[TowerTalk] A near imminent TX-455 failure

[D. Scott MacKenzie]

>From the photographs, it appears that failure originated from the edge of
the weld beads. Usually this indicates lack of fusion on the weldments.
Failure should occur in the base metal.  It also appears that the tower is
either painted or galvanized (I can't tell because I can't see well enough
at the fracture.  Since the welds appear to have failed at the weld bead,
grinding the weld bead off, then rewelding would be appropriate.  I would
also suggest some sort of backing plate to reduce the loads on the weld may
be utilized to reduce the stresses on the weldment.  The hard part will be
getting the  joints lined up for welding.

In my former life doing failure analysis on structures and components,
unfortunately, this is a common mode of failure, most often associated with
inadequate penetration of the weld.

IMHO

Scott aka KBOFHP


-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com]On Behalf Of Nick - VE3EY
Sent: Sunday, November 13, 2005 8:26 PM
To: towertalk at contesting.com
Subject: [TowerTalk] A near iminent TX-455 failure


I am posting this note on behalf of a friend of mine.

His 55 foot TX-455 US Tower is on the verge of collapsing down.  The
owner just noticed that two out of three legs of his tower just broke
down.   The legs snapped just above the mounting ears where the tower is
fastened to the "T" mounting plate.   We suspect that some 90 km/h wind
gusts we have had here in Toronto last week may have been a contributing
factor.

The tower is currently nested and the antennas are still on top of it.
It is basically holding on only one of the remaining legs and a few
cross braces.   It was installed brand new in 1990 and it had a 2 el GEM
Qubical Quad installed ever since.   In 2003, owner replaced the short
mast with a 22" cromoly nested about 3" inside the tower and added a
home made rotary dipole for 30/40 m at about 10 feet above the Gem
Quad.   The dipole is a modified Cushcraft D3W warc dipole.

The pictures of the damage can be seen here.   http://dx.fireroute.com/TX455

We are looking for some advice how to remedy this problem.   Would there
be any way to fix this tower short of buying a new one?


73,  Nick
ve3ey


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