On Wed, 18 Jun 2014 14:05:52 -0400, Jim Wilkins wrote:

"Tim Wescott" wrote in message
...

Come to think of it, the tension on the tube walls at the base of the
11'
section is something over 100,000 psi. Even if it didn't buckle on the
compression side, it'd bend right over.

Tim Wescott

Where did you locate the neutral plane?
-jsw

I figured that for a quick calculation that was going to say "it'll break
anyway", I'd rearrange the walls of the pipe so that they're 8" long, 4"
apart. =

1/4" thick walls gave me (1/4")(8") = 2 sq in.

That's going to result in an overestimate of the strength of the pipe --
but if the stronger pretend thing breaks, then surely the real, weaker,
thing will break.

I put the neutral plane half way between the walls, so the force from the
moment is

(33,000 ft-lb) / ((2")/(12 in/ft)) = 198,000 lb

Dividing this by the area gave me 99,000 psi, which is close enough to
100,000 given all the wild approximations.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com