PRB-1 and CC&R's
 

"Phil Kane" wrote in message
...
On Wed, 21 Mar 2007 22:11:47 EDT, "Dee Flint"
wrote:

Does anyone have information on this? Although the speaker was supposed
to
be an expert, I'd be interested in some independent information on this.

See my earlier post. The study was made by the engineering firm that
designed the TV transmitting antennas on the Empire State Building in
New York City - the name escapes me, though.
--

73 de K2ASP - Phil Kane

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon

e-mail: k2asp [at] arrl [dot] net


Very interesting. If you should happen to remember who it was, please let
us know. Or if you happen to think of more tidbits of information that
would help a person find the info that would be great too.

Dee, N8UZE

PRB-1 and CC&R's
 

Phil Kane wrote in
:

There was a study made of commercial tower failures several decades
ago that showed this, and I've seen this first hand in some of the
broadcast and comm towers affected by the 1989 Loma Prieta earthquake
in the San Francisco area.

Whether the local building official is sharp enough to know this is an
exercise left to the applicant....!

The most likely failure scenarios are very true, but there is a
credibility issue in these matters. We can speak of failure modes until we
are blue in the face, but a simple worst case fall radius is easy for non-
engineering types to understand.

- 73 de Mike KB3EIA -

PRB-1 and CC&R's
 

Phil Kane wrote:

As we all (should) know, towers rarely, if ever, fail in "stick fall"
mode where the fall zone radius is equal to the tower height. The
usual fall mode is a buckling collapse along the length of the tower
resulting in a fall radius of about 10-15% of the tower height.

My lot is 100' on the short side. Using that statistic, assuming I placed a
tower in the center of my lot, I should be able to get a permit to erect a
333' (50' / 0.15) tower. Somehow, I don't think I have a snowball's chance
in Hades of getting a permit for it. Oh well... it was a nice dream! hi

73,
Bryan WA7PRC

PRB-1 and CC&R's
 

Mike Coslo wrote:
Phil Kane wrote:

There was a study made of commercial tower failures several decades
ago that showed this, and I've seen this first hand in some of the
broadcast and comm towers affected by the 1989 Loma Prieta earthquake
in the San Francisco area.

Whether the local building official is sharp enough to know this is an
exercise left to the applicant....!

The most likely failure scenarios are very true, but there is a
credibility issue in these matters. We can speak of failure modes until we
are blue in the face, but a simple worst case fall radius is easy for non-
engineering types to understand.

And all the logic in the world won't help if the local building official
insists on using the worst-case scenario or local laws demand it.
Frankly, if I was the local building official, I would use the
worst-case scenario. The primary responsibility of a building inspector
is public safety, and invoking the worst-case scenario seems appropriate
in this case.

73, Steve KB9X

PRB-1 and CC&R's
 

"Steve Bonine" wrote in message
...
Mike Coslo wrote:
Phil Kane wrote:

There was a study made of commercial tower failures several decades
ago that showed this, and I've seen this first hand in some of the
broadcast and comm towers affected by the 1989 Loma Prieta earthquake
in the San Francisco area.

Whether the local building official is sharp enough to know this is an
exercise left to the applicant....!

The most likely failure scenarios are very true, but there is a
credibility issue in these matters. We can speak of failure modes until
we are blue in the face, but a simple worst case fall radius is easy for
non-
engineering types to understand.

And all the logic in the world won't help if the local building official
insists on using the worst-case scenario or local laws demand it. Frankly,
if I was the local building official, I would use the worst-case scenario.
The primary responsibility of a building inspector is public safety, and
invoking the worst-case scenario seems appropriate in this case.

73, Steve KB9X

No it isn't appropriate. There are telephone poles near my house that if
they were to fall will destroy my house. My neighbors TREES could do the
same. Yet most people do not see these as significant hazards. They are
used to seeing them so do not think of them as hazards.

I lived in one place where a tree next to my garage had a serious case of
heart rot (hollow top to bottom). The tree was all but dead but the owner
would NOT remove it because it was still "alive" (i.e. it had about a dozen
leaves on one branch on one side of the tree). I could not find a way to
force the owner to get rid of the tree. All I could do was to move my car
out of the potential damage area when strong winds came up.

As far as towers go, what is appropriate is that it be required to be
erected per the manufacturer's design guidelines.

