **Tiahaar** » Sat Jun 12, 2004 12:06 am

Yes.

I'd be afraid the 10' long 3/4" conduit wouldn't be stiff enough to keep from buckling in the wind when covered with a tarp. It kind of bows just picking up one end of a piece that length...hmmm...but hell I haven't built one like that and I'm trying to imagine how it would fail. Would a whole hub and its attached struts push in? If the struts start to bow and can't transmit the compressive load then its all over. Where's my CE 301 Statics book?

Badger · Post by **Badger** » Sat Jun 12, 2004 2:51 am

ROT (Rule of Thumb) as I understand it is is never go more that 5' with your shortest length which puts you somewhere in the nieghborhood of a dome having an 8' radius.

DancingTofu · Post by **DancingTofu** » Sat Jun 12, 2004 5:35 am

I saw one HUGE dome in '02, at one of the rave camps at the 2 o'clock end of the city. I was rather....distracted, but my impression of it was 25 feet in diameter, quite possibly more. (My frame of reference is my house, a two level geodesic dome house, wood and plaster and everything. It's 25' across the living room. This dome, in my (quite possibly distorted memory) was even bigger.)

Not that that really helps, as I know nothing about how it was constructed or whether or not it collapsed 5 minutes later... But it's lonely tonight at work, and no one here appreciates my Burning Man flights of fancy.

--maudlin manda

Bob · Post by **Bob** » Sat Jun 12, 2004 10:38 am

http://www.pacificdomes.com/technical/engineering.html

Note the blank line for 60 ft dia w/ 3/4 in. tubing. One of those had some damage in a windstorm at Burning Man a few years ago -- had struts at least 6 ft long, I think -- it eggshelled partly because the skinny rebar stakes around the windward perimeter began coming loose, which allowed for a bit more flexing than it was capable of resisting. Looks like most of Pacific's dome kits use nothing longer than 5 ft. At ten ft long, I'd go for 1-1/4 in. pipe at least. A good rule of thumb might be to avoid struts of whatever material or size that would tend to fail in bending or buckling if used to bludgeon and hoist up a raver. If none are available, try a rabid coyote.

robotland · Post by **robotland** » Mon Jun 14, 2004 7:09 am

As an outside limit for 3/4" tolerance I use the max size of a 2V dome that can be made with struts of both lengths cut from the same stick- about 5'3" and 5'9".....that gives you about an 18' diameter dome. Even at a smaller size, the struts will bend if climbed on. I've stacked three 3/4" conduit 2V domes, (6', 12', 18') and had no troubles since all weight was directed to the vertices, but all it takes is for one section to fail and you're SOL.

typewriter · Post by **typewriter** » Mon Jun 14, 2004 1:06 pm

I refuse to be responsible when my dome collapses because some Jimmy Buffet-er who had one too many Mai-Thais and way too many hamburgers has a flash of Amazing Spider Man fever and brings down the fuller on my friends!

I guess my 30' diameter 3/4" tube dome was a pipe dream.

Why is aluminium so freakin expensive?! Can I blame Bush?

Badger · Post by **Badger** » Mon Jun 14, 2004 2:35 pm

And of course you've seen this link:

http://www.desertdomes.com[/i]

Angel Ben · Post by **Angel Ben** » Mon Jun 14, 2004 2:46 pm

I've just worked out the following for the best smallish dome for your money:

7'10" 5/8 3V, using 1/2" conduit.

I *think* 1/2" will be stable enough, because the longest strut is just over 3' long. Just don't let anybody climb on it, and don't hang anything heavy.

If you cut the struts like so:
30x ACC
20x BBC
5x BBB

You end up using only 55 pieces, which should only cost $200.

Since it's a 5/8, it will actually be over 9' tall, and the majority of the over 15' diameter will be usable since the outer walls are more or less vertical a few feet up.

