The lower strength of welded aluminum is recognized in the Aluminum
Association Specifications standard, and the new Heights series used the
lower value in the design and analysis of the tower sections. That standard
makes no mention of 'baking' a weld to regain the lost strength.
Keep in mind that the 'allowable' strength of any material is the value used
in any design. It is arrived at by discounting, with a safety factor for the
material in question, the minimum specified limits of the yield & ultimate
stress for the various types of stress (tensile, shear, & bearing).
Generally the discounted yield strength is the value used for design
purposes. Thus the design has an inherent 'safety factor against failure,
the main purpose of which is to have some margin against imperfections in
the manufacturing process or other variables.
Of course, if the welding is defective, all bets are off.
I do know that Heights is using the TIG welding process in the new series,
but that still leaves operator skill & technique as a significant variable.
I do not know the methods used to manufacture the 'old' series.
From: David H Craig [mailto:email@example.com]
Sent: Friday, August 15, 2008 1:16 PM
To: HansLG@aol.com; firstname.lastname@example.org
Subject: Re: [TowerTalk] Fwd: Heights Towers Aluminum??
I have no first-hand knowledge of these towers, but I am currently
working with an experienced aluminum welder (military aircraft) on a tower
project. Presuming arguendo this is not a "buttering" problem (cold weld
with no penetration) it sounds as if the completed units are not
heat-treated to bring them back to the original tensile strength.
An example- I asked my welder friend about the practicability of welding
a center-sleeve of 1 1/2" OD 1/4" wall aluminim tube into a 2" OD 1/4" wall
tube so I could have a travel mast with two 8 foot sections that would silde
together & bolt on just one side. He told me the tube stength would be
compromised unless the welded portion was "baked" at the appropriate temp
for 24-36 hours, and that in his shop (a gov't facility with top of the line
gear) the "oven" can only fit 3ft long objects. To wit: "In some
applications it is better to just use hardware and this is one of them".
Why do I get the impression that the critical welded areas of these
towers are not re-heat-treated?
----- Original Message -----
Sent: Friday, August 15, 2008 1:33 PM
Subject: [TowerTalk] Fwd: Heights Towers Aluminum??
>I am glad to get this information. The Height tower I have in my yard just
> now is old. I noticed that some of the weld or the Z have opened and was
> to fix that before I put the tower up. Now I may get all the welds
> before I put it up. I looked at the welds before and wondered if they were
> OK, but as I am not an expert I thought they were OK. The welds that
> brook were
> under high tention after the Z itself bent at these places.
> Hans N2JFS
> From: email@example.com
> To: firstname.lastname@example.org
> Sent: 8/15/2008 2:00:39 A.M. Eastern Daylight Time
> Subj: Re: [TowerTalk] Heights Towers Aluminum??
> Hi all,
> As being the lucky person to clean up the mess left by Owen's tower
> failures, I can tell you first hand that all antenna weights, wind load
> lengths, etc. were passed on to Heights before Owen put them up, anyone
> who knows
> Owen knows he goes by the book and documents!! He was told that his
> was within spec.
> I am no expert on aluminum welding but I do a fair amount about steel
> welding and what I have seen is a failure of welds on his towers.
> Normally, a weld
> is stronger than the surrounding material. If there is a failure, the
> weld is
> intact but metal is ripped away around the weld. A sign of a good weld is
> slight cutting away of material right at the weld. This is the point
> the material starts to melt and becomes one with the welding rod
> material. Some
> of the failed welds on his HF tower that came over first look like they
> poped off, like a cold solder joint.
> His second failure, just a couple of weeks ago, occured at 36 mph as
> measured by his Davis wx station and verified by the local airport which
> only a 31 mph gust. The top section failed right where it went inside the
> section. A leg buckeled in and it was all down hill from there. Once
> as the leg that was receiving all the downward pressure (opposite the
> legs in
> the wind) pushed inward and the Z bracing which is supposed to keep it
> collasping, didn't. I did not see the Z bracing buckle, the welds just
> All the discussions thus far seems to be centered around just self
> supporting foldovers, not crank ups as Owen's was. I'm sure there is a
> between the way the load is distributed down the tower.
> At K8GP, we use a lot of Univeral self-supporting towers that pivot up
> atop our school buses. Our towers take a lot of abuse from being
> (it's only 5 days twice a year!) and riding around on bumpy roads on top
> school buses. Our towers have survived 80+ mph winds and when we have a
> it's usually a fatigued Z brace and NOT at a weld and we only go up 30 to
> I'm not passing judgement on Heights towers or aluminum towers in
> just adding to the discussion of what I saw. For most of us, a tower is a
> pretty good size investment in time and money, and since my tired, old,
> fat butt
> is climbing up, I want nice heavy, thick, galvanized STEEL under me!
> -------------- Original message --------------
> From: <email@example.com>
>> Hi Dick,
>> Unlike K3CB's recent experiences with the catastrophic failure ofboth of
>> Heights crank-up towers (one in dead calm weather and the other in light
> 30 MPH
>> winds), the collapse of the Heights tilt-over tower was the direct
> of an
>> inexperienced tower owner significantly exceeding the maximum dead
>> I suspect he isn't alone in failing to appreciate the importance of not
>> exceeding the dead weight specification for tilt-over towers.
>> ---- Original message ----
>> >Date: Thu, 14 Aug 2008 16:40:33 -0600
>> >From: "Dick Williams"
>> >Subject: Re: [TowerTalk] Heights Towers Aluminum??
>> >I have seen several interesting comments on the reflector concerning
>> >Alum towers; and in fact, I posted a couple myself.
>> >As I mentioned in a previous post, I have three of them and they all
>> >over in the center (80 ft towers with the fold over at the 40 ft
>> >Obviously, weight is a concern, you can't put 400 lbs of antenna and
>> >acessories on the top and expect it to work.
>> >Alum masts certainly help; in fact I have a nice 20 ft, 1/2 inch wall
>> >sitting on the ground that I am not using right now (150 bucks picked
>> >As far as size, I have not found that to be a problem (just weight). I
>> >put the antenna together (or take it down to work on with the boom
>> >to the ground (elements vertical). If the elements are too long, I just
>> >start removing element sections as I lower it down until the boom is
>> >enough to work on.
>> >It is too bad that Glenn Martin Engineering does not produce the
>> >more. It is the similiar to the Hazer except it is on a external track
>> >the side of the tower. I have one on a 120 ft Rohn tower. Have a Force
>> >Mag 620/340N on it with a M2 R2800 rotor. Works great; brings the
>> >right down to the ground ready to be worked on when needed. And all it
>> >takes is a 1/2 inch electric drill to raise and lower it.
>> >All said and done, I like the Heights towers and the Voyager system for
>> >"ground level" antenna work.
>> >Dick K8ZTT
>> >TowerTalk mailing list
>> TowerTalk mailing list
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