Al-
I am in the same boat-- I can handle stresses and strains, and know the
difference between "tensile strength" when the reference is cable or steel
bar, but the cautions about where to hook up puzzle me. How you NOT hook,
directly or indirectly to a Z-brace is still an unknown. The vertical load
has to go somewhere.
(the question is a little academic, because I'm 81 and my wife wont let me
climb anymore)
Bill--W4BSG
----- Original Message -----
From: "Alfred Frugoli" <ke1fo@arrl.net>
To: "Bill Aycock" <baycock@hughes.net>
Cc: "Richard Elizondo" <relizondo@ionoscom.com>; <towertalk@contesting.com>
Sent: Monday, November 24, 2008 2:11 PM
Subject: Re: [TowerTalk] Climbing and working on Rohn 25g/45g towers -
> What is difficult in this entire conversation for me is that I'm not an
> engineer - I'm trained as a manager and I'm an amateur radio operator by
> choice. You can talk about specs and theory all you want. What I need to
> know is where do I connect my fall arrest lanyard. It seems to me that no
> matter where you connect to on xxG tower you're connecting to a cross
> brace. If I connect directly on the cross brace, obviously I'm on the
> cross
> brace. If I connect on the tubular vertical member and I fall, the force
> still rests on the z bracing where it is welded to the vertical tube.
>
> So, how does one safely connect their fall arrest lanyard on xxG tower?
> Must it be connected to multiple legs to be safe?
>
> A pictoral tutorial of this information would be helpful. My knot book
> with
> diagrams, pictures and drawings is invaluable to me - is there such a
> thing
> for tower rigging and climbing?
>
> 73 de Al, KE1FO
>
> -----
> Visit my amateur radio contesting blog at ke1fo.wordpress.com.
>
>
> On Mon, Nov 24, 2008 at 2:55 PM, Bill Aycock <baycock@hughes.net> wrote:
>
>> Richard-
>> I still consider that your post contains statements that are essentially
>> meaningless, because they relate to loads in terms that do not directly
>> relate without more explanation and definition.
>>
>> My career was as a Rocket motor designer, and , of necessity, included a
>> working knowledge of material properties and how they relate to applied
>> loads. My problem with your statements is that there is no meaning to the
>> phrase "shear strength" without knowing how the loads are applied. The
>> primary loads on a guyed tower are compressive and tensile; on an unguyed
>> tower, bending becomes more important. In a tower, the applied loads are
>> compression and tension, with shear being induced, not directly applied.
>> The
>> resistance to shear in a complex structure is different for different
>> parts
>> of the structure, and can not be determined if the point of force is not
>> given, with respect to the geometry.
>>
>> When a climber hangs on a tower, the total load is his weight, but the
>> stresses are distributed differently if he is in line with a 'point' or a
>> 'face'; to determine factor of safety, one must know where he is. This is
>> a
>> fact.
>>
>> At one point in your answer you claim that you have just stated the
>> facts.
>> To be a useful fact, the statements you made need more clarification.
>> Where
>> did the shear strength statement come from, and did it originally
>> come with a definition?
>>
>> Bill-W4BSG
>>
>> ----- Original Message -----
>> From: "Richard Elizondo" <relizondo@ionoscom.com>
>> To: "Bill Aycock" <baycock@hughes.net>; <towertalk@contesting.com>
>> Sent: Monday, November 24, 2008 11:24 AM
>> Subject: Re: [TowerTalk] Climbing and working on Rohn 25g/45g towers -
>>
>>
>> > The strength of the section is made up of its parts. If the section
>> > fails
>> > to
>> > provide a 5000lbs anchor point, in no way will any of the welds, legs
>> > or
>> > lattice, provide it either.
>> >
>> > I am not stating the 25g tower is worthless. I actually quite fond of
>> this
>> > tower and own several gin poles that are made of 25g, 45g and 55g
>> > sections.
>> >
>> > What I have stated are just the facts. Like it or not, take it to
>> > heart,
>> > or
>> > with a grain of salt.
>> >
>> > Ever wondered why Rohn used to make comments about climbers being less
>> > than
>> > 250lbs in their field erection manuals ? (Hmmmm ...250lbs ...10-1
>> > safety
>> > factor for positioning.... I must not know what I am talking about.)
>> >
>> > Seriously though however, I am open to discussion on what you see as
>> > erroneous in my post, since it is the same lecture given in all
>> > comtrain,
>> > belltech, and Radian fall protection classes.
>> >
>> > Richard
>> >
>> > ----- Original Message -----
>> > From: "Bill Aycock" <baycock@hughes.net>
>> > To: "Richard Elizondo" <relizondo@ionoscom.com>;
>> > <towertalk@contesting.com>
>> > Sent: Monday, November 24, 2008 8:31 AM
>> > Subject: Re: [TowerTalk] Climbing and working on Rohn 25g/45g towers -
>> >
>> >
>> >> This Whole post contains a major flaw that makes the real part
>> >> irrelevant.
>> >> The statement about the strength of 25g is worthless, because the
>> >> shear
>> >> strength is not define with respect to direction and method of
>> >> loading,
>> >> and
>> >> is not related to the type of load applied by a falling body.
>> >> If the loading is cleared up, the rest might be germane.
>> >> Bill-W4BSG
>> >>
>> >> .contesting.com/mailman/listinfo/towertalk
>>
>> _______________________________________________
>>
>>
>>
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