Tom Rauch wrote:
>> Here's where I'm unclear. Let's say, in addition to the 10
>> lb load at
>> the top, you put a 10 lb load in the middle of the tripod.
>>
>> What do you see on the scales?>>
> Steve,
>
> Getting our arms around a complex issue like this may be
> difficult without a drawing or experiment.
>
> I think the important point is the guyline converts what
> would be large amounts of tension on some legs and
> compression on others to MUCH less compression and greatly
> reduces if not eliminates leg tension.
>
> Think of a self-support as a guyed tower with guylines
> folded in so far they are integrated into the vertical
> members of the tower. Now imagine you move the guys outwards
> to anchor points some distance from the base when guys are
> added.
>
> The only possible danger might be allowing some area near
> the middle of the tower to kick out from direct wind force
> and forces transmitted down through the structure from the
> top, BUT the forces transmitted down through the tower would
> be less with guylines than without them.
>
> The only exception I can think of would be if you really
> seriously overbuild the guylines to the point that the
> static tension increases the load to make some lower area of
> the tower try to kick out. The solution there would be to
> reduce tension or add another set of lines.
>
> I think the only problem is not knowing where to attach the
> guys or what size they should be for optimum rating. I don't
> think there will be very many cases where the wind load
> rating will decrease.
>
> Imagine tramming a large antenna up on a slender mast. How
> many people on this reflector would devote a week and 394 kB
> of text to warning people that back-staying the mast will
> make it more prone to fail as the antenna is trammed up,
> because it was never designed to have a backstay? There we
> have a very slender flexible column, and don't think twice
> about countering the side force caused by the tram line
> tension. Naturally any fool could bend the mast or decrease
> the load survival by using excessive back-guy tension....but
> we all pretty much know (I hope) the back stay is a good
> safety idea.
>
> If I had a self-support tower near a power line, I'd back
> guy or safety guy it with a loose but stout line if it was
> self supporting. The real worry is always common sense and
> using funky materials, that's why the general population
> should stay away from power lines. We tend to use rope and
> wire and flimsy antennas, and tend to NOT take precautions.
>
> 73 Tom
Tom,
I agree with all that, and I think everyone who has been
bewildered by the Don't Guy mantra does too.
Still, I'm confused by the base moment in Jims calcs and
would like to get to the bottom of it.
If I understand him correctly, putting some side force
on the middle of my tripod will cause unequal scale
readings, and I don't understand why.
Steve K8LX
_______________________________________________
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Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
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