[TowerTalk] New tower

[W7CE]

>
> I just looked on line and I see no reference to that. On 45G they show and 
> talk about the gravel in the bottom of the hole, tower legs placed on the 
> gravel so they drain, etc etc. But then, maybe I'm looking at the wrong 
> page......... OR maybe pier pin for really tall towers. My 40', 45G, is 
> "in the ground". Now if I was lucky/brave enough for 80' or more, I would 
> probably go pier pin. As always, YMMV.
>

As far as I can tell, all of the bases that show the legs placed on gravel 
are for free-standing and bracketed towers.  The guyed towers all specify 
bases CB1 to CB3 which are all pier-pin bases.

Over the years most ham installations have ignored Rohn's instructions and 
buried the base in concrete.  Commercial installations, which certainly 
required an engineer's stamp, have primarily used pier-pins.  There's a 
reason.  The pier-pin bases are less likely to fail due to twisting and 
bending at the base.  K7NV has done a study of this and posted the results. 
It makes interesting reading.

http://k7nv.com/notebook/towerstudy/towerstudy1.html

You'll note that the tower that failed in this study did so at the base 
section buried in concrete, not the upper sections.  When the base was 
replaced with a base that can move (i.e., a pier pin), the tower survived 
with much large safety margins.