Geodesic Dome Construction (Tips and Tricks)

[robotland]

I was considering lightening my conduit load by replacing the topmost dome of the Snowman with PVC- I found that 1/2" rigid PVC (the gray kind with one flared end, used as electrical conduit) fits nice and snugly into 3/4" EMT, so I plan to make hybrid struts of plastic with metal ends. Should lighten that dome by 2/3. In making a prototype I noticed that the EMT needs to be deburred or round-filed to allow the PVC to slide in, and that cutting with a pipe-cutter leaves a lip that has to be flared out, but with clean ends it fits together very satisfactorily. I then drill a hole and pop in one 3/16" rivet on each end to stop creep or rotation. Not for climbing, but great for shelter! I may even make a geodesic umbrella now!

[robotland]

PVC UPDATE #1 (Here we go again)
You really, REALLY do NOT want to try fitting 1/2" PVC into 3/4" EMT that you've cut with a pipe cutter. Getting rid of that lip was @!#!!. Cutting with a hacksaw or metalblade circular saw and then filing the burrs is annoying, but EASIER. It'll be interesting to see how my patience holds up closer to 65 of these....

[Martiansky]

Pictures Robo....must have pictures!!

[robotland]

Workin' on it. So far, I can only email them. I seem to be either 30 years too YOUNG or 30 years too OLD to understand what I'm doing on a computer.

[LostMachine]

Getting rid of that lip was @!#!!.

Robot I needed to debur a lot of stuff once the cheap solution I found was a step bit for a hand drill. It works great. It even flanges the end a little.
Home depot has them.

[Zulegoona]

Why not just use a heat gun to flatten the PVC, use a jig as simple as a hole drilled through a 2x4 to make the amount of pipe you heat consistent and another jig to squish and hold the end till cool. It would be a lot of work but seems like it would still be less than dealing with the PVC and the conduit.

[Isotopia]

Flattening PVC with heat and a vise is gonna give you cracks. Make no mistake.

[Zulegoona]

I've thermal formed PVC pipe and sheet stock as well as welded it with a plastic welder and haven't had a problem with it cracking.

Just get it hot enough it's got to be rubbery soft.

[iamtonynyc]

how many people would it take to erect a 24 foot dome?

[Isotopia]

how many people would it take to erect a 24 foot dome?

You can probably get away with two people in a pinch. Make sure you have a sturdy ladder.

[Isotopia]

I've thermal formed PVC pipe and sheet stock as well as welded it with a plastic welder and haven't had a problem with it cracking.

I was thinking the message was about heating and flattening/pinching. I guess it really depends on the width, stress, and 'V' type one's going for. V2 would not be a good idea to try to make by heating and pinching-especially if your struts are going to be longer than, say, 3.'

I'll defer to Bob's opinion of it though.

[Elemental666]

Workin' on it. So far, I can only email them. I seem to be either 30 years too YOUNG or 30 years too OLD to understand what I'm doing on a computer.

aww shucks buddy, I'll put em up for you, send em my way and I'll help you get them on the forum

[preburnkentucky]

O.K. I have the frame completed. 3v 8ft R 5/8.
The Vinyl i am using for a cover is discarded Billboard covers.
Anyone got the skinny on how to seam this stuff without a
needle and thread?
Two options I see are
chemical weld (but what solvent works best)

and Heat weld (how hot and how large a butt seam)

All suggestions are appreciated

[Elemental666]

I was going to go with a contact cement type solution on my canvas, cause I"m too lazy to sew. I'm sure there is a nice specific solvent for vinyl to vinyl to welds tho. Measure thrice, cut once, do you work on a FLAT surface and all should be good to go I'd think. But then I'm still working on my frame...

