I've been at the top of my 100' 45G when the wind became so strong I
could no longer work (probably 30-40 MPH) 40 MPH will bounce you
against the tower and difficult to breathe with the wind 90 degrees to
face on. There was definitely no slack on the downwind side, nor was
there any sense of movement. Certainly the tension on the downwind side
is reduced a bit, but it's a long way from being slack. Whether EHS, or
Phillystran the mechanics should prevent the downwind side from going
slack. My experience with the array
http://www.rogerhalstead.com/ham_files/Tower29.htm Makes it difficult to
accept the 15 to 18" deflection. Maybe with a full size 40m Yagi, or
20m long john
With a telescope (lee side of the house, out of the wind) on a day too
windy to climb the tower, I could barely detect movement of the tower
top with the big array up there.
NOTE: scope and tripod weigh over 140#. I need to get something
lighter. A 77 year old back and Arthritis means that scope and tripod
have set in the shop for quite a few years. <:-(.
73, Roger (K8RI)
On 9/24/2017 Sunday 1:25 PM, Grant Saviers wrote:
My reference for noting that guys go slack is the K7NV FEA tower
study. While Kurt doesn't note the stress in the downwind guys the
lean of the tower at the top is pretty convincing to me that they
slack. For 100' tower the top moves 15 to 18" downwind for embedded
base and as much as 54" a for pier pin base. While the wind loads in
the study are high, nothing fails in these models.
For big commercial towers with very heavy guys/ft I have no opinion.
http://k7nv.com/notebook/towerstudy/towerstudy1.html
Grant KZ1W
On 9/23/2017 22:59 PM, Roger (K8RI) on TT wrote:
It depends on the wire (size, length, composition, and the tension. I
used to regularly climb a 200' commercial tower that had 1" wire rope
for guys. there was an 18" tall, guy attachment point (don't remember
the height) Those guys would ring like a tuning fork when struck with
with a metal tool. it was way above 440
Hz. That kind of vibration will unscrew a lot of hardware, but not
with that kind of tension. The tower was a very solid 2' on a side in
20' sections, down onto an elevated pier pin base. The elevated base
was a good 6' on a side. The pier pin was about 7' to 8' above
ground. I have no idea as to how deep the concrete went.
Turnbuckles on 1" guys are BIG!
73, Roger (K8RI)
On 9/22/2017 Friday 8:04 PM, Steve Maki wrote:
On 9/22/2017 19:36 PM, Grant Saviers wrote:
At the specified torque values for structural bolts, the fastener
is far less likely to loosen. That isn't the static load in a
turnbuckle which is exposed to many of the conditions that cause
common fasteners to loosen.
You would think so. But guy wires (and turnbuckles) seem to be under
a different dynamic situation than nuts and bolts in a motor for
example. Vibrations are relatively slow, and tension never nears
zero in a system with proper pre-tension. I think.
-Steve K8LX
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Roger (K8RI)
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