[TowerTalk] FW: Guy article in CQ

Sat Jan 16 04:17:08 PST 2010

> 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 same
> regardless of length.

Look at the message this started from, it was an obviously asymmetric
situation so that is what I was addressing.

> > 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.

The same works for each tier of guys.

> >  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.

My premise is that once you have the tower vertical the side forces are the
same.  I'll give you a +/- something on larger towers, but probably not much
more than the measurement error in a typical clamp on guage.

> >  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.

No they won't.  in the case under discussion they tried to put the same
tension on the longer set of guys and obviously pulled the tower out of
plumb... so you can't just apply a tension gauge and get the tower plumb.
If they were properly tensioning the short guys the longer one would have a
lower tension, and any attempt to properly tension it would over stress the
other 2.

> > 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.

Not necessary, as you state below.

> 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. 

see, if you tighten one guy to the proper tension without watching the
movement of the tower you will get it wrong.  The 1st step is to get the
tower plumb, THEN bring up the tension equally.  If you go around bringing
up the tension first you will get it wrong since once you tension the first
guy the others will be at the same tension (assuming they are symmetric) and
you won't be able to make the tower vertical.  Its even worse if they are
asymmetric, if you adjust the one with the biggest angle first you will
never get the tower vertical without overtensioning the others.

> 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.

That's why you get it vertical first.

> >   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.

Only if they are symmetric, again this case was an obvious case of

> >  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.

The tower remaining straight is your guide, the gauge is to let you know
when to stop increasing the tension.

> >   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.

In the obvious asymmetric case we are discussing that is what they observed
that started the problem.

> >  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.

But obviously this wasn't possible in the case under discussion.

> > 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.

But obviously this wasn't possible in the case under discussion.

> > 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.

These were just listed as possible methods to avoid a big asymmetric
arrangement, and was prefaced with 'evaluated by an engineer' since they are
obviously not covered in manufacturer catalogs.

> >  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.

So you tension with a gauge 'unless' you bend the tower, what do you do

> 73
> Roger (K8RI)
> > David Robbins K1TTT
> > e-mail: mailto:k1ttt at 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 at 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)
> >>
> >> _______________________________________________
> >>
> >>
> >>
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> >>
> >
> >
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