I am designing a Gin Pole to lift a 500# load. The pole will be hollow Aluminum tube 24'x3"x3" and .125" wall thickness pinned at both ends. The pole will be at a 45 degree with the top secured with a horizontal 1/8" steel cable secured to a tree. Thus vertical load cable and the horizontal support cable to the tree will be at right angle putting a pure compression load on the pole of 700#. Will the Aluminum tube describe safely withstand such a compressive force in column without buckling ? If not is a a heavier wall thickness prescribed?

  • $\begingroup$ Are you sure of "pure" compression? the mounting will be perfectly centred so as to not cause any side load? $\endgroup$
    – Solar Mike
    Oct 17, 2022 at 18:16
  • $\begingroup$ Thanks Solar Mike $\endgroup$
    – David Nagy
    Oct 18, 2022 at 23:05

1 Answer 1


Euler buckling equation is{

$Pcr = \dfrac{\pi^2EI}{le^2}$

for 3x3x1/8 aluminimun tube,

$E = 10x10^6 psi, I = 1.78 in^4$

for a column with pinned ends, K = 1.0, conservatively use 1.2,

$Le = K*L = 1.2*24*12 = 346 in$

$Pcr = \dfrac{\pi^2*10^7*1.78}{346^2} = 1467 lbs > 500 lbs$

Yes, strengthwise it would work provided the end condiditions are as assumed, and there is only compressive stress on the pole. But instability caused by flexibility could cause problems.

  • $\begingroup$ Thanks, I couldn't get my diagram to display, and even with the 1.2 safety factor it's 2x the expected load. $\endgroup$
    – David Nagy
    Oct 18, 2022 at 23:18
  • $\begingroup$ 1.2 safety factor is for the potential defects in the material/tube. you shall watch out for incidental eccentricity which can introduce a bending moment. Otherwise, it will be fine under the load. $\endgroup$
    – r13
    Oct 19, 2022 at 14:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.