Question about dome construction

Dato · Post by **Dato** » Mon Jul 10, 2006 1:38 pm

Hey guys, new here... Was looking through the other topics on geodomes, and see that there are quite of few experienced dome builders here, so figured I'd give it a shot. I looked throught the other topics, and didn't see what I needed, but I did search. ;)

I got all the calculations for this thing off of desertdomes.com, but have a question about exactness...

I was initially going to go with a 5/8 3V12' dome, but realized the lengths of the "C" strut with the extra 1.5 inch allowance were going to put me over 5 feet. To conserve pipe, I really wanted the "C" struts to be 5' even. This way, the pipe could be cut exactly in half to make 2 C struts a piece. Running the reverse dome calculator, I found the right R to make it work. Once we started cutting, I realized that I did not account for the 1/8 inch that is the width of the blade making the pipes slightly off. Does the 1/8 of an inch shortcoming on some of the pipes mean I'm doomed? If not, how much of an allowance for error is there? Thanks in advance for the help!

capjbadger · Post by **capjbadger** » Mon Jul 10, 2006 2:13 pm

The truely critical lenght is the distance bewteen the holes in each struct. Basicly your 1.5in buffer area on the ends will be a little smaller. Its the distance between the holes that matter. As long as that distance is right, you'll be ok. The only other factor to keep an eye on is make sure the hole doesn't get too close to the side or end edges. Domes try to pull apart at all times, so if the hole is too close to the edge, you may have a failure.

Needless to say, make sure you have some spares of each strut size with you in case of one getting bent, broke, etc.

Also, the higher the freq. of the dome, the less "wiggle" room you have on the measurements since the higher freq. dome have more struts and thus and errors are magnified even more. A builder of a one or two freq. dome can get away with things a builder of a three or four freq. dome couldn't.

Dato · Post by **Dato** » Mon Jul 10, 2006 3:06 pm

Cool. thanks! I figured the 1/8 of an inch shouldn't be a problem if the holes were drilled correctly, just wanted to make sure before I cut the rest of the piping. I just didn't want to end up in a situation where I got to the very top, and the last few pieces didn't fit.

And yes, I'm bringing plenty of extras, so I should be ok.

Dork · Post by **Dork** » Mon Jul 10, 2006 3:45 pm

Yup... 1/16" off each bar is really not going to be a problem. The danger is with errors compounding. Cut 1/4" too short, put first hole 1/8" too far in, making the second hole really close to the edge.

Build a jig for cutting the pieces, center punch all holes before drilling, build another jig for cutting the second hole. It will be fine.

It's probably a good idea to cut/drill the longer pieces first, too, so if you do mess one up it can become a smaller piece.

Dato · Post by **Dato** » Mon Jul 10, 2006 4:11 pm

Yeah, I have a jig for cutting, but it's really hard to avoid the 1/8" type of errors. 1/8" Doesn't seem like much, but like you said, I'm afraid of them compounding. And I am going with the bigger pieces first, since it's the easiest part. Each 10foot section just gets cut in half. hehe

And I'm most def building rigs for pressing and drilling. I figure I can make those more precise than the cutting. I suppose we'll see when it comes down to it.

timber mischief · Post by **timber mischief** » Mon Jul 10, 2006 5:48 pm

The reason you want 1.5" on each end is to put the center of your hole at 3/4". You will need equal flat space on either side of the hole. Too little on the inside of the strut means your connections will not lay flat. You could use longer bolts in that case but you will lose all structural integrity. Do a trial run and bolt together the first 6 poles you make. It can save the headache of re-pressing them.

