Hi Alton,
I don't know if you remember me and the ruckus I caused last time on the
list by "calling it like I see it" in relation to a tower installation on a
webpage, but I'm going to stick my neck out again and respond. I'm a
professional lighting technician (not an engineer or tower installer) and
have received lots of formal training in fall protection, rigging safety,
and hazard recognition/avoidance. You may very well receive emails saying
to ignore everything that I say. If you do get any of them from certified
engineers who can back up their words with something other than anecdotal
evidence, I would like to see them, i.e., the "hams use climbing belts all
the time for fall protection and no one gets hurt" argument doesn't change
the fact that thousands of pounds of force on someone's pelvis will destroy
it.
We may be "amateur" radio operators, but the laws of physics still apply
equally to us and the word "amateur" won't help you sleep at night if a
shortcut kills someone.
Best of luck to you!
Jason
KC0ERG
On 1/8/2006 at 12:23 PM Alton J Drummond Jr wrote:
>Hello All,
>I am a Amateur Radio operator and I am installing a 65ft Rohn 25G...
>I want to raise the guys so they don't "Clothes Line" anyone, and I can
still walk around the yard.
One word: "DON'T"
More words: "...unless you can get an engineer to sign off on your
modifications."
Rohn has highly paid structural engineers that design all of their
products. These people put their professional reputations and livelihoods
on the line when they sign off on a project or design. If something that
was manufactured and installed according to their plans fails and kills
people, their lives are essentially over because they will be looking for
another line of work.
Change their plans, change the failure point of the tower and installation.
Period.
(Granted, engineers vary just like everything else. A certain theatre in
Branson, Missouri used to "shop around" to find engineers who would approve
the massive loads they are putting on what is essentially a pole barn
building. It was originally designed to hold the weight of PAR can
fixtures, not moving light fixtures that weigh hundreds of pounds. If the
"newest, latest, and greatest" fixtures overload the previous engineers'
calculations, they find another one who will approve it for more money than
you or I would ever be able to spend on a project.)
> I was thinking a 9' or 12'steel pole 3 ft in the ground with cement,
JOKE ALERT:You might be able to save yourself some time, trouble, and money
by buying an already destroyed tower. :-)
Please don't take the following the wrong way. I am merely explaining the
train of thought behind my opinion.
Each part of the installation, while being connected in one system, is
still independent of another part. Your tower is going to exert a static
force on the guy wires just by being in the air. That force will increase
dramatically as the wind blows and gusts. The guy wires will transfer that
force to their anchor point. The force exerted by the tower on the guy
anchors will not change with the design of the anchors. The anchors'
ability to withstand the force WILL.
Think of the anchor in the ground as that first "applied physics
educational tool" that most of us encounter: a teeter-totter on the
playground. (Of course, there's so much more to that analogy that it takes
years in college to learn it all, but it's close enough.) Ground level is
the fulcrum.
Every foot above ground level adds significantly to the amount of anchor
you need IN the ground to keep the anchor in place. High rise office
buildings don't have huge underground parking garages merely for
convenience's sake. They are there to wedge the building into the ground
and counteract the wind trying to push the building over.
Your 9' steel pipe above would exert significant force on the 3' buried in
the ground. The 12' would exert MUCH more force on the part of the system
that's trying to keep your tower in the air.
Now compare that to a cube of cement 2' on each side with the same force
exerted directly at ground level. Which one will keep your tower in the air
better?
>I want to do this right, any and all suggestion,
Don't do anything other than a plan approved by an engineer. You're in the
hot zone of being near the coast, so this is even more important. The life
you save may be your own or one of your family members.
The "That Looks About Right" Engineering Principle kills people.
- Jason - KC0ERG
========================================================
http://jason.creager.com kc0erg@qsl.net Las Vegas, NV
All responses subject to the terms of
http://jason.creager.com/disclaimer.html
http://jason.creager.com/uros.html - The #1 Mali Uromastyx Info Source
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