My only real worry is whether or not it will take having a missing section for the door.

typewriter · Post by **typewriter** » Mon Jun 14, 2004 4:04 pm

Badger: yes I've been engrossed in filling spreadsheets and diagrams with dome calculator output ever since I stumbled upon the great desertdomes.com site.

Angel Ben : Be careful, because the structural integrity strictly depends on the presence of all the struts. There are ways around this, but I beleive they add quite a bit of planning and effort to your project.

robotland : I like your suggestion, 2 struts per stick, I was also considering that. I understand that this design would still not allow climbing, but would
we be able to hang a couple of skychairs / hammoks in that bad boy?

> cut from the same stick- about 5'3" and 5'9"

11' sticks eh?

Bob · Post by **Bob** » Mon Jun 14, 2004 11:38 pm

Seems to me that you might be better off in the long run with a structure suitable for climbing. I think the Death Guild's Thunderdome was originally a 45 ft Pacific dome w/ 3/4 in. conduit, and after a couple of years they bumped it up to 1 in.

Dork · Post by **Dork** » Tue Jun 15, 2004 12:22 am

and after a couple of years they bumped it up to 1 in.

A little bird told me the latest iteration had one piece of conduit inside another for additional strength with all of the yahoos climbing on it. I don't know if that's true or not, but it sounds plausible.

Badger · Post by **Badger** » Tue Jun 15, 2004 12:27 am

A little bird told me the latest iteration had one piece of conduit inside another for additional strength with all of the yahoos climbing on it. I don't know if that's true or not, but it sounds plausible.

Seems like slipping in a piece of rebar might reinforce the hell out of the dome. With Thunderdome being as huge as it is I'd probably want an assessmnet made as to whether or not the struts could support the combined weight of the dome and the rebar.

Bob · Post by **Bob** » Tue Jun 15, 2004 12:39 am

WTF are you two drinking?

robotland · Post by **robotland** » Tue Jun 15, 2004 5:32 am

typewriter wrote:> cut from the same stick- about 5'3" and 5'9"

11' sticks eh?

......uh, ooops. Let's make that,"about 4'3" and 5'9""......Sorry to be Ministry Of Disinformation!! Typewriter, you can ABSOLUTELY hang some hammocks and stuff from a 2V 3/4" as earlier described.....The structure that I mentioned was in Hushville last year, and at peak traffic had eight or nine people on deck. (Literally- I made a custom platform by adding radial supports from the "North Pole" and covering them with wood.) If you can hang from any vertex and get movement, you've got a loose bolt somewhere! One of the amazing (to me) things about domebuilding is that magic moment when you make the final connection and suddenly a wiggly heap of tubes springs into shape and becomes an amazingly strong structure. Satisfying!
As far as putting stuff inside- I have tried both conduit and rebar, and was very disappointed with how little it helps. I suppose using GASPIPE or THICKWALL conduit might work, but it's so danged HEAVY!

If there's construction around where you are, check the dumpsters if you can....I routinely pull conduit out of construction sites, although the workers may start salvaging it like they do the scrap copper, given the cost of steel these days....It IS steel, BTW, NOT aluminum.....

......Those lengths again, 4'3" and 4'9"........

Angel Ben · Post by **Angel Ben** » Tue Jun 15, 2004 7:31 am

If you actually want a "big" dome, I think the closest thing to a realistically affordable design would be a roughly 11'10" (11.823', specifically) radius 3/8 3V. You can cut any combination of 2 struts out of a single piece of 10' (the "C" pieces are exactly 5' after adding 1.5" for drilling).

The 3/8 would cost you about $420 in conduit, or $580 for the 5/8. That's probably about the biggest you can go with 3/4" on a 3V, without having prohibitive amounts of waste.

Bob · Post by **Bob** » Tue Jun 15, 2004 7:35 am

robotland wrote:As far as putting stuff inside- I have tried both conduit and rebar, and was very disappointed with how little it helps.