robotland · Post by **robotland** » Tue Jul 11, 2006 5:51 am

My Wise Colleagues have already covered the principal salient points, but allow me to add one: Before heading out, do a trial run. On a flat surface. Hell, you were probably going to, anyway.
If you run into a little "snugness" because of the minimal error margin, having a couple of tools can make assembly LOTS easier- First of all, having another set of hands is the best. A pair of long-nosed visegrips is pretty damned nice, too. And a stepladder- Not even a very big one, but a STURDY one with big feet. You could even screw scraps of 2x4 onto the feet, just to make them more stable. Or, at least scout the whole "foundation" of your dome to make sure there aren't any soft spots that you could sink a ladderfoot in and give yourself a nasty spill. (Believe me, even a short fall on playa can hurt like hell.) I found a great little "folding step" at an RV store- Just a single step, about a foot tall, but it came in SO damn handy for dome-fiddling and cartop-fussing.
Personally, I'm giving myself a vacation from domes this year thanks to a neck injury...Well, that is, I'm BRINGING one....but it's made of cardboard tubes, and if it gives me ONE BIT of trouble, it goes on the nearest burn platform.

Dato · Post by **Dato** » Wed Jul 12, 2006 10:11 am

cool. Thanks! And of course I'm planning to do a trial run!!!! it would be a bit, errr, stupid to build something like this for the first time, and not make sure it it works before heading out ot the playa. =) Besides, I want to see the thing built!

I emailed Tara at desert domes with the same question, and she had the same response, so I kept on cutting. Problem now, is that the blade on the saw I was using is getting shaky, and taking a bit too much off the pipe. I'm picking up a new one today, and hopefully finishing up the cuts this evening or tomorrow. Pressing, drilling and bending should happen this weekend, so hopefully it will be ready for assembly early next week.

Then..........on to the cover.

capjbadger · Post by **capjbadger** » Wed Jul 12, 2006 10:17 am

Not sure what kind of cutter you are using. I used a jig saw with a metal cutting blade. I'd have to retighten the screw that holds the blade straight now and then. I think I went through two blades cutting it all.
Oh, and make sure you keep some oil on the blade. I would take a little model paint brush and "paint" a little oil on the blade before each cut. You blades will last much longer.

DoctorIknow · Post by **DoctorIknow** » Wed Jul 12, 2006 11:03 am

Dato wrote:....Pressing, drilling and bending should happen this weekend, so hopefully it will be ready for assembly early next week.

If you're using a real press the advantages and disadvantages are covered extensively somewhere in the eplaya. (forget about even the biggest vice, I tried a huge one once and BUSTED it!) Seems even 5 ton hydraulic presses have quit in what one would think would be an easy job for them. I believe most dome builders here using conduit use a 3 pound hand sledge...get friends to help pound while you run the drill press (Don't even think about using even a powerful hand drill! Buy a $89 Chinese drill press from HarborFreightTools : http://www.harborfreight.com/cpi/ctaf/d ... mber=44836

One can use a concrete floor to pound against, but I wish I'd bought an anvil for $49 :
http://www.harborfreight.com/cpi/ctaf/d ... number=806

Pressing or pounding, IF your conduit is like the stuff I used, it is a piece of steel folded on itself, with a seam. Sometimes that seam isn't visible as they smooth it out, but it can be VERY visible if you pound it so the seam splits open. If it happens to split open on the side of the new ends you've just pounded, it can be razor sharp, and to fix that requires one more step in this process that, for me, took 5 times longer than I ever anticipated.

So, make sure that seam is in the middle of your flattening process!

And don't forget to pick up as many spray paints (day-glo, of course) as you have lengths of struts! There will be considerable oil on the ends from drilling, so get some acetone to wipe 'em clean before spraying....

Good luck!

Burp! · Post by **Burp!** » Wed Jul 12, 2006 11:50 am

Once you get going and are starting the building process, I have found that a key tool to have and to have many is a good cordless power drill, have many charged batteries waiting as well. Hand ratchets are ok, but a good drill gun will help pull ends together when things get tight. Typically when you bring 3+ vertices together, they don't want to cooperate and slide down to the bolt head, if you can get the nut on to the bolt, the drill gun can screw it down easily, making quick time.

