[TowerTalk] Pipe for guy anchor

[john at kk9a.com]

I beams should be easy to obtain in most larger cities. If the top is cut on
an angle you should be able to connect a turnbuckle directly to the center
web without have to weld a bracket. K5IU, who designed the Rotating Tower
System, apparently did a presentation on elevated tower anchors. I am not
sure if it exists on the interweb but below is a summary of it written by
W7XU:
GL, John KK9A


The following information was from a talk K5IU (a mechanical
engineer and owner of Rotating Tower Systems) gave at (I
believe) the New Orleans DX convention a few years back:

For posts 7-8 ft above ground:

Installation         Width and Ht.      Length
  Small                  2 ft             5 ft
   Med                   3                9
   Big                   4               10

The above dimensions are for the concrete bunker.  The 
post sits in the middle of the bunker.  The top of the
bunker is 1 ft below ground level.  (Yes, that's right,
almost 6 yards of concrete per anchor for a large
installation).

Post size:
  Round post, with guys attaching at 7-8 ft above ground
Installation         Post diameter         Wall thickness
  Small              5" or larger           0.25" or more
   Med               7" or larger           0.38" or more
   Big               9" or larger           0.50" or more


  Wide flange I-beams, with guys at 7-8 ft above ground
Installation    Wide flange I-beam size, A36 steel
  Small          W 6x12 (6" X 4" - 12 lbs/ft)
   Med           W 8x15 (8" X 4" - 15 lbs/ft)
   Big           W 10x33 (10" X 8" - 33 lbs/ft)

What is a medium or big installation?  I have a rotating 
Rohn 25 tower approximately 135 ft high.  It has eight
17-el 2 meter antennas on it, stacked one above the
other from 30 to 135 ft.  The windload of each antenna
is 2.7 sq. ft., plus phasing lines, etc.  That qualifies
as a medium size installation (per K5IU).

I have another rotating tower, 140 ft high.  Rohn 55.
It's designed to hold a 10 ft dia. dish, a 6 ft. dia.
dish, a 4 ft dia. dish, 8 long boom (~22 ft) yagis on 432, 
4 long boom (~28 ft) yagis on 222, and a couple of
vertical beams for 2m FM and 440 FM.  That is a big
installation.

I have elevated guy posts for both of the above
towers, and followed K5IU's guidelines for the 
concrete bunkers.  I also did some reading on my
own and discussed it with a friend who is a civil
engineer -- it takes a lot of concrete and steel to
make proper elevated guys.  A friend of mine skimped
when he put up what is probably a small system (a
tribander and 2m beam on 70 ft of Rohn 25) and now
his posts are pulled out of plumb.

Hope that gives you some ideas.

-- Arliss W7XU




Rick Harrington N0VT wrote:

My thanks to all who took the time to reply.  I have a much better grasp 
now on what I should (and in some cases, shouldn't) do. I want to use an 
I-beam but the final choice will likely be determined by availability, 
and it's good to know I have options.

73, Rick N0VT