[TowerTalk] mast

[Mark .]

<< From: K7LXC@aol.com

In a message dated 05/01/2000 2:57:06 PM Pacific Daylight Time,
kn9t@webtv.net writes:

>Need some help here on a source and type of
>  3 inch mast 21 or 24 foot long to hang a kt34xa
>  and 2 ele 40 with12 foot seperation.
>  Is the steel pipe from my local industrial supply
>  2.875 OD  .276 wall  sched. 80 beefy enough ?

...snip... The pipe you mentioned is around 35kpsi but with that much wall 
it'll probably survive....snip >>>

Hold on there, Steve. This sounds like common 2.5" water pipe, not 
structural tubing. The "schedule #" and the dimensions give it away.
Unless the factory has marked the material and you are sure, this type of 
pipe is usually wrought iron or wrought steel and it's yield strength can 
vary anywhere from 23,000 to 32,000 psi according to data I could find In 
Machinery's handbook.
To be conservative, I don't think you can count on more than 25,000 psi 
yield strength from common water pipe.
This application has one antenna at least 13 feet above the tower (12' 
separation above first antenna), quite a moment arm indeed!
I wouldn't trust this application to a material that I didn't know the 
properties of, for sure.
Don't forget to include a safety fator, too: Re-run MARC with 25,000 psi 
allowable or less and see if it's OK.
I'm working up a spreadsheet for this. If you give me the projected areas 
for those antennas, I'll run the numbers here, too.

--...MARK_N1LO...--


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