Hi Jari,
I agree that, as a goal, you should always follow the manufacturers
instructions. However, in some installations that may not be possible
due to topography and other reasons.
Both my towers, 100' and 130' of Rohn 45, went up in 1998. The 100' is
guyed with 1/4" EHS @ 30', 60' and 90'.
The 130' tower is guyed with 1/4" EHS @ 40', 80, and 120'.
Both towers use pier pins and a base plate that can swivel to release
tension.
The Rohn 100' has one short Guy @ 62' from the tower base with two
others > 75'.
The Rohn 130' has one long Guy @ 170' from the tower base with two
others ~ 96'.
The Rohn 100' has guys spaced 110 degrees, 120 and 130 degrees.
The Rohn 130' has guys spaced 110 degrees, 120 and 130 degrees.
The towers have survived direct hits from 3 tornadoes (EF0 and EF1), 2
Hurricanes - one with winds gusting > 110 mph and numerous T-storms,
Macrobursts and Microbursts with winds approaching 120 mph, as well as
countless ice storms and some with with heavy winds.
The Rohn 100' short guy @ 62' from the tower base prevents rotation via
a side mount at lower heights. It would have been ideal to have the guy
80' from the base.
The Rohn 130' guys @ 96' prevent rotation from a side mount at 80' - it
would have been best to have the guys 100' from the base. The third guy
is 170' from the base - far longer than ideal.
Both towers have been up continuously for the past 23 years without any
structural issues becoming evident.
I hope that this information is helpful to you.
73
Bob, KQ2M
On 2021-07-27 05:31, Keith Dutson wrote:
To be safe, do not rely on opinions. Get your advice from either the
manufacturer or a registered professional.
73 Keith NM5G
On Tuesday, July 27, 2021, 02:49:25 AM CDT, Jari Jussila
<jari.jussila@oh2bu.pp.fi> wrote:
Hi ...
I'm sure these topics have been discussed earlier, but could not find
any thread ..... Sri ...
We are at our club erecting two towers. A rotating steel tower being 31
m high and a aluminium telescope mast 18+18 m = 32 meters.
A) How critical is the rule that guy wires should be "exactly" 120
degrees apart?
A professional guide says, that the anchor point can be 50 mm from that
120 degree (119,9-120,1 degree) but some say, that a maximum of two
degrees is OK. That meaning 118-122 degree.
What's the tower community advise?
B) The steel tower height is 31 m - it's a rotating tower - but the
upper bearing is at 23 m ( leaving 8 meters for the antennas) and the
lower bearing at 11 meters.
Whats the advise of anchor point distance? Some say, that the 60 %
(distance for the tower) should be calculating from the total height
(31 x 0,6 = 18,6 meters).
Some say, it should be calculating from the upper bearing (23 m x 0,6
=
12.8 m)
Whats your opinion?
Jari, OH2BU
For OH3AC Club Station
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|