[TowerTalk] Maximum Guy Radius

[K1TTT]

The sum of the weight of the guys is not what is important, it is the weight
per foot and how that affects the sag vs tension curve.  For instance if you
have 3/16" guy it takes lots less tension to produce a given amount of sag
than it does for 3/8".  The 10% of rated tension kind of takes this into
account by preloading the heavier, higher rated, wire to a higher tension
which probably brings the sag in the wire back to about the same as a
lighter wire.  By increasing the span of the guy wire you increase the sag
for a given tension, thus allowing more movement for a given tension... So
it might be advisable to increase the preload, or it might not, a real
mechanical engineer would have to evaluate the tradeoffs based on the tower
design.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net
 

> -----Original Message-----
> From: Art [mailto:k6xt at k6xt.com] 
> Sent: Wednesday, September 21, 2011 21:10
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Maximum Guy Radius
> 
> 
> Philly is quite expensive compared to wire, insulators and fittings. 
> Good if its in the budget.
> 
> I didn't quite understand the concern over the weight of guy 
> wires. Take 
> my latest project as an example, since I have no data on your tower. 
> Mine is 150 ft of Rohn 55, rotating with three K0XG rings. 
> Guys a little 
> over 1:1 with the top guy at 42 degs neglecting sag. Bottom 
> guy 17 degs. 
> Top guy 5/16, the rest 1/4. Guy wire weight is perhaps 250 lbs. Rings 
> sum to 450 pounds. What I won't have, since the tower 
> rotates, is the 3 
> inch mast and medium prop pitch I used on my Rohn 45 160 ft 
> tower that 
> survived San Diego county Santa Ana winds for 16 years. About an even 
> trade for the rings. With a 50 ft 5L20M ant at 175 ft and lesser size 
> ants below it.
> 
> Then each guy is stressed to 5-10% of its strength. Each guy, 
> therefore, 
> is under more stress than the entire weight of all guys. Rohn 55 is 
> rated to 400 feet in my 90MPH wind configuration, that is 4,000 lb of 
> tower plus guy stress and weight without anything on top.
> 
> My conclusion is wire guy weight is not exactly 
> inconsequential, they do 
> weigh something, but is a minor effect in the overall tower 
> scheme. One 
> solidly built climber weighs about the same.
> 
> I'd be far more concerned about calculations for what you 
> intend to put 
> on it, how many guy levels are necessary to support that load in your 
> wind loading/icing conditions, what size guys to use, and of 
> course, all 
> that vs the tower specs. It might be really beefy looking tower - but 
> they all have limits.
> 
> 73 Art
> 
> On 9/21/2011 12:50 PM, Jay Kesterson K0GU wrote:
> > On 9/21/2011 11:31 AM, Dorn Hetzel wrote:
> >> This tower is 180 ft in nine 20 foot sections of 46" face 
> angle iron. 1400
> >> lbs a section, 12600 lbs total.
> >>
> >> I was sort of assuming I would have to use something on 
> the order of 3/8 EHS
> >> for this.  Do you
> >> think this is something I could do with phillystran ?
> >>
> >> Regards,
> >>
> >> Dorn
> >> KB4EQ at hetzel.org
> >     If you can afford it you can do it with Phillystran.
> >
> > http://www.phillystran.com/163.htm
> >
> >     I'm not sure this has any relevance on anything but 
> most people I
> > know with tall tower often only have one set of guy anchors. So the
> > lower guys are already at a much reduced angle.
> >
> > 73,  Jay  K0GU
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
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> >
> 
> 
> -- 
> Regards
> Art
> 
> _______________________________________________
> 
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