[TowerTalk] hdbx rating

Doug Renwick ve5ra at sasktel.net
Mon Mar 13 09:40:56 EST 2006

Dejavu.  Time again to pull out some facts.
In my Rohn catalog I can not find any guidelines for guying.
However, the Canadian equivalent tower manufacturer
Taco/Delhi, does recommend guying their self supporting
towers.  One example shows a guyed 147 foot tall tower
package.  These towers were designed to be either self
supporting or guyed.  

Rohn boom length limits - To quote from the Rohn catalog
'Antenna types should be limited to those having a maximum
boom length of 10 feet.  No engineering data relating to the
use of boom lengths in excess of 10 feet is available and
the use of such boom lengths is not recommended.'  It may be
a liability issue or just that Rohn did not do the
calculations as implied above.  I believe that experience
trumps theory every time, and that increasing the wind
loading and torque on these towers with guying changes the
risk factor very little IMO.  I suggest that until you have
seen my Delhi tower farm, you would never know how strong
these towers really are.


Subject: [TowerTalk] hdbx rating
The HBX/HDBX towers were designed as self supporting towers,
not guyed.  And, liability issues forced them to restrict
boom length to 10'.  Will they hold more than rated?
For a long time?  Undoubtedly.  Are they OK guyed?
but not by design.  Can you get a building permit for one,
if you
plan to exceed the design specs?  Only if you fail to
disclose some details.

If you put it where it won't hit a house, then it probably
matter, unless your local code officials say it does.  And
a different problem, entirely.

As for stories about how big and how much, and who else did
they simply don't matter.  Rohn under-specified their towers
liability reasons, for a long time.  You can get away with
quite a lot,
although you bear risk when you do.

The idea of using a torque tube and base mounted rotor is a
good one,
if you can finesse the zoning folks. And as a final
a bitch to climb, having no horizontal bracing elements.
Don't forget
that the foundation will cost as much or more than the tower

jimjarvis at ieee.org
jimjarvis at verizon.net

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