Folks,
I agree fully with Paul.
When building and maintaining the N6IJ contest station with which the Army
blessed us at the site, with numerous 70' wooden poles, mostly installed in
the 60s, I investigated the safety and capacity of wooden poles. The
reference manuals for wooden poles that the Army and Power industry had,
amazed me.
I recall that the Class 1 or class 2 poles that we had, could withstand a
1200 lb HORIZONTAL load near the top of a 75 ft pole, buried 11 ft in the
dirt, with no concrete necessary for a foundation.
(This is assuming the particular dirt we have at N6IJ will withstand the
loading. which we never did the testing. The pole strength was awesome.)
I wonder how much wind on, say a 15 square foot antenna would be required
to push, say 800 lbs? Take into account the additional square area, of the
pole, about 12" dia. Local line men told me that under good soil
conditions, and maintenance (preservative injection, as necessary) the
tower base stays structurally sound easily 40 years.
Some soils/biologics can cause more rapid deterioration. Those at N6IJ were
of that age, and many had little injection taps near the ground level that
the crews used to periodically inject additional preservative. (See
http://www.n6ij.org for antenna farm pictures )
If you need to determine how deep an existing pole is buried, the 75 footers
have a data plate mounted the standard 15 ft above the base. Shorter poles
sometimes have the data plate mounted 10 ft above the base. A rule of thumb
from the manuals, on how deep to bury the pole, assuming the earth is
capable of strong support, and is properly tamped, was 10 percent of the
total length, plus 2 ft.
All of our poles had pole steps, making them easy and safe to climb. We
were priveleged to have been given permission to raid a surplus yard at Ft
Ord for pole hardware which we were able to do minor additional assembly and
fabrication to make mounts and supports for beams and rotors. Such hardware
is probably not cheap to buy, but in small quantities would not be a
significant fraction of the overall iinstallation.
A major manufacturer of wooden poles is McFarland.
http://www.ldm.com/
They have a very good website, for determining size, weight, cost, for
poles.
I priced from McFarland, about 9 years ago a Class 1 (thick) 120' treated
preserved pole, with climbing step holes drilled, and delivery costs and
came up with a quote total of $7000 delivered to the site (horizontal on
ground, at site, erection extra) It would easily hold ANY ham beam antenna
at that height, without guys or concrete. (assuming good structural earth)
The delivery was from various Forest locations, depending on destination
location and they charge by the mile. (120 ft pole has obvious difficulties
with transportation and McFarland had to plan routes carefully in advance,
and I think it took 2 trucks. I think the pole cost was $3K, and transpo
costs were around $4k from Idaho to Monterey. The weight was quite awesome,
I think around 10K lbs. All details can be found at McFarland's website.
So, add some additional costs, and say, you could easily get a massively
strong 120 footer tower installed for under $10K, I think that is a lot
less than a steel tower.
73, DX, de Pat AA6EG aa6eg@hotmail.com;
Skype: Sparky599
Moon or Bust!--Jamesburg Gang Rides Again!
>From: "Paul Darwactor" <phd73@mindspring.com>
>Reply-To: phd73@mindspring.com
>To: towertalk@contesting.com
>Subject: [TowerTalk] Utility Poles
>Date: Sat, 28 Apr 2007 03:02:22 -0400
>
>For those who think a utility pole has no utility for ham use, I would
>submit the following.
>
>I am using a class 3, 65 foot utility pole that was installed new in 1984.
>It is pressure
>
>treated and requires no maintenance. For the past 23 years it has supported
>stacked
>
>beams totaling 25 square feet of wind load with out concrete foundation or
>guy wires.
>
>It's condition is as solid today as the day it was installed. I was told by
>the company that
>
>provided it that I could expect 100 years of useful life. I don't expect to
>be around long
>
>enough to test the warranty. Should I need to remove it I can employ the
>truck that
>
>installed it to spend about 30 minutes to remove it and refill the empty
>hole. New owner of
>
>the QTH will never know it was here ! For my money it beats the best of the
>many steel
>
>and aluminum towers I have owned over my past 54 years in Ham Radio, hands
>down .
>
>Just my severely devalued dollars worth. YMMV.
>
>73 de Paul W8ZD.........................................
>
>
>Paul Darwactor
>phd73@mindspring.com
>Why Wait? Move to EarthLink.
>_______________________________________________
>
>
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|