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Re: [TowerTalk] Fwd: Heights Towers Aluminum??

Subject: Re: [TowerTalk] Fwd: Heights Towers Aluminum??
Date: Fri, 15 Aug 2008 20:37:34 EDT
List-post: <">>
Heights Tower web site has a technical section and a tutorial on their  tower 
designs. In the tutorial there is a table of tower section specifications  
related to 6061-T6 aluminum.
One specification is the yield strength of the aluminum at 35,000 psi. The  
next entry in the table is the yield strength within one inch of a weld; that  
number is 24,000 psi.
So, their calculations are based on derating the strength of the material  
near a weld. Apparently this is a useful way to avoid the expensive and time  
consuming heat soak procedure mentioned earlier.
Gerald, K5GW
In a message dated 8/15/2008 5:48:08 P.M. Central Daylight Time, writes:

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  ----- 
From: <>
To:  <>
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  
> going
> to fix that before I put the tower up. Now I may get  all the welds 
> inspected
> 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:
>  To:
> 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 
>  specs,
> 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 
> loading
> 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  
> a
> slight cutting away  of material right at the weld.  This is the point 
> where
> 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 
>  just
> 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  
> reported
> only a 31 mph gust. The top section failed  right  where it went inside the 
> next
> section. A leg  buckeled in and it was all down  hill from there. Once 
>  again,
> 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 
> from
> collasping,  didn't. I did not see the Z bracing  buckle, the welds just 
>  broke.
> 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 
> difference
> between the way the  load is distributed down  the tower.
> At K8GP, we use a lot of  Univeral self-supporting towers that  pivot up 
> from
> atop  our school buses. Our towers take a lot of abuse from being 
>  overloaded
> (it's only 5 days twice a year!) and riding around on bumpy  roads  on top 
> of
> school buses. Our towers have survived  80+ mph winds and when we  have a 
> break,
> it's usually a  fatigued Z brace and NOT at a weld and we only go  up 30 to 
>  40
> feet.
> I'm not passing judgement on Heights towers  or  aluminum towers in 
> general,
> 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!
> Terry
>  -------------- Original message  -------------- 
> From:  <>
>> Hi  Dick,
>> Unlike K3CB's recent experiences with the  catastrophic  failure ofboth of
> his
>> 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 
>> result
> of an
>> inexperienced   tower owner significantly exceeding the maximum dead 
>>  weight
>>  specification.
>> I suspect he  isn't alone in failing to  appreciate the importance of not
>>  exceeding the dead weight  specification for tilt-over  towers.
>> 73
>> Frank
>>  W3LPL
>> ---- Original message ---- 
>>  >Date:  Thu, 14 Aug 2008 16:40:33 -0600
>> >From: "Dick  Williams"
>>  >Subject: Re: [TowerTalk] Heights Towers  Aluminum??
>> >To:
>> >
>> >I have seen  several interesting comments on the  reflector concerning
>  Heights
>> >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 
>> >tilt
>>  >over in the center (80 ft  towers with the fold over at the 40 ft  
>> >level).
>> >
>>  >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 
>>  >one
>>  >sitting on the ground that I am not using right  now (150 bucks picked
> up).
>> >
>> >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
> parallel
>> >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 
>>  >low
>> >enough  to work on.
>> >
>>  >It is too bad that Glenn Martin  Engineering does not produce the  
>> >Voyager
> any
>> >more. It is the   similiar to the Hazer except it is on a external track 
>>  >on
>> >the  side of the tower. I have one on a 120 ft  Rohn tower. Have a Force 
>> >12
>>  >Mag  620/340N on it with a M2 R2800 rotor. Works great; brings the 
>>  antenna
>> >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
>> >
>> >
>> >
>>   >_______________________________________________
>>  >
>>  >
>> >
>>   >_______________________________________________
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