On 10/14/2014 2:09 PM, Donald Chester wrote:
Steve K7LXC wrote:
>I'm not an engineer but I can't find any validity in this
statement. Bigger towers use the pier-and-pin technique because it minimizes
leg
stresses on big towers with microwave dishes which are kind of a non-issue
Originally, tower manufacturers sold "dirt bases" and had instructions
for planting a tower section directly in concrete. The base tower
section extended all the way through the concrete so it could drain
properly.
I've not heard of these failing as the towers are designed to support a
specif wind and weight load.
Yes the pier pin base is better if properly installed. It's actually
more difficult to properly guy a tower set directly in concrete, but not
THAT much more difficult.
If not overloaded (a common ham practice) the tower should survive just
fine set directly in concrete. It's just that a properly installed pier
pin base subjects the tower to less torsional forces,
for your typical amateur installation. There are tens of thousands of guyed
towers with the bottom section buried in concrete and the incidence of that
failure mode is non-existent in my experience.
I've seen a number of tower bases fail, but not because they were set in
concrete. It was because they had poor drainage, did not go all the way
through the concrete causing water to collect in the legs and freeze.
"spider webs in the legs", or a base that let water collect on the
concrete around the legs causing the legs to rust through where they
entered the concrete.
73
Roger (K8RI)
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|