wrote in message
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On Mar 21, 10:33�am, Michael Coslo wrote:
wrote:
On Mar 19, 2:00?pm, "KC4UAI" wrote:
On Mar 17, 9:43 am, wrote:


[snip]

One of the most fortunate bits of luck I had was that although I was
about 5 years away from becoming a Ham when we bought it, the
Neighborhood isn't antenna restricted, with the exception that if you
put up a tower, it has to be far away enough from the neighbors that it
won't fall on their house - seems reasonable to me! ;^)

Depends on the size of the lot. On a lot that's , say, 100
feet wide, you can't put up a tower more than 50 feet high
and have its "fall circle" not go over the property line.


Yet is that actually the correct way to calculate it? That assumes that the
tower will break at the base and fall over from the base. This is not the
common failure mode (or so I've been told). From one of the experts who was
speaking to a city council meeting around here, the towers either twist like
a corkscrew or bend over somewhere between the middle and top. The
"corkscrew" is supposedly the most common failure mode as that is the way
the towers are designed to react if wind loads are exceeded. However in
neither case is there a "fall circle".

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.

Dee, N8UZE

"Dee Flint" wrote ...
wrote ...

Depends on the size of the lot. On a lot that's , say, 100
feet wide, you can't put up a tower more than 50 feet high
and have its "fall circle" not go over the property line.

Yet is that actually the correct way to calculate it? That assumes that
the tower will break at the base and fall over from the base. This is not
the common failure mode (or so I've been told). From one of the experts
who was speaking to a city council meeting around here, the towers either
twist like a corkscrew or bend over somewhere between the middle and top.
The "corkscrew" is supposedly the most common failure mode as that is the
way the towers are designed to react if wind loads are exceeded. However
in neither case is there a "fall circle".

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.

The structure hight as a radius is the "worst-case" limit of
damage. Insurance underwriters, country commissioners,
et.al. likely don't want to expose themselves to the liability
of setting a more risky limit. Our anecdotal history of typical
tower failures may not seem as compelling to people with
actuarial risk at stake.

"Richard Crowley" wrote in message
...
"Dee Flint" wrote ...

[snip]

The structure hight as a radius is the "worst-case" limit of
damage. Insurance underwriters, country commissioners,
et.al. likely don't want to expose themselves to the liability
of setting a more risky limit. Our anecdotal history of typical
tower failures may not seem as compelling to people with
actuarial risk at stake.

Actually shouldn't there be some actuarial data on this? When it comes to
damage, they'd be the most likely to have solid data. I noticed that no one
addressing the council had bothered to get such data either way on this
subject.

At this point, it's just idle curiosity as our ordinance got changed to 75
feet (up from 50) and there was no "fall circle" type of language included.

Dee, N8UZE

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

"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