> 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
>>>
>>>
>>> _______________________________________________
>>>
>>>
>>>
>>> _______________________________________________
>>> TowerTalk mailing list
>>> TowerTalk@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>
>> _______________________________________________
>>
>>
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