[TowerTalk] unguyed heights for Rohn 65 etc.?

[Pete Smith]

A little bit of mathematics may be understatement.  K7NV did a nice piece 
of computer analysis on guyed towers (see http://k7nv.com/notebook/ ) which 
at least illustrates the thought process and some of the non-intuitive 
things that can happen.

It strikes me that there's a reason why self-supporting tower designs all 
taper from the bottom -- presumably a lot of the steel in an unguyed 
straight tower is overkill near the top and insufficient at the bottom.  I 
also haven't seen any discussion in this thread about the size of the 
concrete base that would be required, or the way the tower would be 
anchored to the concrete.

73, Pete N4ZR

  At 12:54 AM 1/14/2005, Jan Erik Holm wrote:

>Dont you guys ever do calculations on things like this?
>A little bit of mathematics will figure all this out,
>also I´m pritty sure there would be computer software
>that can do stress calculations on towers depending
>on how much load you put on them etc etc.
>Used to do this when I was in the university, however
>it was 30 years ago and darn it if I can remember how
>to any more, should be able to study up on it I guess.
>However these days I guess you do it in computers and
>not by hand and brain.
>
>73 Jim SM2EKM
>-------------------
>
>RICHARD BOYD wrote:
>>Okay, it looks, then, as if Rohn 65 would do the job at 50' but wouldn't 
>>be enough at 60' -- unguyed.  I would guess that Rohn 80 would have a 
>>little more capability, being huskier.
>>Even putting one guy set on the tower should greatly increase its 
>>capability -- I'll have to think about the aesthetic and footprint 
>>tradeoffs versus the other options.
>>73 - Rich, Ke3Q
>>
>>----- Original Message ----- From: "Joe Subich, K4IK" <k4ik at subich.com>
>>To: "'RICHARD BOYD'" <ke3q at msn.com>; <towertalk at contesting.com>
>>Sent: Thursday, January 13, 2005 10:59 PM
>>Subject: RE: [TowerTalk] unguyed heights for Rohn 65 etc.?
>>
>>
>>>
>>>>Anyone have an idea (or facts) how high I could go unguyed
>>>>with Rohn 65, assuming a single 48' boom monobander for 20,
>>>>or 15, or 10 (plus appropriate rotator, and I'll have the
>>>>yagi right above the tower, shortest mast possible within
>>>>reason)?
>>>
>>>The Rohn Commercial Catalog (11993) gives the following
>>>allowable antenna areas for Rohn 65 at 80 MPH (Prince Georges
>>>Co. is 75 MPH zone):
>>>
>>>
>>>Ht.      no ice    1/2" ice
>>>
>>>50'       19.7       19.1
>>>60'        9.4        4.1
>>>
>>>Note 3:  Designs assume two 7/8" lines on each tower face.
>>>         (nb: 7/8" line is .0875 sq. ft. per lineal foot)
>>>
>>>
>>>>Okay, let me toss out another possibility:  Rohn 80 (I know
>>>>it comes in various sub-models, some 40" face, some 44" face
>>>>and there may be other differences, but assume the basic or
>>>>the typical one).
>>>
>>>No chart in my book for Rohn 80 free standing.  "Each tower
>>>is individually engineered to handle a particular job."
>>>
>>>Rohn 80 is 41" center-to-center on the legs however the legs
>>>vary from 2" to 3" in standard (schedule 40?) and X-STR
>>>(schedule 80?).  Rohn 80 has both standard (zig-zag) and
>>>cross braced sections.
>>>
>>>73,
>>>
>>>   ... Joe, K4IK
>
>_______________________________________________
>
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>
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