You will need to get the bit that will take a standard socket, not always something people have in their toolbox, get several so you can have lots of guns going at once.

T.

Dato · Post by **Dato** » Wed Jul 12, 2006 2:32 pm

For the pressing, I was planning to use either a 3 or a 5 ton hydrallic press, I figure it should be ok. I do have a drill press for drilling, and a few cordless drills for putting it together.

As far as the seam, eveything else I read said I should keep the seam at a 45 degree angle to minimize slplitting. Did you get any splits going down the middle?

For the saw, I am using a circular skil saw with a 7 1/4 inch blade. It works well, but the problem is, the thing is old, and no matter how much I tighten it, it is still a bit loose. Loose enough to take off an extra 1/8 of an inch in addition to the 1/8 of an inch already taken off by the blade itself. I'm running down to home depot after work today to grab a new one, so that should be resolved. Then back to cutting until late at night or until I get yelled at by neighbors, whichever comes first.

Thanks again for your help guys.

Oh, and what did everyone use for a cover? I don't particulary want to use tarps... I was thinking painters dropcloths sewn together into a one piece cover made of triangles. I found designs for similar covers online, was just wondering if the dropcloths would do the trick.

capjbadger · Post by **capjbadger** » Wed Jul 12, 2006 2:51 pm

A 5 ton press was just enough to press my 3/4" EMT. If it had been larger than that, I would of looked around for a 10 ton one. This is of course after snapping a vise in two... doh

Oooo... 1/8th plus another 1/8th.. 1/4". bad...

Hahaha... I so know the whole "I know I can get away with banging the shit around for another 15 mins before the neighbors yell at me....
Again..."

Tarps can work. Its just a bitch trying to wrap a rounded object (the dome) with a flat object (the tarps). Tarps and dropcloths will both run into the same issue. Sewing up a custom cover is cool if you have the time. I used tarps last year (silver ones) and they worked quite well once I got them all tied on and snug.

I would advise getting a few lenghts of that pipe insulation foam. Cut it into short bits and tie it over the points where the bolts are. Your cover will move back and forth over those points and wear holes in your cover if you don't pad them somehow.

Burp! · Post by **Burp!** » Wed Jul 12, 2006 4:18 pm

cover option: see my post in this thread http://eplaya.burningman.org/viewtopic.php?t=13450

Dato · Post by **Dato** » Wed Jul 12, 2006 6:10 pm

badjer, that sounds good. mine is 3/4" as well, so I guess a 5ton should work.

Tarps are a last resort, but I would really love to sew up a custom cover. If I finish the hardware portion by this weekend as planned, it should give me a month and a half to work on the cover. And thanks for the foam suggestion, I was wondering about that.

Burp! I saw the other thread, and love your guys' dome. Problem is, mine is going to be my house as well as my hang out spot, so I can't really have it wide open.

My plan for the cover was to use falk's idea from here (http://eplaya.burningman.org/viewtopic.php?t=13355). It will cover the dome in it's entirety. One of the seams will not be sewn, but instead have clips, giving the ability to close it when needed, or open the flaps for ventilation during the day. For sleeping arangements, I was planning on putting a small tent in the corner. Wait, what corner?!?! haha Anyway, you get the idea. We have a generator and some fans, so that should help quite a bit for ventilation. In any case, should be a whole lot better than my 10x10x7 unventilated pvc structure from years past.

As far as putting the cover together, I was thinking of designing and cutting the pieces myself, but for the actual sewing part, taking the plans and material down to a sewing shop, and having them put it together. And experienced clothworker (or two) with an industrial sewing machine should be able to do the job in a day.

Dato · Post by **Dato** » Sat Jul 15, 2006 5:55 pm

Whew.

No press for me. Went all over the place, and could not find one for rent. Got a 10 pound sledge hammer instead. With 3 people rotating doing 10 pipes at a time, we only got through a bout 80. Man, that's a hell of a workout in 90+ degree heat! haha

Problem with the sledge hammer is that even though we have a jig built, the flat ends are not exactly the same length on all the poles. I figure if we drill the holes at the same distances from the edge, we should be ok.

