[TowerTalk] Mast Material

[Jim Thomson]

Date: Wed, 9 Mar 2011 20:52:27 +0000 (UTC)
From: Eric Dobrowansky K2WD <k2wd at comcast.net>
Subject: Re: [TowerTalk] Mast Material


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 

##  The US tower corp mast is  made from 35 ksi material.... [ per their online Q+A].     They have just stuffed one tube inside the other..and then but welded em. 

##  IMO, if ur  going to use steel.. use real steel.  My mast is  2" OD x  .375"  wall    and is  107 ksi  heat treated 4130  chromolly steel.  
The ideal mast is 3" OD  or  2.875"  OD.. with a 1/4"  thick  wall..and at least  87 ksi.    A  2.875" OD mast + 1/4"  wall  weighs the SAME  7 lbs per foot as 
my 2"  OD  x .375"  wall  mast.     Yet the section modulus of the 2.875"  x  .25"  wall   tube is  a helluva  lot bigger than my 2" x .375" mast.  

## In fact the  2.875" OD  x .25"  wall mast  [ 87 ksi]   is still stronger than my 2" Od x .375" wall ,107 ksi mast..even though the yierld on the bigger od mast is LESS. 

## tashi towers sells  2"  Od x  .375" wall masts  in 120,200  psi.     The UST version is only 107 ksi  [ and a LOT more $$$] .   Array solutions sells both chromolly [ 104 ksi]
and 1026 dom masts [ 87 ksi] .    Don't go cheap here, you will kick urself.   A good mast is a good investment...esp if you want to  install more/bigger ants  down the road.   

Later...... Jim   VE7RF