[TowerTalk] I Beam Base

jimlux jimlux at earthlink.net
Sat Jan 27 13:58:07 EST 2018

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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