[preburnkentucky]

Especially when drilling, cutting oil is ESENTIAL.
Took 3 bits to do 1st hole in all struts, then happy hardware
guy recommened cutting oil. 1 bit did the other 195 holes!
oil with a champher bit does a great job of deburring as well.
And to reiterate others comments don't bother with the 1/2 inch
EMT. Already bent 3 struts;(

[robotland]

Great tip on the stepped bit-deburring....I use a 1/8" to 1/2" stepped to make my strut boltholes, and had considered getting a larger one for misc. projects but hadn't wanted to throw down the 35 bucks for a decent one....might have to, now. I was having good success with cutting the 3/4" EMT with a bandsaw instead of the pipe cutter and then pounding it onto the ends of the PVC. A little clumsy, and more work than I'd like, but effective. I found that it's easiest to flatten and drill the ends AFTER pounding the metal onto the plastic. It's amazing how much lighter the struts are....now I have to come up with something to do with them. (May or may not replace the Snowman's top dome- having it all metal is good in case I have to climb up there to adjust the beacon.) Might mount it on my bike.....

[mamagrrl]

Billboard covers.
Anyone got the skinny on how to seam this stuff without a
needle and thread?

Here's the skinny from a good friend who made her own dome cover from the billboards:
For the heat sealing surface, use a 4x4 about a foot longer than the longest dome strut. Sand the sealing side smooth, then cover it with scrim or other heavy-duty non-synthetic cloth.

For aligning pins, put a 16-penny nail in the center of the 4x4 about 3 inches from one end of the sealing side, and another nail near the other end, using the distance between the bolt centers of the long strut (or whatever aligning marks you're using) as the measurement, and leaving the nails sticking up about 2 inches. Grind the heads off the nails.

Place the 4x4 on a sturdy surface with plenty of workspace around it. Cover the heat seal surface with heavy-duty aluminum foil (I folded my foil lengthwise and used each side, taking care when I removed the foil so I could re-use it).

Put the edge of the first gore on the aligning pins, then overlap the corresponding edge of the second gore onto the aligning pins. Insure there is enough overlap (I used the full 3 1/2 inch width of the 4x4), and cover the top of the heat seal area with more foil.

The heat seal is accomplished using temperature, pressure, and dwell time. All three elements must be used. Experiment with scraps of vinyl until you learn which combination works best for you.

I used an old clothes iron, on its highest setting, and measured my dwell time (40 seconds) with a sweep-second-hand clock. I kept a firm downward pressure while sealing, taking care not to move the iron as it was sealing.

Allow the seam to cool to the touch, then remove the aluminum foil.

You will be able to tell if you're getting a good seal: no bubbles or scorch marks, the cooled seal will resist lateral separation.

[kampkalamazoo]

Great! That's the first good, detailed advice that I've heard regarding playing with billboard material!

[falk]

I'm sorry, what is billboard cover? Why is it desirable for a dome?

[falk]

Hi all; just a quick pointer to something you might find useful: http://geodome.sourceforge.net

The screen shots pretty much say it all.

Written for Linux, might be portable to windows.

[mamagrrl]

I'm sorry, what is billboard cover? Why is it desirable for a dome?

Billboards are no longer (generally) painted and re-painted with their ads. Nowadays, co's use big (BIG) sheets of vinyl, print the image on the vinyl and simply wrap the billboard with the vinyl.

The ad campaign ends and the billboard company has huge sheets of vinyl left on their hands. They must pay a dumpster to haul it away. We call at the appropriate time and for an agreement to not 'show' the vinyl ad ('cause if we embarrass their client, they'll both lose business and (more vitally) will stop giving the old vinyls away), we can have it if we haul it away. BUT, if lots and lots of people go in clamoring for old vinyls, it might piss 'em off. So, if you've got a buddy going in already, maybe batch up together and have the buddy get two, instead of one.

It's probably not the ultimate dome covering, but for many of us, it's the most economical as well as being hecka sturdy.

They are heavy. I can't lift a 60' x 120' vinyl by myself. Drag it, sure. Lift it, no way! Bring a truck. (yes, there are smaller vinyls.)

[falk]

Awesome, thanks for the info.

