On 10/13/2012 8:44 PM, Grant Saviers wrote:
DX Engineering sells Yagi-Mech which calculates wind loads for yagi
elements. Generally, gravity is less stress than wind so you can get
some estimates of what is needed for diameters and wall thickness for a
self supporting vertical. (zero wind will reveal the gravity stress
levels).
A problem with stock tubing from mass metal suppliers is a .250 wall is
.250 +/- some tolerance which may preclude telescoping at the stepped
diameters.
That's not "May Preclude"telescoping, stepped diameters in half inch
steps and 1/4" wall should not fit! Period. If they do fit they are mis
sized because the numbers would give you what is called an interference
fit. With Aluminum you'd need something like never seize(DP?) and the
pieces would have to be pressed together.
A word of warning: I don't know your altitude, but for those who live in
more Northern (and Southern climates)and you are next to Argentina... If
you machine a piece to fit tightly into the base of the vertical and you
live in an area where freezing occurs even on occasion, put in plenty of
drain holes. Aluminum and steel are no match for freezing water.
My daughter was down there 6 months ago, ice climbing in Argentina.
You won't know until you try it for each tube. Note that DXE
(and Texas Towers) sells tube made especially for telescoping and the
walls thickness is reduced appropriately so the draw tolerance can be
accommodated. I've asked DXE for longer lengths than catalog - no
dice. Apparently, they have to order mill lots to get the thinner wall
and have it cut to length by the supplier.
Either they or maybe Texas Towers have 12' lengths which must go motor
freight and are still only half lengths as standard mill lengths are 24
feet. I've seen the 12 footers advertized with the freight warning.
Normally 12' is plenty long for even 40 meter elements and you can
build splices for the boom. The same goes for verticals. You either
need a flat bed truck or pick up with pipe racks to move the stuff. I
live on a short street that one of the big freight trucks can only back
as far as our driveway. There is absolutely no way they can get into the
driveway even though its wide and paved. They can't make the turn off
the street into the drive. They can barely make the turn onto the
street. Also, standard mill finish is not the smooth, shiny, reflective
shine we see on the stuff specifically for antennas.
I usually have stuff delivered to the local airport and then hire a tilt
bed used for hauling cars and trucks. That's about $80 a shot and
considered very cheap. The steel and aluminum suppliers usually deliver
via a flat bed for sheet, tube, and plate and do so free for good sized
loads or if I'm willing to wait until they have a load headed this way.
Of course when you consider the time it took to get the milling
machine off the big truck and onto the tilt bed made the expense well
worth it. Then I made a platform out of 2 X 12's and used 1" steel pipe
rollers under it. It still took me over a full day to get the mill from
the front of the shop to the back. I've been running conduit (EMT) from
the contactor box to the breaker box for the last two days. I only have
one short piece to go from the breaker box to the long run, but it has 3
bends...2 shallow and one 90 degree and bending conduit is not my best
suit!. Now I need a "soaper" to feed the cables into the conduit while
I pull. Hope to get that done tomorrow, Sunday afternoon.
I may just let the cable hang down to the breaker until I can get to
town and pick up another piece of 3/4" EMT.
One of the problems with the big trucks is they completely block the
street or road while unloading. There is also the problem of unloading
really heavy stuff. They don't like to be setting there while you
unload 20 or 30 pieces of tubing
The only way I can get it is mill lots, or wait and get it as part of a
lot so I don't have to pay the extra. A mill lot is a lot of tubing.
Also most of the sizes are for antenna elements and are not structurally
sound for unguyed verticals.
I've found that the
"guarantees telescoping" wall thicknesses are hard to find in stock at
Jorgensen, Tube Service, Thyssen, etc., but it is always worth a call as
they can check the entire USA inventory online. You always have the
choice of machining some couplers from very thick wall material, also
known as Holobar. The good news is onlinemetals.com stocks a lot of
sizes and will sell it in 12" lengths.
My former QTH 80m top loaded vertical failed from fatigue after 6 years
since I guyed it at the top and 50% - a bad idea as it oscillated like
crazy in winds greater than 15kts. So plan to guy at heights that won't
couple oscillations between sections through guy points. My failure
point was like it was laser cut. Note that Al has NO threshold fatigue
stress level, whereas steel has a threshold that if not exceeded the
fatigue life is infinite.
Consider what it will take to erect the mast - a 50% height falling
derrick will likely work or a sign truck crane might be able to handle
the weight.
A mast and hand winch for a falling derrick will also work, but it can
be slow and tiring.
Or rent a 40' 4WD boom lift as they usually have 500#
capacity so you and the mast hopefully won't exceed that ;-) . They're
a lot of fun/exciting and easy if you go slow and get the delivery guy
to give you the basic operating course.
Many companies will not allow any one to operate their equipment other
than their employees due to insurance. I used to operate the things
where I worked (before going to college) but my license has long since
expired. One place locally would let me run theirs, but it was well over
$1000 for the week end. Another place 20 miles away was just over half
their price, but I had to use their operator and it was "portal to
portal" for both the machine and operator.
Grant KZ1W
On 10/13/2012 5:02 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
How about TV towrs? they are generally light and fairly cheap, but I
don't know how they'd go in that part of the world.
A steel tower will work well for an antenna that size, but they do
require some equipment to put up. 60 feet should go up in one push, but
I'd not want to go much taller than that. I've even climbed a 90 foot
TV tower (that was well guyed)
it depends on what is available in your area. The problem with building
your own tower is that pipe is generally far too heavy (as well as soft)
and once welded up they need to be galvanized or well painted, inside
and out.
73 and good luck,
Roger (K8RI)
73,
Jorge
CX6VM/CW5W
De: Rudy Bakalov [mailto:r_bakalov@yahoo.com]
Enviado el: sábado, 13 de octubre de 2012 21:46
Para: Jorge Diez - CX6VM; TexasRF@aol.com; towertalk@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@gmail.com>
To: 'Rudy Bakalov' <r_bakalov@yahoo.com>; TexasRF@aol.com;
towertalk@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@contesting.com] En nombre de Rudy
Bakalov
Enviado el: sábado, 13 de octubre de 2012 21:04
Para: TexasRF@aol.com; towertalk@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@aol.com" <TexasRF@aol.com>
To: r_bakalov@yahoo.com; towertalk@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@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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