[Towertalk] 'Toes' of a tower concrete base

[David Jordan]

Gary,

Just installed my HDBX 48 in Virginia Northern Neck sand...made it easy for
the back hoe man...6'X6'X6'...fills up nicely with 7 cu ft of 3000psi
concrete.  Ensure you follow the rebar layout.  IF so, you'll have a very
nice foundation for that little tower.   We used the back hoe to support the
bottom section of tower already attached to the concrete legs. Keept it all
vertical while the concrete was poured. If you want pics email direct.

73s,
dave
wa3gin

ac7nj@bentonrea.com wrote:

> Gary/K3GB
> The design of the tower "toes" was carefully engineered by the tower
> manufacture and shouldn't be arbitrarily changed. Structural changes
> need to be made by a engineer or otherwise qualified individual.
>
> Randy
> AC7NJ
>
> -----Original Message-----
> From: towertalk-admin@contesting.com
> [mailto:towertalk-admin@contesting.com] On Behalf Of
> blueis@sprintmail.com
> Sent: Friday, June 28, 2002 4:33 AM
> To: Towertalk@contesting.com
> Subject: [Towertalk] 'Toes' of a tower concrete base
>
> In preparing for the installation of my Rohn HDBX-48 tower I noticed
> that
> the concrete base diagram showed what I refer to as a 'toe'.  That is,
> the
> hole for the base is rectangular -- something like 5' x 5' x5'.
> However,
> the bottom 12" flared outward creating an "L-shape" when viewed
> cross-sectionally --  similar to   _| |_  .  Being quick to draw
> conclusions, I figured the 'toe section' called for in the diagram
> provided
> additional leverage or strength.  I compared this effect to that of
> toggle
> bolts (AKA 'hollow wall anchors').  Once pushed through the small hole,
> the
> 'wings' spread out and provide strength against tipping or leaning.
>
> Now that plans have changed to use two AN Wireless towers I've been
> asking
> lots of questions about installation.  I have been told that you can
> eliminate this "L-shaped" area by simply making the hole rectangular.
> (The
> dimensions, of course, would have to be increased in order to make the
> vertical sides match what would have been the very outside edge of the
> 'toe'.)  The reason for the 'toe section', I was told, is NOT mechanical
> advantage or anything like that.  It was to save on concrete costs.
> Less
> concrete means less cost.
>
> My question:  Is this 'L-shape' essential to tower strength?  If I
> increase
> the horizontal dimension of the hole (to span the distance from left toe
> edge to right toe edge), do I weaken the structure?  Of course, this
> change
> WILL increase the mass of the concrete used in the base.  It would be
> easier, though, to dig the hole if all I need is a simple rectangular
> volume.
>
> gary b
> k3gb
> RVN BTO
>
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