I have mounted several towers in this fashion. I used some 40" face tower
(two 20' sections mounted in cement) with about 35' sticking up, then
fabricated a base to match the Delhi/Rohn HBX series and then mounted a 56
footer. There is no engineering involved with whatever freestanding tower
you put on top - it is designed to freestand at ground level or 50 feet
above it. In real world, the extra wind exposure might reduce the safety
margin a bit.
The base certainly deserves some engineering. Mine got none. I had some of
this 40" face tower - very strong with 4" x 4" x 3/8 wall 120 degree angle
legs - and I arbitrarily decided it was strong enough. Then and still, I
worry more about the Delhi surviving rather than the base. However they
aren't overloaded - my two situations involved a 56 Delhi with a 7 el 6m
yagi (22 foot boom), the other a 48' Delhi with a TH6. While the 48 footer
is on the ground for another reason, the 56 footer has survived just fine
and is just as wobbly to climb as any other 56 footer that is ground
mounted. The 40" face tower was chosen because it was on hand and matched
the size of the base section of the Trylon tower I had - and which may
eventually wind up on top of it.
I don't know the base size and capability of the aluminum tower you
mention - but aluminum towers have always seemed pretty expensive to me,
compared to the windload you get for those $$. I'd look at 96 feet of
Trylon first and mount that on 60 feet ( cemented 6-8 feet in the type of
ground I'm used to) of 48" or 60" face broadcast tower.
73 Don
VE6JY
----- Original Message -----
From: "Douglas B Rupp" <rupp@gnat.com>
To: "Robert Shauger" <rgshauger@myyellowstone.net>; <kk9a@arrl.net>;
<TOWERTALK@contesting.com>
Sent: Monday, June 23, 2003 02:05
Subject: Re: [TowerTalk] Combo guyed base, free standing tower
>
>
> > Agreed. A 100' foot aluminum tower properly installed has a minimal
> > windloading capability in the first place. That is really the bottom
> line.
>
> That's fine. I only need minimal windloading,
>
>
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