[TowerTalk] 2 inch Chrome Moly mast needed

[Jim Thomson]

Date: Thu, 7 Apr 2016 06:34:30 -0400
From: "john at kk9a.com" <john at kk9a.com>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] 2 inch Chrome Moly mast needed

If you really need that much strength, consider a 3" 1026 DOM mast. Your
tower is not made of chrome moly why does your mast need to be? I cannot
imagine why 2" is the standard. Do you really want to climb 15 feet of 2"
tubing?

John KK9A

##  2 inch OD  x .375 chromolly tubing weighs the same as 3 inch OD x .25
chromolly tubing..and they both cost the same. Aprx 7 lbs per foot. 

##  The strongest thing up there should be the mast, bar none.   Have you ever
seen a mast failure ?   Total gong show.  Imagine a mast, folded at 90 degs, right
above the top of the tower...with yagis mounted on it.   Now what are you gonna do ?  
Tower stays intact of course, but the folded mast is a complete mess.

##  Now you are into a very expensive crane job.  In a lot of cases, a crane flat out wont
fit in where you want it, or tower is too high,  too many trees and junk in the way of the crane,
or the boom angle on the crane is too shallow etc, etc.     Then  when you finally get the
bent mast removed, and destroy most of your yagis + coax, etc in the process, then what
happens is  now you have to rebuild the entire array.     So you end up buying a 3 inch  x 
.25 wall   chromolly mast anyway, then have to buy mating 3 inch bearings, 3 inch mast clamps
etc.   All you are doing is delaying the inevitable. 

##  Just buy the  3 inch OD  x .25  wall   heat treated Chromolly mast from dx eng..and be 
done with it.  All galvanized.  It’s a superb investment.   And you will have zero problems down
the road if you have to sell it.   Cap the top so water does not flow down the inside..which offers
a bit of protection to the rotor, top bearing assy. 

##  Typ 1026 DOM masts are  2.875 OD  x .25 wall, also galvanized.   Yield strength on the version that 
array solutions sells is 87 ksi.      The CM version sold by dx eng is aprx 107 ksi.   The problem with
2.875 od material is getting mating bearings for it.  Also a lot of rotor mast clamps  are for 3 inch,
and would have to be shimmed.   kurt andrress  will custom make a 2.875 mast clamp  for stuff
like  PP rotors  or OR-2800  etc, etc.  

##  do it right the 1st time.  Then install mast steps so you can safely climb the mast. 
Pay once, cry once..but do it right. 

##  Run the mast calcs  for  87 ksi 1026 DOM  in a 2.875 x .25 wall.....VS 
107-115 ksi 4130 CM  in a 3.00  x .25 wall...and you will be amazed. 

Jim   VE7RF