[TowerTalk] turnbuckle safety wires

Sun Sep 24 18:40:52 EDT 2017

While I haven't built a tower FEA model and run my own Finite Element 
Analysis to check Kurt's work, I've been through his work several times 
and can't find fault.  Not surprising, since he is much more qualified 
than I am as an ME.  I did have a good discussion with him at the 
Visalia convention this year about his modeling assumptions and inputs 
and that confirmed IMO that the modeling is well done.  It is worth 
reading to understand why your experience at 30mph is different than the 
math at max wind (I'll go with the math).

I remember looking at the tall guyed broadcast towers east of I95 south 
of the Mass Pike when a hurricane was warming up.  The lean was 
noticeable, maybe 10's of feet at the top.  Actually, there is DATA in 
the NAB Engineers Handbook

https://books.google.com/books?id=K9N1TVhf82YC&pg=PA1642&lpg=PA1642&dq=broadcast+tower+wind+sway&source=bl&ots=RtqdbP9_tu&sig=7FFsqw2hXl5vVgMYpM-qk5-TWig&hl=en&sa=X&ved=0ahUKEwjoj_eK7b7WAhXLr1QKHVBJBsMQ6AEIOTAD#v=onepage&q=broadcast%20tower%20wind%20sway&f=false 

shows a table 6.8.3 for 1100' tower sway at 50 mph fastest mile of 
0.57deg.  100mph = 4x the force so maybe 2 degrees or 38' at the top.

Grant KZ1W

On 9/24/2017 14:15 PM, Roger (K8RI) on TT wrote:
> 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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