Re: [TowerTalk] My Tower cost

["Tower (K8RI)" <tower@rogerhalstead.com>]

> On Aug 25, 2004, at 12:44 AM, Tower (K8RI) wrote:
> > Not really. OTOH all tower installations depend on luck to some extent no 
> > matter how well engineered.
>
> Only to the extent that the actual weather conditions meet the engineering 
> data. If you design for 70 mph and get 170 mph winds, nothing will stand 
> unless you are lucky.
>
> >   For the winds of 70 MPH and only 40 foot towers using 1/8th inch steel 
> > guys anchored in clay was sufficient.  This was also back when tower 
> > installations were seldom engineered.
>
> 1/8th steel guys were never sufficient. "Anchoring" them in clay and 
> attaching them 8 feet off the ground was never sufficient -- in fact 
> closer to not having guys at all.
Ahhh... No, the old "fence post" which is still often used had the guys 
connected to the base right at the ground. I used one set at the top and 
another around 12 feet down. They were very effective.

> While such shoddy engineering practices may have been common practice 
> years ago, they are not advisable today.
>
> > OTOH, given the same set of circumstances I'd have no qualms about doing 
> > those same installations again in the same locations.  Would I do them 
> > here? No as there is no free space for them to fall, IF they fell.  Had 
> > they fallen I'd have only been out the antenna. The towers were either 
> > cheap or free.
>
> What if they hit someone during the fall? What if they fell while they 
> were being climbed?

Who would they hit?  This was out in the country and no one would be in the 
garden or out in the yard during high winds any way.  Those would occurr 
during thunderstorms or during the winter.

Climbing them was like climging my 45G, but not as convenient.  The old 
American Steel had cross rungs every two feet. They were solid when 
climbing.

> > What do you see as a safety issue?
>
> Improper tower base. Inadequate guy wires. Inadequate guy anchors. 
> Overloading of tower.

The tower base was the one that came with the towers and was designed for 
dirt.  Set in clay they never moved.
Yet they withstood 70 MPH wind gusts on quite a few occasions over something 
like 12 to 15 years with no damage.

> > Back then there was no such thing as properly, or improperly engineered 
> > towers way out in the country, at least not little 40 footers.That was 
> > also over 35 years ago.
>
> Today there are such concepts.
>
> > The only antenna I ever lost was a tripod mounted TV antenna in the 
> > center of the roof. It pulled the lag bolts right out of the backing 
> > plates.
>
> Lag bolts!

Certainly. There were 3 per leg.  That was the recomended mount for the TV 
tripod.  They didn't even recomend the 2 X 6 backing plates I used.

> > The towers with the big KLMs and the Wilson suffered no damage. That was 
> > covered. The adjuster took one look at how it had been installed and I 
> > got paid.
>
> You are one lucky fellow.
>
> > Some one mentioned towers and the concrete as being structures.  Here in 
> > Homer Township ham towers 80 feet and under and not considered 
> > structures, nor are their bases. They require no building permit and the 
> > county doens't even want to bother inspecting them.
>
> Just because they don't require inspection is not reason not to do the job 
> right.

I'm just saying you can pour as much concrete into the base as you wish 
without any permit in this area.
You can see how I installed mine which did require an inspection.

> Again, I'm all for being cheap, but not at the expense of safety. That's a 
> false economy.

Today, in many areas I see ham tower instalations that make my old 
installations look over engineered.  30 and 40 foot towers I wouldn't climb 
even when I was younger.
Fortunately I've been asked on quite a few occasions what I thought of what 
some one was planning and was able to give some input.  Invariably these 
were not the 30 or 40 towers, but big heavy towers or the smaller 25Gs going 
to 90 feet plus.

In nearly every instance they had good basically good ideas, but had 
neglected at least one issue that would render the system unsafe.

In one particular instance a ham was going up 100 feet with 25 G and 
following the book for guying. Good base, good anchors, and it was going to 
support a substantial 144/440 array within it's capabilities.  He wanted to 
reduce the twisting moment on the tower and was planning on putting the 
rotor down at the base where it would be easy to get at and also reduce the 
twisting moment.

