[TowerTalk] Mast pipe: To pin or not to pin?

Mike Bragassa bragassa at consolidated.net
Fri Aug 25 15:54:49 EDT 2006

Your choice, of course.
In Casper, Wyo w/ their gusty 60-70 mph Chinook winds, I had to pin the mast 
pipe or I would be re-aligning it every week. (TH7DXX and 40-2CD) One time 
it "May-poled"  a bunch of times and almost tore the connector out of a 
balun.. That's when I started pinning the mast pipe to the rotor clamp. 
Also, this was w/ Tail-Twister rotors and later, Create's.
When I moved and setup here in South Texas I asked around about pinning the 
mast pipe. It seemed that no one did. "Let it serve as a shear-pin. Winds 
here in South Texas are not bad; except if a hurricane hits; then you have 
other problems."
Therefore, w/ no pinning:
With 2 stacked Yagi's ( T-12  and a KLM 3 ele 40...and a Create rotor) it 
has never rotated in the rotor clamp; even last year in the near fringes of 
Hurricane Rita w/ 85 MPH winds.
In your case; with no more wind load ( one 3 ele Yagi) than you are talking 
about and 50-60 MPH winds; I would not pin your mast pipe. Also, it will 
serve as a shear-pin in case the Hygain brake breaks. Just make sure you 
torque down your clamp bolts adequately.

I would be a little concerned about that "9 foot 0.25 wall aluminum mast", 
though. I think the 'norm' is to double the wall thickness when going from 
steel to aluminum. Perhaps, only "4-1/2--5 feet above the tower"  will be 
your salvation?

Mike, K5UO

Subject: [TowerTalk] Mast -- Drill or not?
To: towertalk at contesting.com
Message-ID: <44EEDD55.13591.1C5BE72 at wa3afs.inav.net>
Content-Type: text/plain; charset=US-ASCII

I am just about to start installing my 9 foot roof tower with an 1/4 inch 
wall aluminum mast (9 foot) with a 3 element
SteppIR mounted about 4 1/2 to 5 feet above the tower.

Is the center bolt on the Ham-IV rotator sufficient to keep the mast from 
turning or should the mast be drilled so that
the bolt (or an pointy end bolt) has a more positive hold on the mast? 
Winds of 50-60 mph are occasional in the

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