- Thread starter Dave Hodges
- Start date

Not me, but I'll take the #460 square on the pool sheet......single strut without a jury strut.Anybody want to tell me how much force it will withstand?

I ran 1-3/16 OD, 0.058 wall, 85 long and with pivoting ends. It calcs out to 1349 pounds in compression from combined Euler and Johnson method as presented in Shigley.

Then I consulted the Summerill tables for 0.058 wall tubes, interpolated between the 1-1/8 and 1-1/4 which plays out at about 2500 pounds and 55-60 inches, so it does not provide much help.

Billski

Some fool left aluminum E in his spread sheet cell.Not me, but I'll take the #460 square on the pool sheet

Billski is obviously much better at the 'details'... and only 7 pounds more than my sheet.

I ran 1-3/16 OD, 0.058 wall, 85 long and with pivoting ends. It calcs out to 1349 pounds in compression from combined Euler and Johnson method as presented in Shigley.

Then I consulted the Summerill tables for 0.058 wall tubes, interpolated between the 1-1/8 and 1-1/4 which plays out at about 2500 pounds and 55-60 inches, so it does not provide much help.

Billski

This is a very slender column where the basic Euler formulation is applicable, so difference in yield strength won't matter much. Now the seam weld in EMT, that might have some influence...

Billski

Thanks.

Can you add a jury strut? if you can cut the unsupported length to around 50 inches you might reach your ~3k# load.

Thinner wall 1.5" or 2" diameter tube is lighter in compression. Cessna struts are 2", I think.

Terrific, the math works.

I am concerned that this light a tube will sag under airloads and its own weight enough to give you curved column effect. There is a reason the Summerill tables play out where they do. With a strut this slender, the jury strut recommendations are particularly appropriate. Think on that more...

Putting the rivet holes in can further destabilize the tube. Test is necessary...

Might be lighter to just go with an appropriate streamline steel tube than adding a streamline shape. They have a bunch of sizes here.

https://aedmotorsport.com/store/materials/4130-chrome-moly-streamline-tube-1

Billski

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I'll third the suggestion to use a larger diameter.

Interesting find. Oval tubing might be nice for some things. Bellanca tail feathers, for example are built using oval tubing. The large radius of these streamlined profiles probably reduces the chance of cracking - which was (maybe still is?) a problem with the standard profiles.T They have a bunch of sizes here.

https://aedmotorsport.com/store/materials/4130-chrome-moly-streamline-tube-1

Billski

Bruhn has "MAX" value of .8Fcy for tubes....(Fig 7.7)....could be less Bruhn 73 C7..... Fe is Euler????? .....I would use the Tubing charts Bruhn C4 or Summerhill tube charts.So this test validates the Fcr=0.877Fe formula.

https://www.homebuiltairplanes.com/forums/threads/4130-to-aluminum.26793/page-2#post-365546

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