On 1/30/2015 10:43 PM, Bill Aycock wrote:
The tower broke, not the base. I've been up many a 40 footer set on a
dirt base...with temporary guys, which I installed. There are only a
couple people who I'd trust with temporary guys and I use clamps. I'm
very poor at tying knots. N8ERF just shakes his head after looking at
my knot tying skill. <LO>
Two of us took down a 90' American Steel for a SKs wife.. Those things
are like a wet noodle with a soft steel alloy. In my younger days I
climbed a lot pf them. They are the kind where you keep your body
straight and real closer to the tower. None of this throwing your weight
around. I've never seen all the sections on a 90 footer stay straight
for long. The legs actually "belled out" between the two bolts in the
legs on the bottom 2 or 3 sections. We took the 6 sections down,
one-at-a-time, but we just pulled the pin on one side and walked the
bottom 30 feet down. At only 30 feet and nothing on it, I could walk it
down alone, but two sets of hands just feels a lot more secure.
When I took my old tower down, I had to shake my head after inspecting
those sections. Those are the ones where over guying is not advisable.
The weight of 1/4" steel guys, plus proper tension will exceed the
ratings of the tower.
73
Roger (K8RI)
Roger--
It is, indeed a sad story, but do you know if the tower was installed
with the proper base for Unguyed use?
If not, why should we be surprised?
Bill--W4BSG
-----Original Message----- From: Roger (K8RI) on TT
Sent: Friday, January 30, 2015 8:14 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] [Bulk] Rohn 25G tower permitting
As to unguyed 25G at 30 feet plus. I have a friend who was taking a 25G
down. He was down to the last 30 feet with the last set of guys removed
when it broke. It went over with him fastened to it. After months in
the hospital and multiple surgeries he will never be the same.
I don't think anyone knows for sure why it broke, but when he hit, he
was on the bottom with the tower on top.
73
Roger (K8RI)
On 1/30/2015 1:56 AM, Jack Brindle wrote:
Rohn has a section in their catalog for unguided towers which
includes Rohn 25. They call for something like 2.5’ x 2.5’ x 4’ of
concrete for the base. I’m not sure I really want to be up 35 feet on
that, but it has been in their literature for as long as I can
remember. I am sure many folks have built one of these, and would
love to hear opinions on ways to make it safe. I suspect this is what
the original poster was referring to. Not all of us can have tall
towers - sometimes 35 feet will have to do, and extensive guy systems
can be problematic on small city lots. So, the question really is how
do we put this stuff up and make it safe? Is this where you were
heading, bcarling?
73,
Jack B, W6FB
On Jan 29, 2015, at 8:19 PM, Roger (K8RI) on TT
<K8RI-on-TowerTalk@tm.net> wrote:
On 1/29/2015 6:57 PM, Grant Saviers wrote:
My 140' Rohn 65 base is 4x4x2 ft. PE engineered. So 3' of concrete
is a bit much, check the Rohn catalog. The most important thing
with a base in concrete is the legs go through it and into some
gravel for drainage. I've seen many legs split by water freezing in
them.
Or use a pier pin base with solid lefs. Easy to make and not expensive.
73
Roger (K8RI)
I wouldn't go as far as "3/4 ply and broomsticks" but the loads
from 30' won't need much of a base for 2000psi soils. It's all in
the catalog.
Grant KZ1W
On 1/29/2015 10:10 AM, Wilson wrote:
I think you are being led around by the short hairs.
How did you decide a 27’ tower needed to be in 3’ of concrete?
For practical purposes there is no bending and no horizontal load
at the base of this tower, assuming it is guyed, of course, which
–25 must be.
You could stand 30’ of 25 on a piece of 3/4” plywood and three
broomsticks and have a fine installation!
The guywire and anchors are your real design hotspots, so a
reasonable estimate of overturning moment is necessary.
With it, you figure the worst guyline load and that gives you an
anchor capacity requirement.
You may have the perfect place for some screw in anchors, or an
ideal place to display some heavy yard art!
Yes, you’ll have a little horizontal load due to drag on the tower
itself, if it’s in the clear, so maybe use rebar or pipe instead
of the broomsticks.
I have a 2’ square pad and a tilt plate for mine (40’) and it’s
overkill. The tilt plate is great for antenna maintenance.
And are you required to tell them all about the antennae to be
installed?
The less you tell them, the better, since you’ll be changing
eventually anyway.
WL
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73
Roger (K8RI)
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73
Roger (K8RI)
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