[TowerTalk] Heights aluminum tower

n4kg@juno.com n4kg@juno.com
Fri, 10 Dec 1999 17:17:52 -0600

The Heights Aluminum tower which failed with a KT34XA at 80 ft
failed due to one of the tapered legs folding in on the BOTTOM
or NEXT to BOTTOM section, which is pretty BIG.

It would seem obvious even to a non-engineer that adding a
horizontal brace to the top of each section would GREATLY
strengthen the tower.  ROHN has been doing this for decades
on their straight sections.  How many pennies could Heights 
be saving by taking the chintzy and weaker way out?

If they insist on the minimal cost saving, it would make a
LOT more sense to remove the horizontal brace from the
BOTTOM of the section where the legs are straight rather
than leaving a BENT INWARD leg supported in only ONE

Perhaps the failure was due to a material weakness in
one of the (unsupported) tapered legs.  Do YOU want
to take that gamble.  I bet if the leg had been braced,
I wouldn't be telling this story.

Another example of the astute engineering on the Heights
(and other?) aluminum towers is that they taper the BOTTOM
of the legs so that they fit INSIDE the top of the legs on the
next lower section, forming a perfect path for water to flow
down the leg and INTO the Leg Joints !  

When I dismantled my father's 40 ft Heights aluminum tower,
I resorted to a car jack to try and separate one of the sections.
It RIPPED the LEG  OFF below the joint!

Heights recommended (on TowerTalk) that users should
dismantle their towers every 5 years and reapply Penetrox(?)
or some other anti-oxident to prevent this from happening. 
How many users do you believe will follow this sage advice?
(Taping the leg joints should provide some protection).

Notice that ROHN tapers the TOP of the R25 legs and welds
a LARGER diameter piece to the bottom of the R45 tower
sections, forming a hood to protect the joint from water
intrusion.  Obvious.

I guess I'm being too "arbitrary".  :-)

de  Tom  N4KG

On Fri, 10 Dec 1999 16:01:46 +0000 K4SB <k4sb@mindspring.com> writes:
> I would tend to agree with Tony on this one. I've had a used
> heights up to 120' with a wide spaced heavy dute 20 monobander on
> it, and no problems at all.
> When I took it down, I put a rope from a high pine to the top of
> it, sawed off one of the legs, and let it just fold over. ( - the
> beam of course ) When it came to the horizontal position, it was
> a straight as an arrow.
> And it's now up as an 80 footer with a 402CD on it.
> I suspect the problem might have been the schedule of sections in
> use. You can't expect it to taper from the largest to the
> smallest sections and go on up. This tower has been around too
> many years for someone to arbitrarily question the design.
> 73
> Ed

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