On 8/20/22 4:08 PM, Dave KØEKL wrote:
To ease maintenance I want to relocate my rotator to the bottom of my tower.
The existing mast is 2" diameter ¼" wall 6061-T6 aluminum tubing. The rotor is
8 feet below the top of the tower / thrust bearing.
What is the best way to join additional lengths of tubing together to reach the bottom? I'm thing
about buying tubing that is 2" ID, cutting it into 18" or 24" sections, slitting it
and slipping it over the 2" OD sections to be joined and clamping with SS U-bolt clamps like
those sold by DX engineering. Will this provide enough coupling friction between sections to
prevent slippage?
Much better to just get something that fits snugly inside, and run bolts
through. The load isn't huge, so you don't need fancy bolts (the bolt is
carrying the torque, and the weight, in shear)
Have you considered using steel pipe with standard couplings (and a jam
nut).
How tall is the tower?
From a torsional stiffness standpoint, large diameter, thin wall, is
better. I've not run the numbers, but something like 3" or 4" diameter
irrigation tubing (or steel EMT) might not be bad. And there's off the
shelf couplings for it. Probably something with a through pin would be
better, though, than something that clamps. Clamps inevitably loosen,
unless their ungalvanized steel, and they rust into place (like muffler
clamps). Of course, removing them then requires a saw or hot wrench.
Also, can I get away with using 1/8" in wall 2" OD tubing from the existing mast to the
base of the tower or should I use ¼" wall all the way to the bottom.
Since tubing is basically priced by the pound, 4" tubing 1/8" wall is
better than 2" tubing 1/4" wall - they cost about the same (same cross
sectional area), and the 4" tubing is MUCH stiffer and stronger in a
bending load sense.
Big and thin wall is almost always better than small and thick wall,
except if you're holding pressure, or there's forces causing denting.
Thanks.
-Dave K0EKL
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