I'm beat. More tomorrow. Hoping to have this thing up or miserably fail by next weekend. :)

LeChatNoir · Post by **LeChatNoir** » Sat Jul 15, 2006 9:44 pm

I figure if we drill the holes at the same distances from the edge, we should be ok.

I'd say you figure correctly. And you gotta love that hammer work out, huh?

robotland · Post by **robotland** » Sun Jul 16, 2006 8:16 am

Just thought of something else...You might want to bring some eyebolts, to hang things from like hammocks and such. I usually brought an extra, lighter-weight hammock to use as "guest bed" in a pinch, but primarily as extra storage. Getting stuff up off the floor is darned handy. When buying them, make sure you don't get them with threaded parts that are too long, as they will stick and menace your cover unless covered themselves. This CAN work to your advantage in one way, however- Sometimes, that last couple of five-or-six-way connections can be hellish to tighten down. Using a long-shanked eyebolt can allow you to get all of your struts loosely connected, for easier tightening afterwards. And you can stick a wrench handle through the loop for leverage.

Tiahaar · Post by **Tiahaar** » Sun Jul 16, 2006 10:38 pm

robotland wrote:Just thought of something else...You might want to bring some eyebolts...

Love that, my very first dome build happening this year & gonna put eyebolts all around. Hey something that worked well for me today was putting to use an a-frame press from HF (really affordable) that has been collecting dust in my yard. When I bought it for doing wheel studs on an axle I managed to break one of the press plates, so I ordered another set of the 12 ton plates and a set of 20 ton plates (also really affordable). The replacement 12 ton plates have various notches and semicircle indents around the outside and one size is PERFECT for squishing conduit with that neat curved flat end. The plates are cast iron so not weldable but I bolted a steel bar to the top plate then welded that to the press rod. Viola! The jack presses the two plates together to squish the conduit and the retraction springs have enough power to pull the jack and the one plate back up for the next piece. One of the 20 ton plates sits underneath for supporting them, hard to see it clear in the photo. Did 60 squishes today no problem, this is so cool! Tomorrow will drill and bend (doing a 1v full sphere with 30 5' struts of 3/4" EMT. (and hey how come nobody out here stocks that awesome "True Color" EMT by Allied that comes in six or so colors???? I really wanted some yellow)

Dato · Post by **Dato** » Thu Jul 20, 2006 11:12 am

score! No more hammering for me. Found someone yestarday with a 20 ton hydraulic press. :D Did about 90 squishes yestarday without a problem! Hoping to finish the squishing tonight, or tomorrow evening at the latest. All day saturday will be spent drilling and bending, so hopefully I'll see this thing set up on sunday. Man, I can't wait. Thanks to all you guys for your help!

Tiahaar · Post by **Tiahaar** » Thu Jul 20, 2006 1:47 pm

Awesome!! Gotta love hydraulic presses.

To recap, the critical thing is that the drilled holes for same-size struts are spaced exactly the same distance apart. (if the strut lengths vary a tiny bit the holes may be a bit closer or further from the ends...but as long as they're the same distance apart with enough flat to bolt tight things will work! I am now addicted to domes!) I used a board clamped to the drill press with a locater pin in one end like shown on the desertdomes site and it worked nicely.

(look at me....build one little dome and think I'm a pro heheh. But I do know of cases where the holes ended up in the wrong places!)

Dato · Post by **Dato** » Thu Jul 20, 2006 10:23 pm

Whoohooo! Done pressing! It's amazing how fast it goes with a 20ton press once you have a good jig and a system worked out.

The holes are next. We're taking tomorrow off, and *hoping* to finish up on saturday. We have all day and all night to drill, so we'll see if we can make it work.

