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"Then I plugged all these numbers into their appropriate place on a round tubing beam deflection calculator" Could you show us this calculator? Maybe this is where something is going wrong.

Jon got it right-
It appears you're are trying to determine the deflection of a 36" long tube simply due to its own weight. From a practical standpoint can you envision a 36" long tube deflecting almost a 1/2" due to its weight? I'm having trouble visualizing that.

Why work in two unit systems? Stay in one system.

The acceleration of gravity has nothing to do with a beam deflection problem.

Hang in there. That's the purpose of this forum, to try out ideas and to get feedback.

Cheers,
Roy

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Build log http://www.locostusa.com/forums/viewtopic.php?t=16510

Yes, for sure, hang in there. It is important to expose your thinking and methods. Otherwise, there's just no way to see where things are going wrong.

I'd definitely second staying with the systems of units that are native to you. All the conversions are sure to cause trouble.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

ok, now I see the errors in my ways, lets try compression then. I am just using the scenario I created to learn more about deflection and stress from what ive been reading in books. Lets assume the ends of the tubes are fixed, with no vertical loads but with horizontal loads only from both ends.

If I read your description correctly this is what you are proposing (see sketch). If yes, I believe you've now thrown yourself into a "buckling" problem which of course can be analyzed.

As the loads on each end increase the thin wall tubes will deflect and buckle in the center.

Give it a try and see what happens.

Roy

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Build log http://www.locostusa.com/forums/viewtopic.php?t=16510

ok, I think I can do this