[TowerTalk] vertical mast calculations
Jim White, K4OJ
k4oj at tampabay.rr.com
Sun Mar 23 19:27:42 EST 2003
I have sorta been following this thread, it seems to me that using HF
tapered element components and boom sized tubing with adapters you
should be able to construct a vertical that does not have to be fat at
the top...these 3" all the way up jobs are huge!
At least I hope so - I have been saving pieces and parts from HF 20 and
40 meter elements thinking they would be useful in a four square array
for 80 some day... I had envisioned one or two section of Rohn 6 or
similar lightweight tower as the bottom and then 2" tubing dropping down
to the 40 meter Telrex elements to get up to around 66 feet...
The only part of the project that seems hard is insulating the tower
from ground - I refuse to pay for the turned fiberglass pieces that
several market for Rohn legs, it seems like a foldover base which mounts
to a product like "plastic lumber" which in turn is mounted to a buried
base should do the trick.
My question is how good/poor a conductor of RF is the recycled pop
bottle "plastic lumber" is... it is available in "4 X 4" size and I
would think I could carriage/machine bolt a tiltover base to it and that
in turn would be bolted to a small concrete base...
The goal is to have the elements completely free standing - no mid-point
guying, etc... I may have the opportunity to put something like this up
in the neighbors field adjacent to the QTH but will have to go with
buried ground system since the cows that graze there can not get
entwined in elevated radials.
SO - Towertalkians am I dreaming or is this feasible - it sure seems
like the tubing portion of the elements should be fine - if they can
withstand being horizontal continuously they certainly should be able,
if mounted with even heavier tubing and then tower below them to stand
Thanks in advance,
Remember: 34 days until the Florida QSO Party, check it out at:
Dave Hachadorian wrote:
> On Sun, 23 Mar 2003 09:15:24 -0800 "Jim Lux" <jimlux at earthlink.net>
>>I just ran across the following QEX article on the ARRL web site:
>>It gives all the necessary design equations, etc. for unguyed
>>The article references an excel spreadsheet available as well.
>>(http://www.arrl.org/qexfiles/) look for Travanty.zip
> Thanks a lot for that tip. The spreadsheet is very easy
> to use, and imported fine into Quattro Pro. It includes mast
> bending moment calculations. It was fun to crank the tower
> up and down, and vary the windspeed.
> The main assumption though, is that the failure points are at
> either the tower base, or the mast at the thrust bearing. If
> there is an unusually weak link in the tower, other than those
> two, the spreadsheet is not valid.
> Dave Hachadorian, K6LL
> Yuma, AZ
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
> TowerTalk mailing list
> TowerTalk at contesting.com
More information about the TowerTalk