[TowerTalk] Non-Guyed Support for 80m Horizontal Loop at 35 feet

[jimlux]

> Now the question is what is needed for steel poles to handle the loads
> without buckling?  This is an interesting question not addressed in any
> antenna books I have seen maybe because of the liability issues.  There
> are certainly a number of hams that don't have nature provided antenna
> supports or they are in the wrong place.  Also, a self supporting pole
> might work where aesthetics or CCR's are a concern.  I priced flagpoles
> and they are expensive, much more than $1000 for a 35' delivered on a truck.
>

That's because buckling loads for tapered tubes are tricky to calculate.

For a straight pipe, though, it's pretty easy to determine failure load 
for a bending load.  By the way, buckling refers to failure when the 
member is loaded in compression.

If you know thickness of the wall and the diameter, you can figure out 
the compressive/tension load for a given load.

Bending moment for failure = (yield strength)*(second moment)/(Douter/2)

second momemt = pi/64 *(Douter^4 - Dinner^4)

Douter = OD of tube, Dinner = ID of tube.