In a message dated 97-10-24 03:52:56 EDT, k9rz@probe.net (Bill Jackson)
writes:
<< If I were to install a 20 ft. mast with the rotor mounted
between the 45AG4 top section and the standard section below it, the
seperation would more likely be 9-10 ft. My first question is, can a 20
ft. long 1/4" wall carbon steel CD mast be SAFELY installed through the top
of the tower using a 12 ft. WB0W gin pole?
Barely. I have the WB0W ginpole myself but outfitted it with a HD 15
foot piece of aluminum ginpole mast. I use it strictly for lifting big masts
since it's WAY too heavy for stacking tower sections.
Another technique you can use (prescribed by N4SI - whatever happened to
him anyway?) is to raise the mast vertically (choked just above the balance
point) and then turn the mast over 180 degrees once it's at the top of the
tower. While the weight will be above the balance point, it's held by the
ginpole and actually turns out to be a pretty straightforward way of doing
it.
>>Option 2 would be to use a 10 ft. length of this mast with the rotor
mounted 3 ft. inside of the tower, with a 7 ft. spacing between the
antennas. Am I asking for trouble here due to the lack of Z bracing on the
top 3 ft. of the top section and the amount of bending moment that may be
ecountered in this area of the top section? The top guy bracket is
attached at the bottom of the first full set of Z braces from the top,
which is just below where the rotor shelf would normally mount.
This is within the specs of the tower and IMO would not overstress the
tower system. But the closer the rotator shelf is to the guywire attachment
point the better. The torsional wind load is transferred to the rotator and
then to the tower legs so if the load is then transferred to the guy wires,
your tower doesn't hardly get torqued at all.
>> Option 3 would be to scrap the stack idea, sell the KT34XA and go with a
Force 12 C4XL mounted just above the top of the tower using the 10 ft.
mast. >>
Naw. Go with what you've got.
73, Steve K7LXC
TOWER TECH -- professional tower supplies and services for amateurs
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