[robotland]

PROJECT SUPERSLIDE UPDATE
Any more obsessive and I'll be lashing myself to the hull....The NEW, IMPROVED plan is to construct a lighter but more reinforced slide-and-stairs combo from 1x4" and 3/8" ply. The one that's in place now is functional but heavy, and the something-like-a-rope-ladder over the top to walk up the slide on is stable but would scare those unused to it. Sort of hoped that walking right up the aluminum-clad surface would be possible, but you'd have to be part gecko- It's almost a 45 degree slope!I'm returning to an earlier idea, of having the slide surface flip up and over to reveal steps. More carpentry, but it could end up being almost half the weight and even stronger than before while possibly gaining a foot or two. (Current model's twelve feet long.)
I did look longingly at a spiffy plastic slide at Menard's yesterday....but couldn't pay 150 bucks. Not that I haven't blown that much in "R&D" TWICE already....
The only thing distracting me is the possibility of making it a ROLLER LUGE instead.....(*slapping self*)

[falk]

Hi all; looking into covering my dome with nice canvas. A number of tent makers sell canvas for a lot of $$$, but perhaps someone knows where the tent makers get their canvas in the first place?

[Nightterror]

Hi all; looking into covering my dome with nice canvas. A number of tent makers sell canvas for a lot of $$$, but perhaps someone knows where the tent makers get their canvas in the first place?

We bought ours at The Mill End Store in Portland. We spoke to a floor manager and she gave us 50% off mill price for colors they hadn't moved in awhile. Covered our 10 x 10 conduit structure in Turquoise, Orange and Blue for under $100.

[robotland]

Also look under AWNING AND CANOPY MANUFACTURERS.

[mamagrrl]

PROJECT SUPERSLIDE UPDATE
Any more obsessive and I'll be lashing myself to the hull....(massive snip)
I did look longingly at a spiffy plastic slide at Menard's yesterday....but couldn't pay 150 bucks. Not that I haven't blown that much in "R&D" TWICE already....

Saw this today and thought of you:
http://www.craigslist.org/eby/zip/74155125.html
Yep. Swimming pool slide. Free. But not near Kalamazoo.

Hope the slide is coming along well? Make it STURDY!!! I'm gonna want to slide on it!

[robotland]

[quote="mamagrrl
Saw this today and thought of you:
http://www.craigslist.org/eby/zip/74155125.html
Yep. Swimming pool slide. Free. But not near Kalamazoo.

Hope the slide is coming along well? Make it STURDY!!! I'm gonna want to slide on it![/quote]

SUPERSLIDE MARK V (or is it VI already?) UPDATE:
It's sturdy! Thanks for thinking of me...I though at first that that slide was fastened to the RV!
I built and installed the new version yesterday- It's basically a 14' long, one foot wide wooden stairway at more than a 45 degree angle. There's a little cart/platform that slides on top of the stairs at near-disastrous speed. All spiffy silver-painted, and soon it'll have hazard tape, a few lights, and a handrail. All that remains now is to decorate the cart and decide if I'm going to increase the friction and therefore slow the descent, or extend the bottom so you go skidding off across the playa when you hit ground level.....Guess which way I'm leaning.....

[upriver]

I placed an ad on my local freecycle list for emt conduit and had a few pieces in less than an hour. In the same amount of time someone else sent me an e-mail to check at the local metal recyclers/scrapyard. I found about 75 20 foot long thick walled 3/4" emt pipes for 25 cents per pound--which worked out to about to about 6$ each or just over half of Home Depot's price.

Looks like I'm building a dome.

Of course I didn't buy all 75, but I did buy 10 (200 linear feet) and I imagine I'll go back for another 10.

Just thought I'd put the idea of looking at scrapyards out there as a cheap alternative to the big corporate wharehouses.

Thanks everyone for all the good tips.

[robotland]

So.....you're going to use THICKWALL conduit? Can't beat the price, I guess....but THINWALL 3/4" is ideal for much domebuilding, and costs what you paid for the thickwall. That's gonna be a heavy one!