[TowerTalk] CUTTING MOLLY TUBE

Kevin Adam n9iww at live.com
Sun Jul 27 12:03:50 EDT 2014 

GO RENT A CONCRETE SAW WITH AN ABRASIVE BLADE IN IT SINCE THE SAW IS A CHAIN 
SAW ENGINE YOU COULD LAY IT FLAT TO CUT THE TUBE.
N9IWW

-----Original Message----- 
From: towertalk-request at contesting.com
Sent: Sunday, July 27, 2014 12:00 PM
To: towertalk at contesting.com
Subject: TowerTalk Digest, Vol 139, Issue 44

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Today's Topics:

   1. Re: Cutting 2" Heavy Wall Cr-Mo Mast Up on Tower (Grant Saviers)
   2. Fwd:  Cutting 2" Heavy Wall Cr-Mo Mast Up on (Jim Thomson)
   3. Re: Cutting 2" Heavy Wall Cr-Mo Mast Up on Tower (Pete Smith N4ZR)


----------------------------------------------------------------------

Message: 1
Date: Sat, 26 Jul 2014 22:24:28 -0700
From: Grant Saviers <grants2 at pacbell.net>
To: Charles Gallo <charlie at thegallos.com>
Cc: "<towertalk at contesting.com>" <towertalk at contesting.com>
Subject: Re: [TowerTalk] Cutting 2" Heavy Wall Cr-Mo Mast Up on Tower
Message-ID: <53D48D0C.6070700 at pacbell.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

If the CrMo is heat treated (and as hard as it should be) then all you
will get is a dull blade in a portable bandsaw.  A carbide tipped blade
may work, but are fragile, a tungsten carbide abrasive coated blade will
definitely work, but $$.  Several cutoff blades 4 1/2" grinder will also
get it done, but why and how safely, and where is the cut off piece
going to go?

Grant KZ1W


On 7/26/2014 10:56 AM, Charles Gallo wrote:
> Cordless portable bandsaw
>
> --
> 73 de KG2V
> Charlie
>
>> On Jul 26, 2014, at 1:47 PM, "Victor Walz" <n2pp at frontiernet.net> wrote:
>>
>> I have a 22 ft (2" OD) heavy duty Cr-Mo mast presently installed up on a 
>> 100
>> ft Rohn 45 tower.  It weighs 200+ pounds. I previously had a 4 el 20 
>> meter
>> yagi stacked 12 ft.  above a 40 meter F12  yagi.  I just finished 
>> removing
>> both antennas for repairs and have decided not to reinstall the stack due 
>> to
>> the complexity of the installation.    I will be re-installing the 40 
>> meter
>> yagi and some VHF antennas on this tower.  Consequently, I would like to
>> shorten the 22 ft mast by 10 ft.
>>
>>
>>
>> I am looking for advice on the most efficient way to cut this very thick
>> high strength mast in place.  I would prefer to use battery-operated 
>> tools
>> such as a reciprocating saw(metal blade?) or a grinding tool (cutting
>> wheel?).  I can run 120 VAC (about 200 ft extension cord) up the tower if
>> needed.
>>
>>
>>
>> What would be the optimum method for cutting this mast without excessive
>> tower time?  Thanks in advance for any responses.
>>
>>
>>
>> Vic,  N2PP
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
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> http://lists.contesting.com/mailman/listinfo/towertalk
>



------------------------------

Message: 2
Date: Sun, 27 Jul 2014 03:13:32 -0700
From: "Jim Thomson" <jim.thom at telus.net>
To: <towertalk at contesting.com>
Subject: [TowerTalk] Fwd:  Cutting 2" Heavy Wall Cr-Mo Mast Up on
Message-ID: <E81B3A33156F4DAA8EC13E369C2EA783 at JimPC>
Content-Type: text/plain; charset="utf-8"

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



------------------------------

Message: 3
Date: Sun, 27 Jul 2014 10:55:40 -0400
From: Pete Smith N4ZR <n4zr at contesting.com>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Cutting 2" Heavy Wall Cr-Mo Mast Up on Tower
Message-ID: <53D512EC.1040205 at contesting.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I would leave it - in case you ever decide to do something else, you
can't uncut the mast.

73, Pete N4ZR
Check out the Reverse Beacon Network at
http://reversebeacon.net,
blog at reversebeacon.blogspot.com.
For spots, please go to your favorite
ARC V6 or VE7CC DX cluster node.

On 7/27/2014 1:24 AM, Grant Saviers wrote:
> If the CrMo is heat treated (and as hard as it should be) then all you
> will get is a dull blade in a portable bandsaw.  A carbide tipped
> blade may work, but are fragile, a tungsten carbide abrasive coated
> blade will definitely work, but $$.  Several cutoff blades 4 1/2"
> grinder will also get it done, but why and how safely, and where is
> the cut off piece going to go?
>
> Grant KZ1W
>
>
> On 7/26/2014 10:56 AM, Charles Gallo wrote:
>> Cordless portable bandsaw
>>
>> -- 
>> 73 de KG2V
>> Charlie
>>
>>> On Jul 26, 2014, at 1:47 PM, "Victor Walz" <n2pp at frontiernet.net>
>>> wrote:
>>>
>>> I have a 22 ft (2" OD) heavy duty Cr-Mo mast presently installed up
>>> on a 100
>>> ft Rohn 45 tower.  It weighs 200+ pounds. I previously had a 4 el 20
>>> meter
>>> yagi stacked 12 ft.  above a 40 meter F12  yagi.  I just finished
>>> removing
>>> both antennas for repairs and have decided not to reinstall the
>>> stack due to
>>> the complexity of the installation.    I will be re-installing the
>>> 40 meter
>>> yagi and some VHF antennas on this tower.  Consequently, I would
>>> like to
>>> shorten the 22 ft mast by 10 ft.
>>>
>>>
>>>
>>> I am looking for advice on the most efficient way to cut this very
>>> thick
>>> high strength mast in place.  I would prefer to use battery-operated
>>> tools
>>> such as a reciprocating saw(metal blade?) or a grinding tool (cutting
>>> wheel?).  I can run 120 VAC (about 200 ft extension cord) up the
>>> tower if
>>> needed.
>>>
>>>
>>>
>>> What would be the optimum method for cutting this mast without
>>> excessive
>>> tower time?  Thanks in advance for any responses.
>>>
>>>
>>>
>>> Vic,  N2PP
>>>
>>> _______________________________________________
>>>
>>>
>>>
>>> _______________________________________________
>>> TowerTalk mailing list
>>> TowerTalk at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/towertalk
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>



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