I know about the hole distance, and am slightly worried about messing it up. I figure we should be ok if we use the ideas off of desert domes, but it's still a bit scary. It's nuts building something like this without any way of telling if you are doing everything right until the very last moment. I guess I'll just double and tripple check the calculations and cross my fingers.

The pipes are actually pretty damn close to the same size. Some are maybe an 1/8 of an inch off, but most are dead on.

We smashed a little extra on each side, figured it wouldn't hurt. There is about 1.5 inches of flat on each side, which should help with assembly.

If we get this thing up on sunday, I'll definately post up some pics. Wish me luck! haha

Dato · Post by **Dato** » Mon Jul 24, 2006 12:46 am

HAHA! It worked! It workkkkeeeedddd! Quite the amazing feeling when the last strut falls in place. We drilled and bent for 14 hours yestarday in a garage, in 110 degree heat. instane. But this.....this definately was worth it.

I'll post up more pics tomorrow, but here's one of me just finishing the last strut!

DoctorIknow · Post by **DoctorIknow** » Mon Jul 24, 2006 7:42 am

Good going! Took 5 times longer than you planned I bet. Mine took 10 times longer LOL...

What is the diameter?

timber mischief · Post by **timber mischief** » Mon Jul 24, 2006 8:21 am

Nice job and good ladder saftey skills! After you take it down, have a few PBRS and a "saftey Meeting" then put it back up for that more authentic playa experience. From the pic it looks like a 23' 3 freq.

Tiahaar · Post by **Tiahaar** » Mon Jul 24, 2006 9:16 am

SUPER!!! Smart too, I see some spare struts were made just in case!

Dato · Post by **Dato** » Mon Jul 24, 2006 9:31 am

Yeah, it's 24 feet in diameter, 3v 5/8ths dome. And yes, plenty of extra struts...never know what can go wrong!

Oh, and at 15 feet tall, you either need ladder safety skills, or a good health insurance. hehe.

Here's the funny bit. We double, tripple and quadruple checked alllll the cuts, bends, hole distances for drilling to make sure everything was within an 1/8 of an inch. All these calculations were great. We didn't however realize that you can't put together a 15 foot tall dome with a 6 foot ladder.

The ladder in the picture is incredible, but that damn thing was expensive. Cost me more than the conduit. But on the bright side, when folded up, it fits into the back of my 2 door focus. Along with all the pipes, hardware, generator, and room to spare. Not bad...

And thanks all you guys for the help!

DoctorIknow · Post by **DoctorIknow** » Mon Jul 24, 2006 10:35 am

Looks like a Little Giant ladder....

I don't have a pic of my ladder "rig", but for just a few more $, you can add wheels to the ladder and have an ULTRA long, but narrow, trailer to haul shit from truck to camp, or with a bike attachment, a trailer for the playa. (More than one person on the ladder is a bear to pedel around, however!) But perhaps the most useful attribute is to just move the ladder around camp while setting up...just tilt it and move it.

Take the first rung closest to the ground, insert continuous thread rod, actually, the threaded rod you need will fit perfectly in the bearing of wheelbarrow wheels, then add one nut on each side of the rung (nyloc nuts, with huge washer, of course, put on the wheel on each side, then add the other nut (those chromy nuts with the rounded dome head). Harbor Freight Tools has lots of cheap wheels, but there will be some at HomeDepot, too.

BTW, the only strong chain and lock I have for BM is for the ladder I have...

Dato · Post by **Dato** » Mon Jul 24, 2006 9:36 pm

Here's some more pics in case anyone is interested.

I took these from a post I made on another forum I'm on, and am too lazy to edit. I hope you guys don't mind. :p

So, after a couple of years of trying various PVC structures and motor homes (wonderful, but expencive, and kinda defeat the purpose. hehe), I finally decided to build myself a geodesic dome. I've wanted one for years, and finally made the decision to do it.

