I agree with Roger in that the angle of the guys at each tier should be
equal -- if possible. In my case, the ground was so steep that it wasn't
possible to do this precisely for all three levels without separate anchors.
However, I equalized the angles of the top guys and managed to get the
angles of the middle and bottom guys pretty close. These are the computed
guy angles:
Flat East South Northwest
Ground Guy Guy Guy
Top 44.08 44.02 44.06 44.18
Middle 55.60 57.51 56.18 53.50
Bottom 70.27 75.23 71.79 64.88
The East guy is uphill, the Northwest guy is downhill and the South guy is
almost flat (slightly uphill.) As you can see, the delta for the middle guys
is 2 degrees or less, and the delta for the bottom guys is 5 degrees or
less. I felt this was close enough to forego separate guy anchors.
I also agree with Dave that you need to get the tower vertical before
finalizing the tension. I plumbed and set the tension after attaching each
set of permanent guys. I felt it was important to do this in order to make
the incomplete tower safe for climbing and raising heavy sections. I think
this also makes tensioning each subsequent tier easier, because the sections
below are already plumb and can be used for visual reference.
For each section, I adjusted the guys to roughly plumb the portion of the
tower affected by those guys, with the tension at about 200 lbs. I did this
by sighting up along the three faces of the tower. It's pretty easy to see
when the tower is out of plumb. I also checked the bottom section with a
long level. Could have used a plumb line dropped from the top, but that
wasn't necessary. After getting the tower plumb, I went from anchor to
anchor, slowly increasing the tension, turning each turnbuckle the same
amount. After each round of tensioning, I re-checked the plumb and made any
necessary adjustmemnts. It took three or four trips around the anchors, plus
running in to check the tower plumb, before reaching final tension. After
installing all three sets of permanent guys, I re-checked the plumb at all
three levels (it was very close), made any necessary adjustments, then did a
final check with a transit level about 100 feet from the tower (or maybe it
was 200 feet.) As I recall, the tower was within an inch of plumb from top
to bottom without further adjustment.
Since my guys are Phillystran, I set the tension to 15% of breaking
strength. Within a few days the tension dropped back to 10% of breaking
strength, which is where I left it. The relaxation was symmetrical, so I
didn't have to make any further tension adjustments.
Photos are at www.wc1m.com under Big Tower Project.
73, Dick WC1M
> -----Original Message-----
> From: Roger (K8RI) [mailto:K8RI-on-TowerTalk@tm.net]
> Sent: Saturday, January 16, 2010 3:04 AM
> To: Tower and HF antenna construction topics.
> Subject: Re: [TowerTalk] FW: Guy article in CQ
>
>
>
> K1TTT wrote:
> > Ah, but if you have asymmetric guys, which ones do you put the gauge on?
> > Here are some things to consider.
> >
> If they are all the same angle they are *basically* symmetrical for both
> vertical and horizontal tension. The tension should be the same75.23
> regardless of length.
> > The key is that when the tower is vertical the horizontal force from all
> the
> > guy wires HAS to be equal.
> If you are referring to one tier, that is true, but again if they are
> the same angle the tension in both the vertical and horizontal axis will
> be the same for each guy regardless of length.
> > If it weren't then the tower would be moving!
> > So the objectives are 2 things... first, to have the tower vertical.
> > Second, not to exceed manufacturer specs on tower or guy wire forces.
> >
> > If all the guy wires are the same it is obvious that you only have to
> > measure the tension on one set of guy wires and the others have to be
the
> > same if the tower is vertical.
> Not necessarily. You can get more than a 20% differential between guys
> for tension on a 45G. 25G is less susceptible to this than the 45G as
> the 25G is far more flexible.
> I've found it necessary to go back and fourth between guys with the
> tension gage to get them correct. If you take up too much on one side
> you can get a rather strange looking tower when looking up the side.
> The legs will not be straight.
> > But if the guy wires are at different angles
> > to the tower the ones that are closer to the tower will have higher
tension
> >
> The guys will have the tension you put on them which is based on the
> working strength of the guy. If the guy is rated at 6000# then it should
> have 600# tension. The important thing is to keep the angles the same,
> not the lengths when the terrain is uneven or sloping. The lengths can
> vary quite a bit, but within reason as you have to be aware of creating
> low frequency resonances.
> > than the ones farther out(it goes as the cosine of the angle between the
> guy
> > and the tower, or the sine of the angle from the ground to the guy
wire).
> > So as you pull a guy wire farther out from the tower the tension in it
has
> > to decrease to keep the tower vertical.
> >
> > Now the question is, which one do you measure?
> All of them.
