[TowerTalk] 30 foot Rohn 25G calculations

TexasRF--- via TowerTalk towertalk at contesting.com
Fri Feb 13 10:25:36 EST 2015


Joe, the over tightened leg bolts you saw were very likely someone's  
attempt to recover from an egged out leg hole situation. It won't work; only  
tight fitting joint bolts will keep the joints properly joined.
 
The cure for preventing egged bolt holes is proper tightness in the first  
place as John and others have reported. 
 
To be fair, I have also seen Rohn 25G, 45G and 55G tower sections with  
egged out bolt holes, caused by the same fault, under tightened joint  bolts.
 
I have recovered a few of these sections by reaming the hole back to round  
and using an oversized tight fitting bolt. I doubt that Rohn would approve 
this  but a frugal Ham (like myself) would do it anyway.
 
I don't see any reason this "fix" can't be used on an aluminum tower  
section as well. 
 
73,
Gerald K5GW
 
 
 
 
 
In a message dated 2/13/2015 6:21:23 A.M. Pacific Standard Time,  
w4tv at subich.com writes:


I  saw plenty of Heights and Universal towers that were egged out
during my  time on Ohio.  Many of them had the bolts/nuts tightened
to the point  that the legs were somewhat flattened but that did
not prevent "egging  out".  I know one old timer in the Columbus
area who replaced towers  twice within 10 years - both times because
they were so badly egged out  that nobody would climb them to repair
antennas.

Again after what I  saw of those towers, I would not trust one here
in the higher/constant  winds in Florida.  If I had to use a free-
standing tower here, it  would be the biggest sections available
from AN Wireless or a properly  engineered commercial - Rohn SSV,
Pirod (if they're still around), etc. -  tower with bolted flanges.