Dee, N8UZE

PRB-1 and CC&R's
 

"Dee Flint" wrote:

No it isn't appropriate. There are telephone poles near my house that if
they were to fall will destroy my house. My neighbors TREES could do the
same. Yet most people do not see these as significant hazards. They are
used to seeing them so do not think of them as hazards.

Rather than looking at this from the negative, let's look at it as a real
business possibility.

How about designing a series of towers that look externally like
tree-trunks? Or, developing camoflauge that hams wrap on the outside of
their towers which disguise them (the towers, not the hams) as big oak
trees?

Then, likewise, we can design a series of multi-element beam antennas which
look like tree branches, complete with fake leaves!


The possibilities (and income potential) is endless!

73
kh6hz

PRB-1 and CC&R's
 

"Dee Flint" wrote in
:


"Steve Bonine" wrote in message
..

some snippage

And all the logic in the world won't help if the local building
official insists on using the worst-case scenario or local laws
demand it. Frankly, if I was the local building official, I would use
the worst-case scenario. The primary responsibility of a building
inspector is public safety, and invoking the worst-case scenario
seems appropriate in this case.

73, Steve KB9X

No it isn't appropriate. There are telephone poles near my house that
if they were to fall will destroy my house. My neighbors TREES could
do the same. Yet most people do not see these as significant hazards.
They are used to seeing them so do not think of them as hazards.

Of course. People are used to things like Power poles and even think
nothing of hurtling at each other in automobiles carrying liquids that
are almost explosively flammable. In no way does that make either
actually "safe".

They are not quite so used to radio towers however. People have a
fear of the unknown, especially in thies days of safe rooms in houses,
and burglar alarms in gated communities.

And in these days of safety taken to stupid extremes, and housing
developments that won't allow you to have a clothesline in your back
yard, I'm not about to go complaining about that one little restriction
on a potential tower.

- 73 de Mike KB3EIA -

PRB-1 and CC&R's
 

On Mar 25, 7:03�pm, Mike Coslo wrote:
"Dee Flint" wrote :

"Steve Bonine" wrote in message
..

And all the logic in the world won't help if the local building
official insists on using the worst-case scenario or local laws
demand it. Frankly, if I was the local building official, I would use
the worst-case scenario. The primary responsibility of a building
inspector is public safety, and invoking the worst-case scenario
seems appropriate in this case.

No it isn't appropriate. *There are telephone poles near my house that
if they were to fall will destroy my house. *My neighbors TREES could
do the same. *Yet most people do not see these as significant hazards.
*They are used to seeing them so do not think of them as hazards.

It's not just familiarity, though. Buildings and utilitity poles
are usually subject to detailed codes regarding their
installation and maintenance. Those codes are based on
extensive experience about what works and what doesn't.

A radio tower is more of a custom installation and requires
special attention.

I agree that using the worst-case fall-circle rule for a
properly-installed radio tower is usually more restrictive
than is needed.

There are situations where the worst-case scenario
applies, IMHO: Field Day and similar temporary installations.
In those cases, where a tower, mast, pole or antenna may fall should
always be considered. Putting a Field Day station
at the base of a temporary tower may look idyllic but is not
a safe practice.

Of course. People are used to things like Power poles and even think
nothing of hurtling at each other in automobiles carrying liquids that
are almost explosively flammable. In no way does that make either
actually "safe".

There's safety and then there's the *perception* of safety.
Driving/riding in autos is one of the most dangerous things
most people do routinely, based on the death and injury
rates.

They are not quite so used to radio towers however. People have a
fear of the unknown, especially in thies days of safe rooms in houses,
and burglar alarms in gated communities.

There's also the Gladys Kravitz effect.

And in these days of safety taken to stupid extremes, and housing
developments that won't allow you to have a clothesline in your back
yard, I'm not about to go complaining about that one little restriction
on a potential tower.

IMHO, that's how restrictions get a foothold.

First it's some little rule that doesn't really seem to make much
difference, even though it's grounded more in
fear than in good engineering.

For example, as Dee points out, the utility poles could fall over and
cause extensive damage, but they're not restricted the way towers are.

Then there's a little expansion of the rule. Maybe it's the fall
circle plus ten percent. Or twenty five percent.

