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Re: [TowerTalk] Tower Base Round or Square?

To: "Joe Subich, W4TV" <lists@subich.com>
Subject: Re: [TowerTalk] Tower Base Round or Square?
From: Pete Smith <n4zr@contesting.com>
Reply-to: n4zr@contesting.com
Date: Thu, 27 Oct 2011 13:36:11 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Sorry Joe, but Rohn 45G and "pier pin" adds up to a guyed tower to me.

73, Pete N4ZR

The World Contest Station Database, updated daily at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at 
reversebeacon.blogspot.com,
spots at telnet.reversebeacon.net, port 7000 AND now
at arcluster.reversebeacon.net port 7000



On 10/26/2011 7:47 PM, Joe Subich, W4TV wrote:
>
> > Does this apply to a guyed tower?
>
> Our discussion was about towers in general ... there was no mention
> of guyed vs. self-supporting or single pier vs. multiple pier (e.g.,
> Rohn SSV with its wide base).
>
> In any case, looking at the Rohn web catalog will show that CB1G is
> specified for all heights of Rohn 25 - except the tallest at 110 MPH.
> Two guy anchors are used in the three tallest 110 MPH designs and
> those towers are specified for GB2G.  CB1G is a 2' 6" x 4' 0"
> square base ... CB2G is a 3'0" x 4' round base.  The Rohn document
> is quite emphatic that CB1G *must* be square.
>
> The trends are consistent in the 45, and 55 documents as well -
> CB1G may be used for the shortest towers but must be square.  Larger
> round piers are specified for taller towers and those with higher
> wind ratings.  Even the smallest of the 65 towers start with CB2G.
>
> 73,
>
>    ... Joe, W4TV
>
>
> On 10/26/2011 5:21 PM, Pete Smith wrote:
>> Does this apply to a guyed tower?  I can understand big overturning
>> forces in a self-supporter, but most of the forces acting on a guyed
>> tower base are vertical, aren't they?
>>
>> 73, Pete N4ZR
>>
>> The World Contest Station Database, updated daily at 
>> www.conteststations.com
>> The Reverse Beacon Network at http://reversebeacon.net, blog at 
>> reversebeacon.blogspot.com,
>> spots at telnet.reversebeacon.net, port 7000 AND now
>> at arcluster.reversebeacon.net port 7000
>>
>>
>>
>> On 10/26/2011 5:10 PM, Joe Subich, W4TV wrote:
>>> I asked the same question of a well known Professional Engineer a
>>> couple of years ago.  His answer was quite simple and made a lot
>>> of sense ... the round base can be used instead of a square one
>>> if the diameter of the round base is the same as the *diagonal*
>>> measurement of the square base.
>>>
>>> In your case, for a 2' 6" (30") square base the round equivalent
>>> would be 42" diameter *not* 36" as you propose.  The reason has to
>>> due with projected surface area - the area that resists overturning
>>> - not volume (or weight) of the concrete.
>>>
>>> 73,
>>>
>>>       ... Joe, W4TV
>>>
>>>
>>> On 10/26/2011 1:28 PM, Richard Thorne wrote:
>>>> I'm finally getting some dirt work done in the next day or two at 
>>>> my new
>>>> place which will include holes/concrete for my 45g tower.
>>>>
>>>> I plan on using a pier pin install, so does it matter if the base is
>>>> square or round?  The rohn book calls for a 2' 6" square hole 4' deep
>>>> (I'm designing the tower based on 90mhp winds with a height of 120').
>>>> It would be easier to use a 36" auger to dig the hole.  Since I'm 
>>>> going
>>>> with a pier pin I don't see that there would be any twisting 
>>>> moments on
>>>> the concrete base, it would only be there to hold the tower up.  
>>>> But I'm
>>>> not an engineer, hence the question.
>>>>
>>>> Thanks
>>>>
>>>> Rich - N5ZC
>>>>
>>>>
>>>> _______________________________________________
>>>>
>>>>
>>>>
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>>>
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>>>
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>
>
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