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Re: [TowerTalk] Mast Material

Subject: Re: [TowerTalk] Mast Material
From: Eric Dobrowansky K2WD <>
Date: Wed, 9 Mar 2011 20:52:27 +0000 (UTC)
List-post: <">>

Wow,  I just ran some numbers thru this online utility, and the results vary 
wildly from the older ARRL Antenna Mast Analyisis Excel sheet I found online a 
year or so ago. 

Can anyone tell me the correct stress PSI of the US Tower M20R reinforced 
mast?  I would like to know the true ratings of this mast I have in use here at 
the moment.  





Here is a neat mast calculator: 

Plugging in some numbers for 1.5" schedule 20 water pipe: 
Safety factor f   2 
Wind loading factor k  .004           lb/ft2/mph2 
Maximum stress S       30,000      psi 
Outside diameter D        1.9     in 
Inside diameter d        1.61     in 
Total length of mast          8   ft 
Height above support h       4      ft 
Antenna 1 height h1          4   ft     area a1  6.1       ft2 
Antenna 2 height h2             ft     area a2         ft2 
Antenna 3 height h3             ft     area a1         ft2 

Survival velocity:     63.0 mph 
Failure velocity:     89.1 mph 
Weight of mast:     21.79 lbs 
As indicated above, I wouldn't be confident in using Sch 20 water 
pipe.  That 30,000 psi yield strength for water pipe is hard to 
prove, because water pipe is not specified for structural 
purposes. Also, the last time I priced water pipe, I was amazed 
to see how expensive it had become. 


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