[TowerTalk] 30 foot Rohn 25G calculations

[Gedas]

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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