Although just a nit and too large a guy wire would put undue stress/pull on
the legs, the highest stress point is probably going to be the base.
although the lower guys are more of a straight out pull. I'd taken some of
the old American Steel (two bolt) towers down that had 1/4 steel guys
properly tensioned. The bottom three sections took a jack to get them
apart. The sections had actually "belled" out between the bolts or at least
above the bottom of the open section. This effectively swaged the sections
together. Over the years I took down three 90 foot tall American Steel
towers like that with 1/4" steel guys. All three required the use of a jack
to get them apart. As the cross section of the tower leg was no longer
straight this should have substantially reduced the strength in the vertical
plane. As memory serves all three legs in each case were pretty much equal,
but that means with one person with enough equipment to hit 200# total was
probably seriously overloading the tower.
Every thing was done well, except the strength of the tower had not been
taken into consideration or the consequences of using over size guy wire.
Guyed at three points that were close to equally spaced and the top set
within a foot of the top, each section weighs 30# for a total of 270# a bit
of trig will show those guys were putting substantial downward force on
those towers. Use the cosine of the angle to horizontal at the tower.If the
top guys are at 45 then cos(45)* 670# tension = 352# downward force for each
line or 1055# downward force *just* for the top set of guys. Add to that
the tension and weight of the guys for all three levels plus the weight of
the tower and it has to be close to 2000#.
How many of us would intentionally put up a 90 foot tall TV tower and then
put a one ton weight on top of it? How many of us would then add another
200# consisting of ourselves and equipment to the tower by climbing it?
That was a long time ago and I'm not taking any more American Steel towers
Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com (Use return address from home page)
> Is there a correct pull ?
> Easy answer to your question.
> Go by whatever Rohn recommends for the guy wire. If you use 3/16 inch
> you should have approximately 390 lbs of force on it. If you use 1/4
> EHS, use approximately 670 lbs. If you use 5/16 use around 1100 lbs.
> Just use
> whatever the book recommends for guy wire and you should be fine.
> It is possible to use too heavy a guy wire and the 10% figure would
> be trying to pull the tower apart. An extreme example would be using
> on Rohn 25 and using 1100 pounds of pull on it...not too smart!
> Bill K4XS/KH7XS
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