[TowerTalk] Fwd: Cutting 2" Heavy Wall Cr-Mo Mast Up on

[Jim Thomson]

Date: Sat, 26 Jul 2014 14:27:25 -0400 (EDT)
From: Hans Hammarquist via TowerTalk <towertalk at contesting.com>
To: towertalk at contesting.com
Subject: [TowerTalk] Fwd:  Cutting 2" Heavy Wall Cr-Mo Mast Up on
Tower

Beside wonder how you are going to handle the cut-off piece, I would try a regular tube cutter. I am using one with carbide wheels and that seems to cut anything. Nothing but hand power is used.


Good luck but be careful.


Hans – N2JFS

##  His 22 foot mast weighs  200++ lbs.......which implies it has a  half inch thick wall thickness.    A  2 inch od mast..with a .375 inch wall is  only 7 lbs per foot.    No way in hell you are  gonna cut 4130  heat treated
chromolly steel, with a half inch thick wall...with any tubing cutter.  

##  BTW,  once the mast is  .25 inch thick,   going any thicker is really a waste of effort.   At that point you should use a bigger OD mast, like   2.5  or  even 3.0 inch OD.    A  2 inch mast with a .375 inch thick wall,
weighs the same as a 2.875 inch mast with a .25inch wall thickness.....  both of em weigh the same 7 lbs per foot.   The 2.875 inch od mast will be one helluva lot stronger, even factoring in the bigger diam masts  windload.   And that assumes the  2.875 inch mast is  DOM, with 89 ksi yield strength..... vs the 2 inch mast with its .375 wall  being made from 4130 chromolly steel with  107 ksi yield. 

##  I use a 2.0 inch od mast with a .375 wall thickness...... cuz its stronger than a 2 inch mast  with a .25 wall.  However, that was not my choice..since the  HDX-689  I bought used was all setup for a 2 inch mast.   If I was doing this  from scratch,  I would opt for either a 2.875 inch od x .25 inch wall  DOM mast..... or a 3.0 od mast with a .25 inch wall...made from 4130 chromolly steel.   The strongest mast I ever heard about was 3 inch OD  with a .375 wall..made from 4130 chromolly.   That mast would weigh 10 lbs per foot..same as the fellow with his  2 inch od mast and .5 inch thick wall. 

## U can see the effect right away using any of the popular mast programs.   watch out, the DOM stuff  will vary from 75 ksi  to  89 ksi..depending on where you buy it.   4130 chromolly  will vary from 107 ksi  up  to 125 ksi.   The yield strength  makes  a huge difference of course.    Section modulus  x yield strength  =  bending moment. 

Jim   VE7RF