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.
Thanks
Eric
K2CB
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Here is a neat mast calculator:
http://www.math.niu.edu/KARC/mast/
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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