[TowerTalk] 30 foot Rohn 25G calculations

Thu Feb 12 17:09:57 EST 2015

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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