A little here, a little there, and pretty soon you need a property a
couple of hundred feet in every direction to put up a fifty foot
tower.

This may sound absurd, but I'm old enough to remember a
time when, if someone suggested a no-antennas restriction
on houses, they'd have been laughed at because practically
everyone wanted to watch TV, and to do that required a
decent outdoor antenna. Then cable came along and now
they're SOP.

---

btw, even the professionals mess up at times:



http://www.damninteresting.com/?p=500#more-500

http://www.pbs.org/wgbh/buildingbig/.../citicorp.html

http://en.wikipedia.org/wiki/Citigroup_Center

73 de Jim, N2EY

PRB-1 and CC&R's
 

PRB-1 and CC&R's
 

On Mar 26, 9:14�pm, Mike Coslo wrote:
wrote roups.com:

On Mar 25, 7:03?pm, Mike Coslo wrote:
I agree that using the worst-case fall-circle rule for a
properly-installed radio tower is usually more restrictive
than is needed.

There are situations where the worst-case scenario
applies, IMHO: Field Day and similar temporary installations.
In those cases, where a tower, mast, pole or antenna may fall should
always be considered. Putting a Field Day station
at the base of a temporary tower may look idyllic but is not
a safe practice.

Very true.

All too common, as well.

Of course. People are used to things like Power poles and even think
nothing of hurtling at each other in automobiles carrying liquids
that are almost explosively flammable. In no way does that make
either actually "safe".

There's safety and then there's the *perception* of safety.
Driving/riding in autos is one of the most dangerous things
most people do routinely, based on the death and injury
rates.

Surely. I can't explain the contradictions, but I suppose that those who
practice those contradictions don't give it a second thought.

People tend to be more afraid of the unknown. Cars are known.

Another one
along the same lines is that people fear for their health from a 60 Hz HV
line several hundred feet from their house, but doin't have a problem
with sticking their head in the near field of a cell phone and talking
for hours a day like that.

I think a better example is to compare apples to apples:

Some people fear the effects of power-line fields, but not the
fields from their house wiring and appliances - even though the
latter may be much stronger because they're so much closer.

Some people fear the effects of being near cellphone towers,
yet not the effects of using a cellphone whose fields are
stronger because they're closer. Opposition to cell towers has
caused the cellphone folks to install lots of small cells rather
than a few big ones, and to use disguise antennas - including
some that look like trees.

Both are cases of ignorance of such basics as the inverse
square law.

This is not to say that RF and power-line fields have no health
effects at all, just that the real risk factors are often
misunderstood.

*They are not quite so used to radio towers however. People have a
fear of the unknown, especially in thies days of safe rooms in
houses, and burglar alarms in gated communities.

There's also the Gladys Kravitz effect.

Hehe, very true.

ABNER!

*And in these days of safety taken to stupid extremes, and housing
developments that won't allow you to have a clothesline in your back
yard, I'm not about to go complaining about that one little
restriction on a potential tower.

IMHO, that's how restrictions get a foothold.

First it's some little rule that doesn't really seem to make much
difference, even though it's grounded more in
fear than in good engineering.

For example, as Dee points out, the utility poles could fall over and
cause extensive damage, but they're not restricted the way towers are.

* * * * They not only can, but they do! We see that one all the time.

SO it's familiar....

Then there's a little expansion of the rule. Maybe it's the fall
circle plus ten percent. Or twenty five percent.

A little here, a little there, and pretty soon you need a property a
couple of hundred feet in every direction to put up a fifty foot
tower.

* * * * That's a mighty slippery slope there Jim! 8^)

If it happens, it must be possible.

* * * * If I go into a zoning meeting trying to get a waiver to the
"restriction" in my neighborhood so that I could put up a tower larger
than allowed, I wouldn't get too far with terms such as "very unlikely"
and typical failure mode" They are going to "worst case" me in a big way.

Tell it to Citicorp.

And I'm not so sure that if I was a zoning officer that I wouldn't do the
same. The question I would ask: Is it physically impossible for the tower
would fall straight over at the base?

Solution: Windmill tower.

If you can get expert evidence that
it is impossible, I might consider it, if not, I will advise you to be
glad that you are living in a modern village development that allows
towers, but you will have to be satisfied with a tower within the
prescribed limits.

What if you had a contractor set a utility pole for use as a tower?

73 de Jim, N2EY