In a message dated 4/9/2011 12:01:09 P.M. Pacific Daylight Time,
towertalk-request@contesting.com writes:
> New to TowerTalk.....name is Mike, W7PIM and I would very much
appreciate any and all constructive input into my feasibility research.
I have read over much of the archives regarding the things I want to
accomplish and now I need all of you tower/antenna guys out there to rip
into this challenge. Overall objective: Modify my current HDX-555
(555), to hold and rotate
2 or 3 large yagis. (ie: 2 el. on 40, 2 X 6 el on 20, homebrew
antennas) I have not listed any loading or weight numbers here yet
because I am dealing in concepts at the moment. Those details will come
in the detailed math analysis and design to follow.
Howdy --
Okay. Concept - the HDX-555 will not take any of the modifications
you're talking about reliably. Wasatch County is a 70 MPH windspeed zone which
the tower will handle with small to medium antennas - not 2-3 large yagis.
> Objective #1:
Design and construct a bottom section that would raise the tower an
additional 20 ft. Plan would be to use the current winch and lift cable
to raise the current 555 to it's normal height and then use a separate
winch and lift cable to then lift the entire 555 the additional 20 feet
inside the new tower section.
> Objective #2: Design and
construct a tower rotating system that will mount on top of a very heavy
duty pedestal tower or large post section about 3 ft. tall and then
secure the entire assembly from objective #1 to the top of the 3 ft.
section.
I've seen this done but it'll take some clever engineering and
fabrication.
> This brings me to Objective #3: Design and construct
guy rings for the 555 that are custom fitted for each section and would
allow the entire tower to be rotated. Now, before I stir up all the
naysayers out there, let me tell you why I want to do this.
Too late. You cannot guy the 555. Guy rings are generally pretty brute
(see lots of poundage). Between the additional weight of the guy rings and
the added tension on the guys (lots more compression on the tower lifting
cables), all of a sudden the capacity of the 555 will be negative numbers.
> Getting to
old to climb tall towers, and want to homebrew antennas. Need to move
them on and off and up and down tower. This would give me the best of
all worlds for what I need. Resources: Very supportive wife, 10
acres of land, son with MS ME, another son with MS EE, a son-in-law
with ME, 2 brother-in-laws that are certified ASME+++++ welders and a
machinist in the family. Have access to extensive Finite Element
Analysis support, a can do attitude and lots of experience at doing
things that most people won't tackle. Have also reviewed K7NV's
outstanding paper on "Guyed Tower Behavior".
Glad to see you have the engineering resources and have done some of
your homework.
Just off the top of my head, I figure it'll cost $10-20K to do what
you're proposing. Why not put up a real tower that will accommodate what you
want to do and then pay a professional climber when you need him? $10-20K
will go a long way in that direction.
I'm not a big fan of homebrewing towers. I've seen some real nifty
ones but they had major bucks tied up in them - not counting the construction
or engineering.
The guy that mentioned the Hazer has the best idea if done properly,
even though I don't like the idea of loosening guy wires to raise and lower
the Hazer.
Cheers,
Steve K7LXC
TOWER TECH -
Professional tower services for hams
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