I had to cut off a welded on gear from a 2" X .375" Cr mast - not easy. It
was laying on saw horses on the ground and took me a day or two of on and
off cutting/grinding with a 3 1/2" steel cutting stone to cut the bottom 3"
off. Maybe I wasn't using the right tools, but this 3 1/2" steel cutting
stone had cut anything and everything before.
I say keep the extra mast in the air, or lower your rotator mounting plate
8 - 10 ft inside the tower.
Another option, remove the mast from the tower, sell it or buy/trade for a
shorter one.
Ray,
N6VR
On Sun, Jul 27, 2014 at 3:13 AM, Jim Thomson <jim.thom@telus.net> wrote:
> Date: Sat, 26 Jul 2014 14:27:25 -0400 (EDT)
> From: Hans Hammarquist via TowerTalk <towertalk@contesting.com>
> To: towertalk@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
>
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