[TowerTalk] Rohn HDBX48 failure

[Doug Renwick]

Interesting.  I see that the specs. for a HDBX48 are a 18 sq. ft antenna max.
at point 3 ft above the apex of the tower for a 70.7 mph wind .
With a note: "antennas developing a large twisting moment due to wind must
not be used on this tower.  Antennas should be limited to those having
maximum boom length of 10 ft.  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."

I am surprised at the high (18) square footage they have calculated.  They
also appear conservative in their max. boom length mainly because they have
not done the calculations.  They are also saying that for this self supporting
tower that failure will likely be from a twisting moment.

Chuck.  The devil is in the details.  Please share with us the details of
your loss. Was your HDBX48 sensibly guyed?  Share how you had guyed the
tower.  Did the guys break or pull out first?  Was the tower guyed at the top
and also lower?  What was the wind speed?  Was it a hurricane or tornado?
How long a mast did you use?  How far above the apex of the tower was the
KT34XA mounted?  Did the mast collapse first?  Was the HDBX48 mechanically
sound?...i.e all cross braces in place and secured.

Doug/VA5DX

Chuck Sudds wrote:

> Yes Dave, *I* was one of those idiots who attempted using an HDBX48 tower 
> to hold up a KT34XA and a 14 element 2 meter beam atop that!! 
> Unfortunately, I can no longer find any of the photos of that disaster of 7 
> years ago, it is still etched firmly in my memory!  DON'T DO IT!  I was 
> lucky..... nobody was killed or injured!  And yes, I even had mine 
> guyed!!  I sure do sleep better with my 100ft Rohn 45G properly guyed these 
> days though.  Do what the manufacturer says!!
> 
> Chuck  KØTVD