The only way rebar adds anything inside a tube is if you follow it with concrete.

robotland · Post by **robotland** » Tue Jun 15, 2004 8:02 am

Well said, as usual.

typewriter · Post by **typewriter** » Tue Jun 15, 2004 1:52 pm

How many rebars are more than enough for stakin er down? Will 1-2 per 'ground strut' be burly enough?

robot, I'm trying to picture your platform. When you say radial supports from the pole, do you mean a disc sitting on top, outside the dome? If so, what was supporting the edge of this disc?

I'm beginning to think designing and planning might be my favorite part of the whole thing..........

Angel Ben · Post by **Angel Ben** » Tue Jun 15, 2004 2:42 pm

typewriter wrote:I'm beginning to think designing and planning might be my favorite part of the whole thing..........

Heheh, seriously, I'm beginning to consider not going so I can use the ticket and airplane money for a bigger dome ;)

typewriter · Post by **typewriter** » Tue Jun 15, 2004 3:42 pm

As long as I'm asking, why are carriage bolts reccomended? It seems like they would be harder to tighten, and even harder to disassemble, given the round heads. Why not use a hex bolt?

Bob · Post by **Bob** » Tue Jun 15, 2004 6:15 pm

Re: stakes, as with anything, depends on the size and geometry, and what needs to be staked. At least one at each vertex that touches the ground to pin the frame in place, and a bunch around the perimeter for the covering, but your experience may vary.

gatonegro3 · Post by **gatonegro3** » Thu Jul 08, 2004 7:36 am

How about a 2v dome out of 1" conduit with 10' struts, if you reinforce it by running a line from each vertex to each strut midpoint?
I have read this somewhere, and seems to make sense. The lines would keep the poles from flexing (you would have to break the line to flex any pole, i think) That should change something. Anybody has experience with such a construction?

I'm having height-anxiety dreams because I might be sheltering my whole camp under a 2v dome with 10' struts. In addition, I want to build an Attic (the ecstatic-attic, by hanging a round fisherman net along a "northern tropic" so that I get sort of a mezzanine that you can (gulp) jump in. PLUS, er...hammocks. (FIVE of them???)

The best part, is that if I hadn't ran into you guys, I was going straight to playa without even testing the dome back home. Would have probably lost all my friends and head off north covered in puke and playa dust (typical punishment at my camp)

gatonegro

robotland · Post by **robotland** » Thu Jul 08, 2004 9:08 am

The lines would help support your covering, but structurally would only restrict movement back and forth. Okay, they'd help with in and out A LITTLE. But not much.
I regret being unable to post a snapshot of this due to my own technological ineptitude, but I'll try to describe how I reinforced my Snowman triple dome.....

I put a wooden deck on Level II of the Snowman for BM 2003, and had worried about load on the middle of the struts. (2V, 5' rad., sitting on top of a 2V 9.5' or so rad., with a little 2V 3' rad. on top!) The deck sat directly on the bottom dome, upon nine struts that radiated from the North Pole of the bottom dome. The struts were 3/4" conduit, just like all the rest of the Snowman, and they were reinforced with 2x4"s clamped on with two 3/4" conduit clamps apiece. The decking was nailed onto these 2x4"s, and consisted of 2x6" scrap lumber cut to make a deck like a pentagonal picnic table. There was one triangle of the pentagon left open, corresponding with the one strut left out of the support structure, for the ladder.
I'll give you ALL the details if you want, but what I'm getting at is that I reinforced with rigid sections of conduit, which constrained the movement in more than one direction. Leaving one out didn't even seem to be noticeable. I even left the whole top pentagon out of the middle dome after smacking my head on it every two minutes. Negligeable effect on integrity, but I'd put those five struts back in if I planned to climb on the outside of domes 2 and 3.
A ten-foot strut just scares me, especially if you're hangin' stuff on it and from it. If you've got 400 bucks to throw down for the conduit, maybe you should spend half of that again and buy 2x4"s and clamp 'em on. I'd STILL test it pre-playa.

