Bob wrote:Anything less than 3/4 will be crushed like a bug in the wind out there, and 3/4 is borderline for anything bigger than what you're building.
PocoJoe wrote:In reading about domes, people say over and over "stick your feet at the junctions, not in the middle of the pipe". I went online to find out what I could regarding the structural properties of EMT conduit, and found an online reference regarding buckling characteristics.
http://www.kineticsnoise.com/seismicboo ... 20data.pdf
The design recs here seem to suppoprt other people's experience- assuming Force Class II (251-500 lbs) the maximum span for 1/2" conduit is 3.14 feet, for 3/4" is 5.13' and for 1" is 11.75'.
Class III loads (501-1000, this would be somebody not sitting quietly but climbing actively) has span limit for the emt of 2.22" for 1/2"; 3.63" for 3/4", and 5.88' for 1".
This sure fits with Bob and CapJBadger's recommendations.
So--- Next question- since people tend to climb on the horizontal elements, has anyone made EMT domes that use 1" for the horizontals and 1/2" for the verticals? would sure save a lot of weight and money!
capjbadger wrote:Hmm... From my experience with 3/4" EMT, a 5' span will buckle at about 250lbs (in the middle). 500lbs seems rather high.
I've never seen anyone mix EMT dia. in a dome. The problem with your theory is when climbing, you press against those "vertical" struts to climb. If you make them thinner, they will get bent.
some seeing eye wrote: What's the difference in price - $150? 130#? 130# is a person and a half water supply. Whatever. But consider, when you go to sell your dome, after a few years of BM, who is going to buy or even want free a janky mixed tubing dome?
Dome frames are easy it's the cover that's hard, unless you use a parachute.
some seeing eye wrote:Desert Domes is also a great resource! They make dome frames showing you the value of the labor for making your own.
For a 24' diameter 5/8 3V the lengths line up with 10' pipe lengths, vertex to vertex - the OP has that down. That's ~83 lengths of 10' pipe and some spares. Home Depot online $180 1/2", $359 3/4". About 2x difference. Save costs by ordering as a contractor at an electrical supplier.
EMT weights 30 and 46# per 100 ft for 1/2 and 3/4. So 260# and 399# total assuming the tubes extend 1.5" beyond the vertex. OP calcs are similar.
Builders can do what they like, but I am going to be more inspired on the playa by an innovative cover and even more so by great creative people. than mixed pipe.
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