On 5/6/12 11:58 AM, Wayne Willenberg wrote:
> I really need some input on the design of my first tower.
> As I have previously mentioned on this Reflector, I want to put up a 100 ft
> guyed tower on my 5 acre lot that will support 20 sq ft of antenna,
> rotator, etc. To get a building permit, the tower has to be designed to
> meet the requirements of TIA/EIA-222 for a maximum wind gust of 130MPH.
> I have now located a PE who is licensed in my home state and has
> substantial experience in the design of ham towers. I have also located a
> professional installer who will supervise and participate in the entire
> installation (in other words, I will not be doing any of the work).
> Here is the dilemma the designer has presented to me. (The following are
> not real examples, but are just used to illustrate the point.) I could use
> Rohn 25 with 18 total guys or I could use Rohn 65 with 9 guys. In the
> first case, the tower sections would cost less than in the second case, but
> there would be more labor in installing 19 guys (and the guys would cost
> more) than 9 guys. Also, the amount of concrete in the base and the guy
> anchors would be different.
> There must be a way to determine the most cost-effective selection of type
> of tower and number of guys.
short of actually calculating it out, not really..
However, fewer parts is better. 9 guys & 65 is a whole lot simpler.
(and easier to stand on for climbing, and easier to fit things like
rotators in). If you're going up high enough to need 3 guy levels on
65, you're not just turning that TV antenna.
If you're dragging something up the tower, half the number of guys will
be good. Your installer will like you more.
For a guyed tower, the amount of concrete in the base won't be hugely
different. It's mostly there to keep the base from sinking or skidding
sideways (as opposed to a free-standing tower, where it's to keep the
tower from falling over)
If you use the big screw in auger anchors (where the truck with the
hydraulics comes out to drive them), you don't need concrete in the
anchors, and the cost will be about the same..
(the wind load isn't going to be hugely different, whether it is spread
over 6 guys or 3)
I would venture to say that nobody ever says "gosh, I wish I installed a
lighter weight tower with more guys"
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