The cross won't hold a self supporting upright reliably in all soils,
and it might be marginal on supporting the downward force on a guyed tower.
Supporting downward force requires sufficient 'footprint' of the base.
The combined weight of a heavy concrete base and the tower and
equipment, multiplied by the radius of the base, prevents the wind from
tilting the base and tower without depending on sideways soil
resistance. One has to measure soil characteristics to design a base
that depends on soil resistance, and the cost of that is greater than
the cost of a concrete base for typical amateur towers. Another factor
in making them simple is the fact they are below ground and are
basically 'floating' in the ground, so it is usually not necessary to
assess the load bearing characteristics of the soil. Watch out for the
More sophisticated and larger structures require soil measurements and
Utility poles are relatively small and an occasional 'leaner' isn't a
big problem. It can be tolerated or repaired.
Similarly, one can compromise on temporary antenna supports, if the
investment is small.
Hope this helps.
73 de WO?W
PS: What is your QTH? My wife's grandfather was from Wexford and she
has relatives in Dun Laoghaire. We flew our Cessna to Ireland in 1987,
with an IC-735 for HF communication and enjoyed the trip and the visit
Tim Makins, EI8IC wrote:
>Many years ago, at school, I remember seeing the illustration of how you
>could move the world if you had a long enough lever. It occured to me
>recently that the same idea could be used to construct self-supporting tower
>bases, but, as I'm not an engineer, I thought I'd come to Towertalk to be
>The idea is: Instead of the usual cube of concrete, how about using a
>horizontal cross. Maybe 2 feet deep, and 2-3 feet wide, with an internal
>rebar cage to prevent snapping. The length of each arm of the cross to be
>determined by whatever formulas you guys use - I was thinking along the 12
>foot mark, as a discussion-opener.
>You will note that I haven't mentioned tower height, as obviously all the
>parameters inter-relate. If you must have a figure, lets say 40-60 feet.
>The reason for this ? Well, I was thinking 'outback', and 'developing world'
>here, where a mechanical digger isn't always available. Easier to dig slit
>trenches than a big pit. Less problems from cave-in too.
>Sit down, take one of these beers, and discuss.
>73s, Tim EI8IC
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
>questions and ask for Sherman, W2FLA.
>TowerTalk mailing list