Hi all!
Well, I'm thrashing. I'm less than a year into my first tower and I'm
trying to figure out how I can expand on it with the least expense and
the most safety. I'm hoping I can bounce some ideas around this reflector
for comment - TIA!
Here's what I have now (I LOVE it!)
Trylon 72' self supporting tower (Thanks Steve!) rated load 45 ft^2
(I live in a 70-mph county).
T2X 8' mounted down from the top - thrust bearing at top.
16' 2" 1/4" wall 4130 mast leaving about 8' sticking out of the top
Rated yield strength from manufacturer = 105,000 psi
F12 C31XR 1' above top (lots of wasted space above that!)
I would like to add beams for 40, 17, and 12 and I've been looking at
F12's beams (since I've been so happy with the 31XR):
12/17:
WARC2/2 load 3.1 ft^2 about 20#
40 (about 1dB gain difference & some bandwidth between them):
Magnum340 load 6 ft^2 about 60#
EF240X load 4.1 ft^2 about 40#
EF240 load 4.1 ft^2 about 35#
Two of my options involve some sort of mast coupler. What is the
skinny on these? Are they safe? What do they do to the overall
yield strength of the overall mast?
What about interaction on stacking? What should the distance between
the C31XR, 40M, and WARC beams be?
So, to look behind doors 1, 2, and 3:
Option 1: Moderate cost, pretty safe?
Buy 5-10 feet more 4130 coupled to existing mast.
WARC2/2 on top of new mast 12-16' above C31XR.
40M beam on TIC ring rotor at ~50' level (~23' below C31XR).
Worst case calculation for 70MPH wind rating (longest
mast, no 40M beam):
WARC2/2 17' up at 3.1 ft^2
C31XR 1' up at 10.5 ft^2
17' 2" mast 8.5' up (midpoint) at 1.9 ft^2
1' 3" coupling (size guess) 8' up at .2 ft^2
Required yield strength = 37,500 psi
Best case calculation for 70MPH wind rating (shorter
mast, enough seperation?):
WARC2/2 13' up at 3.1 ft^2
C31XR 1' up at 10.5 ft^2
13' 2" mast 6' up (midpoint) at 1.5 ft^2
1' 3" coupling (size guess) 8' up at .2 ft^2
Required yield strength = 26,951 psi
Option 2: Lowest cost, safe at all?
Buy 13-20 feet more 4130 coupled to existing mast.
40M beam halfway to the top above C31XR.
WARC2/2 on top of new mast >10' above 40M.
Worst case calculation for 70MPH wind rating (longest
mast, biggest 40M beam, too much to rotate?):
WARC2/2 27' up at 3.1 ft^2
Magnum 340 14' up at 6 ft^2
C31XR 1' up at 10.5 ft^2
27' 2" mast 14' up (midpoint) at 3 ft^2
1' 3" coupling (guess) 8' up at .2 ft^2
Required yield strength = 95,100 psi - not much margin
Better case calculation (shorter mast, smallest 40M beam -
enough seperation?):
WARC2/2 20' up at 3.1 ft^2
EF240 10' up at 4.1 ft^2
C31XR 1' up at 10.5 ft^2
20' 2" mast 10' up (midpoint) at 2.3 ft^2
1' 3" coupling (guess) 8' up at .2 ft^2
Required yield strength = 60,100 psi
Option 3: Highest cost, safest?
2nd tower with 40M and WARC beams on top.
So, what do you think?
Thanks es 73!
-Brian n8wrl
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