Memory-wise I’m not having a good morning.... Thanks to all who gently pointed
out that I DO have Rohn 45G (as I initially thought) but then I got confused as
to the fact that it IS considered free standing below certain heights,
something that I had clearly forgotten long, long ago. That is a good reminder
to me to re-read the manual before commenting on it.
So Jim, back to my original point.... :-)
I have personally guyed my Rohn 45G towers at the 40’ and 80’ levels (and again
at 120’ for the top tower). Even if I was only putting up 40’ of Rohn 45G, I
would STILL have guyed it anyway just for the extra support. Even though the
specs suggest otherwise, I always liked the idea of making equal vertical
spacing of the guys –> 40’ and 80’. If I was putting up 70’ of Rohn 45G, I
would have guyed at 35’ and 70’. I also suggest that you consider using a
pier-pin with flat base plate as this will reduce the torque on the tower-legs
and reduce structural fatigue in violent storms. Of course you can only do
this if you guy the tower and it makes it harder to put on the first set of
guys but I believe that it is a better strategy long term.
I would also suggest doing something that some on this reflector feel is
unnecessary – the use of ice-clips on each pre-form on each guy. I live on a
hilltop in SW CT that gets an average of 6+ ice-storms per year. My qth is
just high enough (810’ asl) to stay below freezing when surrounding areas are
several degrees above 32 F. We also get ice-storms when areas North of us get
snow even though I am at the same temperature as them – I am too close to Long
Island sound (22 miles) for the atmosphere aloft to stay below 32 F when some
of the big Nor’easters develop and draw in the warmer Atlantic ocean air and
moisture which wrap around the storms. The result is freezing rain with temps
even as low as 22 F and sleet with temps even as low as 12 F! This is an issue
for me due to with the local topography and how the storms develop. You may
have similar local wx issues with your terrain which may subject you to more or
less wind/icing.
So anticipating the wind and icing extremes here, I wanted to insure that water
could not work its way into the end of the preforms – then freeze and expand,
and in doing so, possibly loosening the preforms and jeopardizing the guys. So
I used ice-clips which you bang onto the end of each preform on each guy. I
have never had a failure. For me it was cheap “insurance” despite the extra
cost and extra work. Given that you live in Michigan you might want to
seriously consider it.
73
Bob KQ2M
From: Bob Shohet, KQ2M
Sent: Sunday, May 06, 2018 10:11 AM
To: jrquark ; towertalk@contesting.com
Subject: Re: [TowerTalk] Guying a Self supporting Tower Beyond the Height of
Self Support
Agghhh.... My apologies to the reflector. I had a “brain-freeze” on the Rohn
45G. It most definitely IS self-supporting. I remembered the the “G”
incorrectly and I have Rohn 45 towers not Rohn 45 G.
Ignore my point #1 except for the “put it up now and be done with it.”
Points #2 and #3 are still accurate. But I would still follow the
manufacturer’s specs and if they do not talk about guying the free-standing
Rohn 45 G then I would not do it, nor would I exceed their height
recommendations/weight/wind load recommendations.
73
Bob, KQ2M
From: Bob Shohet, KQ2M
Sent: Sunday, May 06, 2018 9:26 AM
To: jrquark ; towertalk@contesting.com
Subject: Re: [TowerTalk] Guying a Self supporting Tower Beyond the Height of
Self Support
One other thing... Rohn 45 G is NOT self-supporting. I assumed that you knew
that by asking about potential guying points even though the subject line of
your post said “Guying a self-supporting tower”.
As a general rule, you should always follow the manufacturer’s instructions
when planning an installation. You didn’t mention whether or not a variance or
building inspection is required by your tower for your proposed tower. If no
variance or inspection is required it will be much easier. If a variance
and/or inspection is required then the inspector and/or p & z may insist on
proof that your installation meets the guidelines of the Rohn specs – another
reason to “do it by the book”.
73
Bob KQ2M
From: Bob Shohet, KQ2M
Sent: Sunday, May 06, 2018 9:19 AM
To: jrquark ; towertalk@contesting.com
Subject: Re: [TowerTalk] Guying a Self supporting Tower Beyond the Height of
Self Support
Hi Jim,
Congratulations on your new tower!
A few comments and suggestions...
I have 2 Rohn 45 G towers – one at 100’ guyed at 30’, 60’ and 90,
and big tower of 130’ guyed at 40’, 80, and 120’ – with star guys at 80’ and
120’
Both towers have one leg ~ 8’ – 10’ lower in the vertical plane than the other
two legs and both towers have one guy anchor substantially closer or farther
away from the tower base than the other two legs. The 130’ tower has one guy
anchor ~ 150’ long from the base vs. the other two guy anchors ~ 95’ away. The
100’ tower has one guy anchor at ~ 70’ from the base, one at 90’ and one at ~
110’ thanks to solid ledge in most places. Highly complex and variable terrain
can make guy anchor placement very challenging – the important things is to
overbuild (rather than underbuild) with larger bases and guy anchor points and
thicker guy wire – this gives additional protection against violent storms and
potential failure – and to equalize guy wire tensions.
1) If you are planning to go to 80’, then guy at 40’ NOW.
The guying at 40’ should support 50’ of Rohn 45 with your planned antenna and
rotator although it is not advisable, and the difference between 40’ and 50’
will not be that significant for antenna performance. Personally, I would put
the tower up at 80’ NOW and guy it and be done with it. THEN put the antenna
and rotator on it later. Taking the antenna and rotator off to add sections
and then putting it back up is a real nuisance.
2) Since you have a significant difference in elevation in one leg of the
tower, I would advise against have the guy points equal distances apart and
then having different horizontal components tension to equalize them. The
distance from the tower to each guy anchor is less important than having equal
tension on them - ideally measured and set with a LOOS tower gauge at ~ 550
lbs for 1/4” EHS guy wire.
3) Take your time and be sure that you are installing everything properly.
73 and GL!
Bob KQ2M
From: jrquark
Sent: Sunday, May 06, 2018 8:54 AM
To: TowerTalk@contesting.com
Subject: [TowerTalk] Guying a Self supporting Tower Beyond the Height of Self
Support
Greetings all, newcomer here.
Never having done this before, I’m seeking input, ideas and suggestions.
I purchased five - 10 ft sections of Rohn 45G, actually eight.
From Rohn’s plans for a self-supporting 45’ tower, I followed the plans and
stacked the tower to 50’, I know, I know, it’s not 45’!
My wife and I bought and constructed a Mosley Pro67 c3 and and bought an Alpha
Spid rotor. All this during the last Michigan winter. We were eager to place
the beam atop the 50’ tower and get on the air after a long absence from ham
radio, and we thought about going up to eighty feet later. But we changed our
minds and decided to go higher and wait a bit longer..
Where do I guy it? Eighty foot Rohn plans suggest 35’ and 65’. But a tower
climber and other hams that all had many towers under-their-belt, had other
suggestions, i.e., 45’, 75’ and 80', etc. My location is not level ground.
The three proposed anchor locations are ~90’ horizontally from the tower. One
location is elevated about 8’ , the others are ~5’ and ~10’ below the level of
the tower base.
I can get the horizontal components tensions worked out so the total horizontal
load at each guying height is balanced, even though the vertical component, on
the three tower legs will not be the same, harrumph.
Nuf said. Any suggestions.
Thank you for your time reading this.
Jim Forsman - K7BIE
Linda “Poo” Forsman - K7POO
P.S. We are on a forested 1.5 acre lot in Southwest Michigan.
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