USE WITH CAUTION: WHILE I BELIEVE THE BELOW METHOD TO BE ACCURATE I STRONGLY RECOMMEND THAT YOU REVIEW IT FOR YOURSELF BEFORE PURCHASING ANY NEW TUBING OR TAKING ANY FINAL ACTION; AND, I ENCOURAGE ANY OTHER FORUM MEMBERS TO COMMENT ON THEIR VIEWS OF THE CORRECTNESS OF THE BELOW SOLUTION I HAVE GIVEN.

If all other factors are kept equal then it appears that the deflection of your curved tubing is inversely proportional to the I (Moment of Inertia) of the X-section of the tubing you use; and, by using your existing tubing I and deflection and your desired acceptable deflection values, you should be able to determine the new minimum wall thickness for the tubing by the following:

The simplified equation for solving this is:

deflection2 = deflection1 * [ (D1^4 - d1^4) / (D2^4 - d2^4) ]

Where: deflection1 = your current curved beam deflection

deflection2 = your desired new curved beam deflection

D1 = your current tubing O.D. (10 in)

d1= your current tubing I.D. (9.80 in)

D2 = your new tubing O.D.

d2= your new tubing I.D.

This is going to be a trial and error solution by varying d2 to achieve your desired deflection2 (assuming your tubing O.D. will be same on the new tubing) My preferred method for solving this would be to use MS Excel and its “Goal Seeking” function.