How to build an EMT conduit sphere?

Ideas, advice, tips, and tricks regarding shelter, shade, tents, and camping. Yes, this includes RV's too.

How to build an EMT conduit sphere?

Postby heikediguoren » Wed Nov 13, 2013 3:24 pm

For 2014 I would like to build a geodesic sphere--I was thinking a buckyball would be nice--as I am sure there will be nothing risky about having a giant football-shaped object lying around in an area known for high winds. Regarding that, of course it will be held in place with ground screws and guy wires, or suspended from something, or mounted on a vertical axis--still in early planning stages, but yes I'm aware of the need to restrict its cross-playa wandering. Moving on.

There are many wonderful websites with calculators and instructions for building domes out of conduit, but not really anything about making a whole sphere. I imagine I can cobble something together by researching the geometry of a truncated icosahedron and working out all the bend angles, and trial-and-error my way through the construction process, but I thought I'd better find out if someone else has already figured this out. Any ideas?
User avatar
heikediguoren
 
Posts: 26
Joined: Thu Jul 19, 2007 6:09 pm

Re: How to build an EMT conduit sphere?

Postby theCryptofishist » Wed Nov 13, 2013 3:25 pm

Make two domes. Tie them together.
Simon's real sig line?

Embrace the Sock

Winners never quilt, quilters never win...
User avatar
theCryptofishist
 
Posts: 37437
Joined: Mon Feb 23, 2004 10:28 am
Location: In Exile
Burning Since: 2017

Re: How to build an EMT conduit sphere?

Postby heikediguoren » Wed Nov 13, 2013 3:54 pm

Yes, that would be a pretty easy way to do it. a side benefit is that when we're halfway done, we have two complete domes to play with as opposed to one half-finished ball.

also, it turns out someone has in fact already done this very thing and made a site all about it: http://www.luxfamily.com/jimlux/robot/emtsphere.htm
User avatar
heikediguoren
 
Posts: 26
Joined: Thu Jul 19, 2007 6:09 pm

Re: How to build an EMT conduit sphere?

Postby GreyCoyote » Wed Nov 13, 2013 4:57 pm

The math gets a bit hairy, but as Fishy has said, you can essentially build two half domes and bolt them together. There are some caveats however, not the least of which is using only even-frequency domes so the domes are exactly a half sphere.

If you want to chat about this, PM me, especially if you are thinking about making a solid sphere (not just a lattice-frame). :mrgreen:

Edit: the guy who wrote that web site clearly has never worked with higher-frequency domes. You do NOT simply smash the ends with a hammer and eyeball the holes. His work, frankly, is complete crap ("adjust with a big pliers and sledge if the holes dont align..."). While this ethos may work (barely) for a 2V dome, thats as far as he will ever get. PM me, or we can do it in public if you wish. :mrgreen:
"Give me an underground laboratory, a half a dozen atom smashers, and a beautiful girl in a diaphanous veil waiting to be turned into a chimpanzee, and I care NOT who writes this nations laws"!
User avatar
GreyCoyote
 
Posts: 717
Joined: Mon Feb 18, 2013 9:24 am
Burning Since: 2000

Re: How to build an EMT conduit sphere?

Postby Lightnin' » Fri Nov 15, 2013 12:40 pm

You guys are overthinking this. Go to http://www.desertdomes.com/domecalc.html If you build an odd frequency dome, there are instructions to build it 3/8 or a sphere, or 5/8 of a sphere. If it is an even frequency dome, the instructions are for a half sphere.
Seems logical to build enough struts to do the whole sphere, and bolt it together. Build a 5/8 sphere, and just keep going when you get to the ground. Or likewise for a half sphere. You will have some doubled up struts if you just take the half sphere list and build two sets, likewise if you add the 5/8 list and the 3/8 list for an odd freq.
I built a 3 freq dome from this site and have used it for 6 years now. The beauty of the odd freq. is that the bottom section of struts is perfectly vertical, as the equator of the sphere is halfway up from the ground in that bottom section. This way you get more usable space inside. With an even freq. the equator is at ground level when you build it half sphere.
I have seen several on playa of the exact size as mine, as the longest strut is half of a full stick of conduit, INCLUDING the extra 1 1/2 inches you have to add to the 'hole to hole' dimensions given in the chart. I imagine however that you would want to build one quite a bit smaller if your going to build a full sphere. My radius is around 11 ft, 22 ft diameter, with ceiling height (5/8 sphere remember) at around 13 ft. Much to big to build full sphere, not to mention the idea of tying it to the ground........
User avatar
Lightnin'
 
Posts: 5
Joined: Fri Sep 11, 2009 2:38 pm
Location: Redding CA

Re: How to build an EMT conduit sphere?

Postby heikediguoren » Fri Nov 15, 2013 2:10 pm

So, a bit of planning and scheming later, I've decided to make a relatively small sphere, diameter 10 feet. Among other reasons, I'm planning to initially stage this piece in an art gallery, and that's about all the space that I have to work with.

The challenge is that I want people to be able to climb inside, and that means having struts just about 3' long, I think. A triangle with 2' long sides seems really snug. Which, using the desertdomes calculator (thanks Lightnin'), basically limits me to a 2-frequency. If people are going to climb all over this thing then they need to be able to hang off the struts, and as I understand it, the lower the frequency, the less weight each strut can bear; will 2-freq be stable if I've got, say, a couple of 200 lb people monkeying around on it, assuming I'm using 1" EMT conduit?
User avatar
heikediguoren
 
Posts: 26
Joined: Thu Jul 19, 2007 6:09 pm

Re: How to build an EMT conduit sphere?

Postby BAK3R » Thu Jan 16, 2014 6:36 pm

Build a 3/8 3V and a 5/8 3V 16' radius domes. This gives you approx 3' struts out of 1" EMT. Bolt them together for an 8/8 geodesic ball.
User avatar
BAK3R
 
Posts: 28
Joined: Tue Jan 03, 2012 4:38 pm
Location: Reno, Nevada
Burning Since: 2002
Camp Name: 6:30 & Desderata (AEZ)


Return to Shelter & Camping

Who is online

Users browsing this forum: No registered users and 3 guests