[Towertalk] 'Toes' of a tower concrete base

[Mike Wetzel]

Just can't hold my tongue any longer.

You guys with all the concrete and money!

Up until 2000, I had up 4 towers over 100' (Rohn 45 and 25) and only 1 had
any concrete at all (in 2000 for my Rohn 55G tower for my 80 meter beam
several local ganged up on me and made me pour concrete).  I stayed away
from using concrete because of the cost.  One tower used an old Rohn AX
screw anchor base, 2 use 6" x 6" wood planks/blocks (similar to using a pier
pin) (not self supporting) and I used temporary guys.  For anchors I use a
combination of power driven screw anchors and hand anchors.  Early on I used
salvaged guy wire pieces (alum-a weld) from the utility since I broke up the
guy wires anyway bought at scrap prices.

I am an engineer (not structural or mechanical) and I did have good help
that steered me using common sense (that seems to be evaporating today).
Early on I did have some failures (booms bent, tornado took down a tower,
etc) but that is part of it, I figured.

One other thing, I used aluminum for masts (engineered) and water pipe (no
stacking) not expensive Chrome Molly.

I'm glad I'm not starting out now in the hobby today trying to put a station
together, because Mr. Safety, Mr. Lawyer and Mr. Manufacturer would suck my
wallet dry if I followed all their stipulations to a 'T'!

Mike W9RE

> -----Original Message-----
> From: towertalk-admin@contesting.com
> [mailto:towertalk-admin@contesting.com]On Behalf Of David Jordan
> Sent: Friday, June 28, 2002 10:16 AM
> To: kr7x@attbi.com
> Cc: blueis@sprintmail.com; Towertalk@contesting.com
> Subject: Re: [Towertalk] 'Toes' of a tower concrete base
>
>
> My guess is sales of towers were dropping as the cost of concrete
> went up...at
> todays cost the concrete and digging the hole cost more than the
> tower!  Then ad
> the cost of a climbing belt and gin pole and the little 50ft self
> supporting
> tower becomes a couple thousand dollar project.
>
> Enjoy,
> dave
> wa3gin
>
> kr7x@attbi.com wrote:
>
> > Gary:
> >
> > IF you make the foundation straight sided at the plan
> > base dimension (largest size at bottom) you should have
> > no problems as far as your installation is concerned.
> >
> > I also wondered why they called out a truncated pyramid
> > shape for a foundation in soil. It is very hard to shape
> > without forming and does very little to increase the
> > capacity for the extra effort. (my opinion only)
> >
> > 73
> > Hank Lonberg, S.E.,P.E.
> > KR7X
> > > 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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