73,

... Joe,  W4TV


On 2015-02-12 5:09 PM, n8de at thepoint.net wrote:
>  Joe,
>
> The 'egging out' is usually caused by insufficient  tightness in the
> original erection.
> Have had many (over eight)  Universal towers since 1975, and only once
> did that factor into the  situation ... my error is not retightening the
> bolts/nuts AFTER  erection.
>
> Those 'light duty' towers are TV towers in my mind,  and would never use
> one.
>
> 73
> Don
>  N8DE
>
>
> Quoting "Joe Subich, W4TV"  <lists at subich.com>:
>
>>
>> On 2015-02-12 2:00  PM, n8de at thepoint.net wrote:
>>>
>>> A free-standing  Universal aluminum tower composed of 26" tapered,
>>> 22" tapered,  and 18" topper will support ANY common
>>> tribander/vertical/VHF  combo presently being used in ham radio.
>>
>> While that  may be true in Michigan where the wind requirements are not
>>  particularly high (70 MPH rev F, 90 MPH Rev G), that may not be true  in
>> Seminole County, Florida where the building requirements are  for 140
>> MPH (139) wind speed.
>>
>> Note the  force due to wind is *2.5 times higher* at 140 MPH than at
>> 90  MPH.  Directly comparing the allowable antenna in Rohn's  example
>> designs for 90 and 130 MPH indicates the same tower will  support
>> less than half as much antenna 1t 130 MPH as it will  support at 90
>> MPH.
>>
>> Universal Towers does  not even give windload data for 140 MPH on their
>> web site (they  provide spec's at 80, 100 and 110 MPH for the light duty
>> towers  but nothing for the heavy duty models) but given the nearly
>>  constant winds in Seminole County, FL, I would *never* trust one  of
>> their towers as I've seen how badly their bolted connections  "egg
>> out" after only a few years in the much more calm areas of  the Great
>> Lakes region.
>>
>>  73,
>>
>>    ... Joe,  W4TV
>>
>>
>> On 2015-02-12 2:00 PM,  n8de at thepoint.net wrote:
>>> Unless he is intending to put up a  stack of huge monobanders and/or
>>> SteppIR yagis, he doesn't  need the 30" sections.
>>>
>>> A free-standing  Universal aluminum tower composed of 26" tapered, 22"
>>> tapered,  and 18" topper will support ANY common tribander/vertical/VHF
>>>  combo presently being used in ham radio.
>>>
>>> Do  the research ... I have 3 Universal towers up now ... and plan to  
put
>>> up 4 more soon.
>>>
>>>  73
>>> Don
>>>  N8DE
>>>
>>>
>>> Quoting Gedas  <w8bya at mchsi.com>:
>>>
>>>> Brian, I would  not rule out a free standing tower esp since you need 
to
>>>>  stay under 30'.
>>>>
>>>> I have several  self-supporting Universal towers here, each of which
>>>> uses  as their first 3 sections, their 30" HD series sections.   When
>>>> assembling the towers and after getting those first 3  sections up in
>>>> the air, you realize how strong that  structure is.
>>>>
>>>> In your case, since you  mentioned 24', I would use two 30" HD 
sections.
>>>> See if you  can get the top section modified either by Universal or by
>>>>  a local welding/fab place to make it a topper with a collar where  you
>>>> can then use a 2" or 2.5" mast.  My gut tells me  that two 30" HD
>>>> sections with a 4'-5' mast will still be  standing long after your home
>>>> is leveled from some severe  wind storm.
>>>>
>>>> Gedas,  W8BYA
>>>>
>>>> Gallery at  http://w8bya.com
>>>> Light travels faster than  sound....
>>>> This is why some people appear bright until you  hear them speak.
>>>>
>>>> On 2/12/2015 1:03 PM,  Brian Carling wrote:
>>>>> Many thanks  Bud.
>>>>>
>>>>> I will need to review  which version they are using. Yes I had
>>>>> someone  pointing me in the direction of a freestanding tower but  I
>>>>> think I may go to using  guys.
>>>>>
>>>>> It's either that or  trade my tower sections in on a stronger better
>>>>> built  freestanding tower designed for that purpose. I only  need
>>>>> about 24 to 28 feet in height.  Maximum.
>>>>>
>>>>> Best regards - Brian  Carling
>>>>> AF4K Crystals Co.
>>>>> 117  Sterling Pine St.
>>>>> Sanford, FL  32773
>>>>>
>>>>> Tel: +USA  321-262-5471
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>  On Feb 12, 2015, at 12:27 PM, W2RU - Bud Hippisley
>>>>>>  <W2RU at frontiernet.net>  wrote:
>>>>>>
>>>>>>
>>>>>>>  On Feb 12, 2015, at 9:58 10AM, bcarling at cfl.rr.com  wrote:
>>>>>>> I am putting together a permit  application with my city which
>>>>>>> requires  certfication for 139 mph
>>>>>>> for three second  gusts as in TI-222 spec. Also steady 100 or  110
>>>>>>> mph I  think.
>>>>>>> We are making a 30 foot Rohn 25G tower  according to the Rohn
>>>>>>> specification with   4 foot
>>>>>>> cube base of concrete with no  guys.
>>>>>> I?m not sure I understand what you?re hoping  to find.
>>>>>>
>>>>>> My 4-year old  Rohn catalog makes it VERY clear that 30 feet of   
Rohn
>>>>>> 25 can hold only 1.7 sq. ft. of added antenna  when the  environment
>>>>>> is 90 mph (ANSI/EIA-222  Rev. E) and NO ICE.  (For  areas that
>>>>>>  experience icing, Rohn 25 is specified by the  manufacturer at  ZERO
>>>>>> sq. ft. of additional antenna load!)   From  your e-mail address and
>>>>>> the wind speeds  you mention, I?m going to  guess you?re in  Central
>>>>>> Florida, and I daresay a 90-mph Rohn   EIA-222 Rev. E specification
>>>>>> is not going to be  adequate for your   city.
>>>>>>
>>>>>> Nowhere in your  posting do you mention what total antenna,   
rotator,
>>>>>> feedline, etc. wind surface area or wind  load you  anticipate
>>>>>> putting on this  tower.  But my guess is that NO  freestanding  30?
>>>>>> Rohn 25 tower is going to make the  grade.
>>>>>>
>>>>>> Also, you fail  to mention which version of TIA/EIA-222 your city   
is
>>>>>> using.  The latest I?m aware of is Rev. G  ? a substantial  revision
>>>>>> from previous  methods of specifying wind  loading.
>>>>>>
>>>>>> Bud,  W2RU
>>>>>>
>>>>>>
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