I think you're getting confused. The analysis shows that if the base is fixed
or doesn't allow the tower to lean over, then there will be either a twisting
moment induced into the tower, which will cause it to fail somewhere around the
midpoint but not at the base, or if the tower can not lean over, then a lot of
downward compression force (the downwind side) may make a tower leg become
overloaded and buckle, again not at the bottom but somewhere up from the
bottom. So, very few failures of the bottom itself, but unless the bottom
design is helping, like a tapered base (allows the tower to twist and to lean
over), then those opposing forces will manifest themselves somewhere else up
the tower. Make sense?
The rotating tower rotator may allow for the twist problem but may not be good
for the leaning over problem. We have both to contend with. Phil KB9CRY
-------------- Original message --------------
> in addition... while thinking about the conclusion of K7NV's tower stress
> analysis I wondered
> why I have never heard of a tower failing due to the BASE rupture or anything
> related to the base!
> If indeed the worse case stress is at the base with the lowest safety factor
> typically being caused
> by bending then why are there no failures at this point?! [Or are there and I
> have just not heard of them?]
>
> All the tower failures I have heard of were due to twisting and not related
> to
> the base failing. Thus is it
> indeed possible, although the math says it is the weakest link, that the base
> has a higher safety factor
> (i.e. something was left out of the calculation - not an unusual circumstance
> and by no means a
> derogatory comment on K7NV's excellent analysis)?
>
> Has anyone heard of a tower failing AT THE BASE (when installed properly of
> course)?
>
> Also - does anyone have the RTS rotating tower system rotor and can you say
> if
> there is any "pivot"
> capability due to the rotor section? If it allows pivoting of even 1/2 degree
> this would I believe be the
> equivalent of a tapered point base section would it not?
>
> Gary
> K9RX
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
> Weather
> Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
> and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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