Hi, Rich!
> Howdy, saw your posting on the TowerTalk Reflector,
18/7/97 0305, regarding
> the Rohn Tilt Towers. I'm planning to install the Rohn
FK25 68 footer this
> fall, so I'm doing some homework now.
>
> I gather that you have a FK25 68 already up and inplace.
Wonder what kinds
> of antenna(s), mast (length and diameter), and rotor that
you are using.
> Do you have a fairly good idea of the weight of each
component?
Well, the foldover isn't back up yet. I still have many
hours to go cleaning all of the sections, painting with
paint designed for repainting galvanized metal ("Tower
Paint", I know Rohn sells it ($$$) but I'm looking for a
less expensive source). A good suggestion from WQ9E is to
paint the insides of each section, running a wire through
each vertical tube and then pouring in some paint, then
pulling through a cloth/foam/whatever "wad" to effectively
smear the paint inside the tubular sections. This won't
apply if you are putting up a new tower, nacherly. But do
paint the plated bolts!
Antennas topside will vary, but it will probably carry the
TET 43sp (4 el tribander, 20' boom) that was purchased with
the tower, at least initially, as it is in excellent
condition and works (the previous owner maintained honor
roll status with it). If it performs according to the
book, it will be very competitive with current antennas on
a 20 foot boom.
I will probably use an HD73 rotor, as it also came with the
tower. I will probably look for the largest capacity rotor
that will fit within a #25 section, as the HD73 did require
repairs twice over a 12 year span. Then again, rotor
repair with a foldover is more a nuisance than a chore, and
I read somewheres on the reflector that somebody out west
is still providing parts for Alliance rotors.
My only change from the original setup is to skip the
original 20 foot 1.9 inch O.D. heavy wall well pipe that
was used as a mast (the rotor was mounted about 15 ft down
from the top) with a much shorter 2 inch dia. 1/4 inch wall
aluminum mast, with as little mast as possible sticking out
of the top section. I'm gaining considerable weight
savings here. A TB3 thrust bearing will be placed in there
somewheres as well. I do need to check to see that a 2
inch OD mast will fit through the tube in my 25AG2 top
section, though.
>
> I have been following the Reflector discussion on the
Tilt towers and
> wonder if you have any suggestions/precautions that I
should
> consider/investigate.
>
Force 12 sez the 420/240 presents 8 sq. ft and weighs 65
lbs. Rohn sez a double guyed FK2568 will handle 11.7 sq ft
in a 20 PSF area, and 6.2 sq. ft. in a 30 PSF area in my
older catalog. If things aren't too windy at your QTH, you
will be within the specs. Remember, that keeping within
published specs might come in real handy should an
insurance claim ever need to be filed!
I'd also try to stay within the 100 lb total topside load
weight to keep stresses on the hinge reasonable when you
are folding the thing over, again, per Rohn's notes. Maybe
consider the aluminum mast idea that I plan to use, save
some pounds for a hefty rotor. Just don't stick the
antenna on top of an aluminum mast that is 10 feet above
the tower apex,
unless you can find a mast rated at a heck of a lot more
than the 40000 psi that 2 inch diameter, quarter inch wall
6061 will handle before breaking!
> I plan to go with the Force12 420/240 (2 el on 40M, 4 el
on 20M on 30 foot
> boom) for starters. The top set of guys on the Rohn will
be Phillystran
> while steel will be used for the hinge guys.
>
73! - Mark
----------------------------------------
Mark Shaum K9TR
mashaum@fcg.net
Central Illinois Grid EN50
---------------------------------------
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