[TowerTalk] Choice of aluminum

[K8RI]

On 10/13/2012 8:02 PM, Jorge Diez - CX6VM wrote:
> Hi Rudy,
>
>
>
> You are lucky!, I am considering something for CW/SSB J
>
>
>
> There´s some commercials self supporting towers. Also a Rohn 25 is good for
> a guyed tower. My problem is shipment cost and handling.
>
>
>
> So looking for instructions about how to build one J

If it's for a tower you probably want to avoid Aluminum.
A mast a bit short of 66 feet should work well.  The larger the diameter 
the more bandwidth. You can get or make verticals that are unguyed, but 
if used in an array they do tend to wobble around quite a bit. Small 
diameter on top to reduce the effects of wind load, BUT that means less 
band width.  If you have the room and can get some pieces of Lexan or 
Plexiglass you can make rings for guy attachment. Then shorten the mast 
a bit and add a top hat which will also add a little bandwidth.    I 
have used 3/16" Poly rope on  a set up like this for guying an AV640 
multi band vertical mounted on a mast.

The reason I'd recommend against trying to build an aluminum tower is it 
takes some one with skill (which you or a friend may have) running a TIG 
welder. Each weld tends to take the temper and strength out of the 
Aluminum at the weld points.

OTOH the old Aluminum towers that came in 8' sections were a very soft 
alloy and not meant for climbing.Those make great verticals, although 
they need guying above 32 feet in height.  Those were light enough that 
one man could easily stand up a 40 footer without straining.

If you are good at TIG welding and have a welder you could build 
something akin to one of these, but as a single unit.  Used as an 
insulated base, vertical the strength is not nearly so important. Of 
course you still don't want it to fall over in the wind.


73 and good luck,

Roger (K8RI)


>
>
>
> 73,
>
> Jorge
>
> CX6VM/CW5W
>
>
>
> De: Rudy Bakalov [mailto:r_bakalov at yahoo.com]
> Enviado el: sábado, 13 de octubre de 2012 21:46
> Para: Jorge Diez - CX6VM; TexasRF at aol.com; towertalk at contesting.com
> Asunto: Re: [TowerTalk] Choice of aluminum
>
>
>
> Jorge,
>
>
>
> This is a great question that has been on my mind for a while. I was very
> tempted to try to model it, but never found the time to do so. I also
> thought that all I care about is the CW/RTTY portion of 80m.
>
>
>
> That said, I decided to see what DX Engineering offers on their site for 80
> m. Two very interesting observations from the 80m vertical installation
> manual:
>
>
>
> 1) they use very small size tubing, not even close to what I am considering
> (my current 40m vertical uses better tubing!!!)
>
> 2) they claim a very wide bandwidth
>
>
>
> So if their 80m verticals are half as good as they claim, the much beefier
> size tubing I am considering should do very well.
>
>
>
> Rudy N2WQ
>
>    _____
>
> From: Jorge Diez - CX6VM <cx6vm.jorge at gmail.com>
> To: 'Rudy Bakalov' <r_bakalov at yahoo.com>; TexasRF at aol.com;
> towertalk at contesting.com
> Sent: Saturday, October 13, 2012 7:36 PM
> Subject: RE: [TowerTalk] Choice of aluminum
>
>
> Hello Rudy
>
> What´s the bandwidth of this verticals compare with towers?
>
> 73,
> Jorge
> CX6VM/CW5W
>
> -----Mensaje original-----
> De: TowerTalk [mailto:towertalk-bounces at contesting.com] En nombre de Rudy
> Bakalov
> Enviado el: sábado, 13 de octubre de 2012 21:04
> Para: TexasRF at aol.com; towertalk at contesting.com
> Asunto: Re: [TowerTalk] Choice of aluminum
>
> Gerald,
>
> Thanks for the comprehensive answer. I didn't realize that 6061-T6 is more
> expensive than 6063 as I was looking online prices in chunks of 12 and 24'.
>
> Just for kicks I prices a 4-Square set of verticals made of 24' sections of
> 3", 2.5", and 2.0", 0.25" wall thickness. $2,300 delivered for the set.
> Doesn't look that bad compared to dealing with towers and tower crews.
>
>
> Rudy N2WQ
>
>
> ________________________________
> From: "TexasRF at aol.com" <TexasRF at aol.com>
> To: r_bakalov at yahoo.com; towertalk at contesting.com
> Sent: Saturday, October 13, 2012 6:36 PM
> Subject: Re: [TowerTalk] Choice of aluminum
>
>
> Hi Rudy, 6061-T6 aluminum has a yield strength rating the same as 6063-T832
> that is sold by Texas Towers and others.
>
> The 6061-T6 costs more than 6063-T832 because of the extra
> heating/quenching steps needed to reach the rated yield strength. 6063-T832
> reaches the rated yield strength by work hardening the material in the
> drawing
> process.
>
> If you want a self supporting vertical, then you would need to go through
> the same process as designing a 80 meter beam element with most of the
> material
> weight left out of the calculations. Just as a guess I would expect the
> bottom
> section to be about 4" diameter with a .25" wall.
>
> This is not a trivial structure! Please proceed with caution!
>
> If you want a guyed vertical, there are a number of them that have been on
> the air long enough to think about duplicating one. W5UN is one that comes
> to
> mind.
>
> 73,
> Gerald K5GW
>
>
>
>
>
> In a message dated 10/13/2012 4:09:30 P.M. Central Daylight Time,
> r_bakalov at yahoo.com writes:
> I was  wondering if anyone can help me select the right material for
> full-size 80m  verticals. My questions are as follows:
>>
>> 1) metalsupermarkets.com offers
>    6061-T6 aluminum, but not T8. Is there a difference between T6 and T8 for
> my
>    purpose?
>> 2) Should go for the 0.125 or 0.065 wall thickness?
>> 3) Is 1"
>    tubing OK for the topmost segment? Too stiff for the wind at 70'? Not
> strong
>    enough?
>>
>>
>> I am aware that many ham stores offer 6061-T8 tubing, but I
>    do want to buy it local in VE3, close to my QTH, in 12' lengths (instead
> of
>    6') and avoid shipping complications due to length or clearing
>    customs.
>>
>> 73 Rudy
>    N2WQ
>> _______________________________________________
>>
>>
>>
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