> Particularly on a 25G which is far more flexible than the 45G you can
> make it look like a pretzel if the guys are not properly tensioned in
> careful order. You slowly approach the desired tension by carefully
> going back and fourth between the guys a bit at a time while checking to
> make sure the legs of the tower are straight. A 100' 25 G guyed at 3
> levels can end up with the mid tier of guys as much as 3 or 4 inches out
> of plumb (I've seen them worse than that) with the rest of the tower if
> care is not given to the guy tensioning. Unfortunately a flexible tower
> like the 25G will allow you to pull all guys for a particular tier tight
> (to the proper tension) by actually moving the tier out of plumb when
> tightening one guy line. Those in particular require approaching the
> proper tension slowly and in small steps. Actually you can carefully set
> it equal and THEN using the turn buckles increase the tension on each
> one by a specific number of turns such as 2 or 3. This works IF the
> tower was straight and the tensions were equal to start. Once a tower
> gets out of plumb it can be a real bear to get straight and it becomes
> quite easy to put a permanent set in the tower. Once the tower takes a
> set it'll never be the same.
> > Personally I would recommend
> > measuring the tension on the one that is anchored closest to the tower
> since
> > this one would have the highest tension.
> It should have the same tension as all the other guys on that tier. All
> guys of the same size/strength should have the same tension regardless
> of length.
> > This will result in lower than
> > recommended tensions in the other guy wires which will make them
look/feel
> > loose.
> No it won't and don't go by looks such as the catenary. the tension gage
> is your guide as is the tower remaining straight.
> > If the farther out ones are much farther out than the others there
> > may be problems with movement in the wind because it will have more
slack
> to
> > be taken up.
> No, it shouldn't have more slack if the tension is properly set. It will
> have a definitely deeper catenary though which is entirely different. A
> deeper catenary does not necessarily mean the guy does not have enough
> tension. For two guys of the same length and angle it would indicate
> tension, but a longer guy will have a noticeably deeper catenary for the
> same tension.
> > This is one of the reasons that rohn specifies limits on guy
> > locations, if you go outside their limits you should have the design
> > evaluated by an engineer...
> The distance from the base of the tower is to confirm where the guy
> would be on level ground when all have the same angle.
> > there may be other options, like changing the
> > guy wire type,
> Guys should be of the same type and at the same angle for any given
> tier. If the ground slopes up they will be shorter than shown in the
> catalog and if it slopes downward they will be longer.
> > elevated anchors,
> Elevated anchors are not a good idea unless you have no option. I had to
> clear a driveway and an elevated anchor, back guyed was the only option
> to keep the angle correct.
> > using 4 anchors instead of 3,
> With 4 point guying the angles still should be the same.
> > or other
> > configurations to equalize the anchoring.
> >
> There are only two things that will equalize the anchoring. The guys at
> the same angle for the tier and *each* guy tensioned with a gage unless
> you bend the tower.
>
> 73
>
> Roger (K8RI)
>
> > David Robbins K1TTT
> > e-mail: mailto:k1ttt@arrl.net
> > web: http://www.k1ttt.net
> > AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> >
> >
> >
> >> -----Original Message-----
> >> From: Roger (K8RI) [mailto:K8RI-on-TowerTalk@tm.net]
> >> Sent: Friday, January 15, 2010 22:46
> >> To: Tower and HF antenna construction topics.
> >> Cc: 'N1MM'
> >> Subject: Re: [TowerTalk] FW: Guy article in CQ
> >>
> >>
> >>
> >> Rex Lint wrote:
> >>
> >>> Tom, et. al.,
> >>>
> >>> A couple of field days ago we put up a tower with one of the anchors
> >>> reeeeaaaalll far away: they guys on this side were very long.
> >>>
> >>> When we tightened all the guys, the long ones were "looser" then the
> >>>
> >> others
> >>
> >> I think someone was confusing the catenary (sag) with tension.
> >>
> >>> - they sagged like crazy. But, we cranked away with the come-along,
and
> >>> finally the tower BENT OVER at the lower guy point.
> >>>
> >>>
> >>>
> >> That is because too much tension was put on the longer guys. With the
> >> same tension the longer guys will have much greater sag in this case.
> >>
> >>> Out take-away was, "Keep all sets of guys symmetric."
> >>>
> >>>
> >>>
> >> Although it is a good idea to keep guys symetrical this was not a case
> >> of asymmetrical guys, but some one assuming the longer guys weren't
> >> tight enough. In cases like this it should have been obvious that even
> >> with the extra sag the effort to use the come along would have
indicated
> >> the guys were under plenty of tension. When ever pulling like that use
> >> a tension gage.
> >>
> >> 73
> >>
> >> Roger (K8RI)
> >>
> >> _______________________________________________
> >>
> >>
> >>
> >> _______________________________________________
> >> TowerTalk mailing list
> >> TowerTalk@contesting.com
> >> http://lists.contesting.com/mailman/listinfo/towertalk
> >>
> >
> >
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
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> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
> >
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