[TowerTalk] concrete bases for freestanding towers

[Grant Saviers]

Bases have gotten bigger.  Crankup mounting plates have much heavier 
steel and angles rather than plates.  The catalogs show much less 
concrete than the actual wet stamped drawings I have for my HDX589 UST 
freestanding.  An owner of an earlier 589 told me his base is much 
lighter, but I haven't had a chance to measure it.  The lattice pitch on 
the 589 also varies, more strength where they overlap.  I'm not sure 
this was always so, the Tri-Ex 354 I have is constant pitch of  bracing.

Why? One significant reason is the "upsizing" of the wind speed 
specifications as standards were revised.  Other reasons could be better 
structural analysis which no longer needs a Cray supercomputer, or 
liability/insurance concerns.

Grant KZ1W

On 5/13/2011 5:18 AM, WA8JXM wrote:
> Many years ago I had a 64' freestanding tower with a 3el triband beam (TA-33) on it.  The base was only 2 cu yards of concrete.  As far as I remember, that was all the manufacturer (Heights) recommended at the time.
>
> Now when I look at anyone's recommendations, the base requirements are much larger.  Rohn (and others) recommends 3 cu yards even for a 40' BX tower.    I had used only 1 cu yard for a freestanding 40' tower.
>
> Is my memory faulty, or have the recommended bases grown over the years?  Were the old recommendations inadequate, or has everyone grown super conservative over the years?   "If one yard is adequate, three will be better, so let's use five yards"???
>
> As one ham commented on the air yesterday, the only failures he has ever heard of were in the tower itself, not the base falling over.
>
> Ken
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