So......first things first. What the hell is a geodome? It's a sphere made out of triangles. Or, in other words, as strong of a structure as you can get. http://www.desertdomes.com was my starting place, as she has great info and instructions on building any kind of geodome, small to humongous.

Ok, so now, how big? I decided to go with a 24 foot diameter, 3v 5/8s dome. 5/8s as in, it's not quite a half dome, but rather 5/8 of one. That means the dome goes outward first, before going in. This makes it over 6 feet tall as soon as you step in, giving you the most living space. Since I'll be living in this thing for a week, that's a good thing. Also, this gives me a little over 400 sqft of floor area, which is damn near the size of my apartment.

Ok, so materials. I needed about 800 feet of EMT conduit pipe. Make that 900 so I can have some extra pieces in case some get bent. Luckily I found a guy on craigslist getting rid of a bundle of 1000 feet for half the price I would have gotten 800 for at home depot. (they come in 10 foot pieces). Ok. Done. now what?

The 10 foot pipes need to get cut into 3 different lenghts, get about 1.5 inches of the ends squished, drilled at precise spots (within 1/8 of an inch. eek), color coded, and bent. Bent, because you just can't make a circular structure out of straight pipes. :p

Ok, so off we went.
The cutting and measuring:

Smashing the ends. We tried the 10 pound sledgehammer aproach, but that was insane, so we found someone with a 20 ton hydraulic press. Much, Much better. Don't have too many pics from that part, but here's out jig:

Once all cut and smashed, it was time to drill the holes. the drill press was a godsend.

Being the goofy bastards we are

This turned out kina cool. Through the fan:

Here's the cutting jig:

On to the color coding. The struts are pretty close in length, so color coding is important:

Bending:

Gotta love the hatch!

Ok. Done! Now, it's time for judgement day. During these 40+ hours, we had no idea whether this thing would come together. You don't find out until the last strut is in place. scary ****, I'll tell you that.

So, headed up to a friends property in the mountains to set up. The focus fit all the pipes, all the hardware, the generator, the speakers and the ladder. haha.

One funny bit. We double and tripple checked the measurements to make sure we were within 1/16 of an inch of the desired lengths, but nobody ever considered the fact that you cannot put together a 15 foot tall structure with a 6 foot ladder. So, I had to go out and buy this insanely expensive extendable 12 footer. Anyway, you can't have a build without beats, so......

Oh, yeah, it was 110, so we're not wearing shirts. If you're offended, do not continue.

level1:

level2:

going for 3:

ALMOST there!!!!

BTW, this property is incredible!!!!

At the peak! Is it gonna fit?!?!?!?!?!

YES!!!!!

Here's how the joints work:

Final tightening:

And, like I said, this thing is REALLY solid.

Happy me hanging out on top:

And my buddy sitting on the peak:

Well, that's all of it.

the cover comes next. It will be made of tirangles sewn together to fit over the dome in one piece. The top will have a small open circle with a solar fan, and there will be a big opening for a door that can open and close. The outside will be painted like a brain, and the inside will be separated into two rooms. 1/4 of it will be the sleeping area, and the rest, the living room. I have a couple sets of speakers, extra (designated just for this) dj equipment, and some lights to light up the inside. I'll post pics as all this gets done.

P.S. Above the doorway will be a Marley quote. "My home is in my head". And, since the playa is lacking, the speakers will be pumping reggae/dub/psy dub/downtempo all week.

timber mischief · Post by **timber mischief** » Tue Jul 25, 2006 12:11 am

DON'T SEW TRIANGLES !!!!! As you look at the last pic. You will see hexagons and pentagons. All the heaxagons meet on thier upper half's. So, lay out struts for half of a hexagon on top of your fabric. Measure out an appropriate seam allowance. repeat, then sew two halfs together. Now you have the equvilent of six triangles from two pieces of fabric. Also, all domes start with a pentagon on top, you can use the same process there, eliminating extra sewing. You'll still have to sew a few triangles. But, not as many.

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