self supporting TV towers

[Dan.Strassberg]

Ever see the video of the WBZ (AM) towers in Hull during a nor'easter
before they were reguyed a decade or more ago? In those days, the 'BZ
towers were guyed at only two levels, which was customary at one time
for guyed towers of that height. They were intended to flex in high
winds and boy, did they ever! Since the towers are ~500' high, the
video (someone must have the URL--I don't) gives you a chance to
estimate the excursion of the tower tops. If somebody told me it was
greater than 10', I wouldn't argue. Today, those same towers are guyed
at four levels. A friend who is an engineer, albeit not a structural
engineer, insists that the old two-level guying was safer than the
four-level guying, which is the current practice. He cites the old,
~750' KFI tower, which was felled five or so years ago when struck by
a small airplane. Many years earlier, before it was re-guyed at four
levels, that tower, which was then guyed at only two levels, survived
a hit by another small plane. Difficult to imagine those slender
structures being designed to bow and bend significantly, but I assume
that the structural engineers who designed them knew what they were
doing.

-----
Dan Strassberg (dan.strassberg@att.net)
eFax 1-707-215-6367

----- Original Message ----- 
From: "Jim Hall" <aerie.ma@comcast.net>
To: <boston-radio-interest@bostonradio.org>
Sent: Monday, September 28, 2009 8:30 AM
Subject: RE: self supporting TV towers


>I remember the Sunday Globe had a multi-page color insert about the
>new
> Channel 7 tower when it first went on the air. I wish I had saved
> it. I
> remember in one hurricane we had, Channel 7 put a camera underneath
> the
> tower and showed how much it was swaying in the breeze. I was amazed
> that a
> self-supporting tower could move that much without collapsing.
>
> -----Original Message-----
> From: boston-radio-interest-bounces@tsornin.BostonRadio.org
> [mailto:boston-radio-interest-bounces@tsornin.BostonRadio.org] On
> Behalf Of
> Ron Bello
> Sent: Monday, September 28, 2009 1:48 AM
> To: Kevin Vahey
> Cc: boston-radio-interest@bostonradio.org
> Subject: Re: self supporting TV towers
>
> Although both 4 and 5 moved their transmitters to Needham / Newton
> in 1957,
> it took until 1964 for WNAC 7.  I can remember watching the welders
> from a
> small hill just on the other side of 128 with a telescope.
>
> The lack / cost of available land was probably a major factor in the
> choice
> of a
> self-supporting tower.  That area was well built out by the early
> 1960s.
>
>
>
> On Mon, Sep 28, 2009 at 1:11 AM, Kevin Vahey <kvahey@comcast.net>
> wrote:
>
>> Towers in Paris don't have hurricaines to worry about :)
>>
>> Seriously I don't pretend to understand the plus and minus of tower
>> construction. Obviously WNAC-TV designed the tower well as it is
>> still
>> standing.
>>
>> 7 was forced to move from Malden when both 5 and 4 moved to
>> Needham-Newton. Just was curious in the overall thinking 50 years
>> ago.
>>
>