On 1/27/18 10:08 AM, Wilson Lamb wrote:
WOW, what an appealing idea! It's fun to be on here and see such things pop up!
Imagine an antenna dragging at 200 lb, 100' up, and you have 20K ft lb at the
base.
so you need 1000 lbs at the end of the upwind leg. Most any earth
anchor will do that.
Then add for tower, a few times that, and you get an idea of the overturning
moment range.
Then it occurs to you, if you are a true ham scrounger, that frames from old
house trailers are available as junk, if you are in the right place at the
right time, and there are some nice beams!
I think the tricky part is taking the bending load of the beam you have to cut
across the joint.
Perhaps a good welder could make the joint by cutting both beams. Then I'd put
tension gussets across the cuts. Those beams are narrow, but long, so you
could easily double them to resist buckling and add bending strength!
Any sort of box truss (whether triangular like Rohn sections, or square
like rigging truss) can easily handle this if it's reasonably large (2
ft across, say)
The challenge is in "workmanship" (don't want a weld failing) and
inadvertent stress concentrations (gussets in the wrong places can make
the load higher in a concentrated place)
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