Unfortunately mounting the rotor just two feet above the base puts all that 
twisting moment against a short piece of tower that is pretty much rigid and 
eliminates the spring in the overall tower. Not a probelm with small 
antennas, but it could have been a problem with the array.  The big problem 
came from the mast that went from the rotor to the antennas. He was using 
chrome molly tube which was a good idea, BUT it was 1 1/2 inch tube with 
half inch wall.  I could barely lift one end of a 20 foot section off the 
ground. Each 20 foot section weighed well over 300#. He had 6 sections for a 
total of 1800# in addition to the tower weight and guy tension. He had 
planned on using 1/4 inch EHS.

We went through the calcs a week of so back as to the pressure on the base 
and even the little 25 G can support phenominal loads when they are evenly 
distributed and in the vertical plane.
OTOH many of the TV type towers used for ham antenna systems have no where 
near that strength.
This tower could have supported the additional load and even the extra 
tension from the 1/4" EHS, but the specs call for 3/16" EHS at 3 levels.  He 
was still within load limits, but any shift due to wind allowed by the 
catenary could put a single leg beyond the design limits.  This doesn't take 
into sonsideration the extra 1800# on mass added to the twisting moment 
transfered to the base.  Nearly all antennas stend to swing a bit in wind 
and nearly all rotors have at least a little give.  With the spring in the 
tower unavailable to take up the torque, I doubt that base would have 
survived 30 MPH winds if the array started to oscillate.

OTOH all he needed to do was install a larger concrete base so it supported 
the rotor on stand offs.  It would have removed the extra load and all the 
twisting moment of the antennas and mast from the tower base.

I find, in general, it's the little things in the larger systems that tend 
to scare me rather than the little systems.  True I may not be willing to 
climb most of the light duty systems, although the "dirt base" rarely plays 
a part in that. More often than not it's the way the tower is assembled, its 
condition (rust, bent, cracks), or loose guys.  Most of those little systems 
can be put up with no climbing which is good as you'd never get me on one.

The taller and heavier the installation the more critical the safety issues.
A group of us recently took down a 32 foot tower with a small tri-bander on 
top. It was... well... not exactly a solid instalation. The tower was 
similar to an HBX series The bolts had loosened, the guys were very loose, 
and it didn't have a dirt base, the bottom was just set into the sand about 
a foot. Basically it was like a wet noodle. That "system" had been up over 
15 years and withstood winds that took down nearby trees.  Six of us, more 
or less just picked it up and laid it down over a step ladder to remove the 
tribander.  Had it fallen over in the winds the most that would have 
happened would have been his wife's flowers.

OTOH that 25 G installation could have cut a house right in two.

I have some photos of a 60 American Steel tower that went down due to the 
high winds in a blizzard about 20 years ago.  The tower was guyed at two 
levels and bracketed to the peak of the roof some 30 feet up (two story home 
with high pitched roof) It  had a tribander, and some VHF antennas on top. 
It was guyed with the typical 3/16" hardware guy line which is soft steel. 
A set of guys broke and it bent the tower right over the top of the house 
and left the top section with antennas hanging down the north side of the 
house.

I went up to the peak and sawed the tower in two so the top part could slide 
off the roof.
BTW, there was no damge to anything other than the one tower section and the 
antennas.
It didn't even hurt the roof.

If I had to guess, I'd say that the installations most of us have that 
frequent this group and not typical of ham installations in general.  Were I 
to bet, I'd say that maybe 10% are actually engineered while the other 90% 
are much closer to what I've described.

I purchase good materials and adhere to the books. I also use good safety 
equipment and pratices.

> > N833R, World's Oldest Debonair (S# CD-2)
>
> I assume this is a Beechcraft airplain. Cool.

First one off the assembly line. 
http://www.rogerhalstead.com/833R/833R_frame.htm
The airworthyness certificate says September 11, 1959.  The airframe log 
shows 30 hours of pre production flight testing.  It still has slightly less 
than 4000 hours and I've put over a 1000 of those on it.
It's a hybrid consisting of a V-35 fuselage, but with a 33 empenage 
(conventional tail) grafted on.  It was called a 35-33 for the first few 
examples and then changed to a 33.

Roger Halstead (K8RI, EN73 & ARRL Life Member)
N833R, World's Oldest Debonair (S# CD-2)
www.rogerhalstead.com
> Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@arrl.net
> Quote: "Not within a thousand years will man ever fly!"
>             -- Wilbur Wright, 1901


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