I have a real problem with this. I have asked for a description of the way a
force is applied to the tower, and how the tower section is mounted, to show
how this "strength" is defined. So far I have no luck.
Tossing phrases like "Shear Strength" around without knowing what they mean
is silly.
Bill--W4BSG
----- Original Message -----
From: "Bill Coleman" <aa4lr@arrl.net>
To: "Richard Elizondo" <relizondo@ionoscom.com>
Cc: <towertalk@contesting.com>
Sent: Thursday, December 04, 2008 7:07 AM
Subject: Re: [TowerTalk] Climbing and working on Rohn 25g/45g towers -
>
> On Nov 23, 2008, at 11:43 PM, Richard Elizondo wrote:
>
>> Here is the shocking sad truth:
>>
>> Rohn 25g section shearing strength - 2500lbs (this is the strength
>> of the
>> entire section, all three legs and lattice, not just that one leg
>> you may be
>> attaching to.
>>
>> So a Rohn 25g section could fail if a climber falls and the lanyard
>> shock
>> pack does not activate, or the climber is using a lanyard without a
>> shock
>> pack.
>>
>> Sadly enough the Rohn 45g section is not that much stronger.
>
> However, in a fall arrest situation, it is unlikely that all of the
> arrest force occurs in the shear direction. 25G has considerably more
> vertical support strength. On a 200 foot 25G tower, the static load on
> the base likely exceeds 2500 lbs to start.
>
>> Solutions for the Climber:
>>
>> First and foremost - Never attach to the Z lattice of these towers
>> for any
>> reason.
>
> If a single weld fails, then the Z bracing will deform -- that
> deformation will absorb some of the fall energy. The remaining energy
> will be directed at the remaining upper and lower welds. It seems
> unlikely that a 6 foot fall would create so much energy as to undo
> every weld on a section.
>
> It does seem seriously unwise to attach to the top or bottom "flat"
> part of the bracing. There, a single weld failure would likely allow
> the fall arrest lanyard to detach from the tower entirely.
>
> 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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>
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>
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