Burp! · Post by **Burp!** » Thu Jul 08, 2004 5:19 pm

We built a F3 dome (Smoochdome) last year, 30x15, had hammocks and had no problems.

In 2000 our F2 dome, same size, caved in when the winds got rolling. We made the mistake of putting a balloon covering on it that year and not having vents and a plan to bring it down quickly if trouble came calling.

There was a dome like ours right next to us that year that had a custom cover that was form fitted. They has no problems. The key is not having a cover that will catch wind and hold onto it. The f2 dome was pretty strong as I remember, we had several hammocks an never saw a buckle.

NoFlash

Burp! · Post by **Burp!** » Thu Jul 08, 2004 5:47 pm

My Bad.

Dome I (2000) was a Frequency-2 class-1 design.

Dome II (2003) is a Frequency-4 class-1 design.

http://www.colorado-research.com/~gourlay/dome/hiFreq/

NF

gatonegro3 · Post by **gatonegro3** » Thu Jul 08, 2004 11:33 pm

Hey Burp!
How long were the struts of your f2 dome?
and how thick was the conduit?

Robotland, are you SURE of what you are saying about the lines going from vertexes to middle of struts not being of much help? to my very basic understanding, that would keep poles from flexing, reducing the length to a virtual half (about 5') How can they bend if they are tensed to both sides? If they want to bend outwards, the line would tense and keep it, same thing inwards, and obviously sideways. It would (in my dyslexic mind) translate forces from poles to vertexes. no? yes?

Please! post a pic. We all want to see your fab snowman. We trust you with a dome, we trust you with a jpg.

gatonegro

Bob · Post by **Bob** » Fri Jul 09, 2004 6:31 am

On the playa, I'd err on the side of overbuilding rather than underbuilding.

robotland · Post by **robotland** » Fri Jul 09, 2004 7:40 am

typewriter wrote:robot, I'm trying to picture your platform. When you say radial supports from the pole, do you mean a disc sitting on top, outside the dome? If so, what was supporting the edge of this disc?

....

....I missed this inquiry when rereading the posts! The edge of the disc (more like a spider's web, really) was supported by the secondary dome- the nine (out of ten) struts that radiate from the North Pole of the primary dome connect to the vertices at the equator of the secondary dome. In order for them to do so, the flattened ends of the struts had to be bent upwards 90 degrees. I made some kinda tricky couplers to connect the two lower domes, since they weren't initially designed to connect smoothly, but the junction of the two UPPER domes was somewhat more premeditated and went more smoothly. Having Tara's Desert Domes dome calculator to play around with helped IMMEASUREABLY.

robotland · Post by **robotland** » Fri Jul 09, 2004 7:51 am

gatonegro3 wrote: Robotland, are you SURE of what you are saying about the lines going from vertexes to middle of struts not being of much help? to my very basic understanding, that would keep poles from flexing, reducing the length to a virtual half (about 5') How can they bend if they are tensed to both sides? If they want to bend outwards, the line would tense and keep it, same thing inwards, and obviously sideways. It would (in my dyslexic mind) translate forces from poles to vertexes. no? yes?

.....I just think it'd have to be tightened to an unrealistic degree in order to be helpful. Furthermore, those lines would have to terminate somewhere and once you reach the ground-struts it "stops being geodesic" and becomes half of something that derives its ultimate stability from being WHOLE (a sphere). While you might be able to park a Geo Metro on the deck of my Snowman, you can squash it out of round and precipitate its collapse just by pushing hard from the side!

Please! post a pic. We all want to see your fab snowman. We trust you with a dome, we trust you with a jpg.

....Thanks for your encouragement! I'll try to crack this nut and get some pics up.....Any (non-technical) suggestions on how to get pics into here?

Fuller Dome - upper limit on size for v2?

Fuller Dome - upper limit on size for v2?

big 2v

Domes n Stuff

Domes