On Mon, 24 Mar 2014 20:18:02 +0000, Joe Farmer
wrote:

replying to etpm , Joe Farmer wrote:
etpm wrote:

On Sun, 23 Mar 2014 16:19:03 +0000, Joe Farmer
Greetings Joe,
It depends on which way the 2 x 6 tubing is loaded. If the tubing is
loaded on the 2 inch wide direction it will be 27 times stiffer that
putting the load across the 6 inch dimension. Which way are you going
to use and how much deflection can you tolerate?
Eric
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I'm loading it on the 2" side . The number of arches can be decided when I
find out how much one will support. The building is an arch building 60' x
150' long. The arches are in a 60' span.

Why not add half a dozen more arced tubes (such as used on the inside
but 1 to 2' longer) on the outside for the conveyor system, Joe?
Attach to the end supports on the building for stability and you're
set. The (what, 1.5 or 2"?) tubing can easily handle the 200lbs per
ten feet of conveyor and it leaves the roof intact. It would probably
be less expensive in the long run, too, plus it leaves your existing
building untouched, except for the tie-ins at the 4 top "corners".

--
The most decisive actions of our life - I mean those that are most
likely to decide the whole course of our future - are, more often
than not, unconsidered.
-- Andre Gide