[TowerTalk] : Nube rebar question

[Roger (K8RI) on TT]

On 12/17/2014 11:49 AM, Kelly Taylor wrote:

The pier pin base allows the tower to "pivot and rotate."  It basically 
removes the torsion forces and bending moment from the tower although 
they are not a problem worth considering in "MOST" ham installations as 
the towers are more than capable of handling the torque.  Big antennas 
and stacks are something else.

Among the advantages of the pier pin are no worries about water freezing 
in the base, Stress is reduced on the tower joints and bolt holes, easy 
to take the tower down, or swap towers.  Star guying is recommended though.

They do require a little more care up to the first set of permanent 
guys.  However all towers should be subjected to the same care.

73

Roger  (K8RI)

> The roof mounting plate, as described, seems to solve a few issues relative
> to embedding tower sections or base tubes in concrete ‹ helps prevent water
> intrusion into the base, permits re-use of base for other towers, etc. ‹ but
> leaves one issue unresolved. At least, it does if I'm reading the
> description correctly.
>
> The OP mentioned he uses threaded rod to keep the base from twisting, but
> wouldn't you WANT some twisting at the base? Isn't that the rationale behind
> using a pier pin instead of any kind of fixed base? In other words,
> torsional forces reaching the base of the tower result in nothing more than
> slight rotation around the pin rather than becoming a source of fatigue
> failure in the legs?
>
> Did I miss something in 20 years of towertalking?
>
> 73, kelly
> ve4xt
>
>
> On 12/17/14 10:28 AM, "K7LXC--- via TowerTalk" <towertalk at contesting.com>
> wrote:
>
>>>   Can anyone provide a good reason not use a roof mount for
>> theseinstallations?   I would be very interested.
>>   
>>      Additional cost? Hams are a well known bunch of  cheapskates.
>>   
>> Cheers,
>> Steve     K7LXC
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-- 

73

Roger (K8RI)


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