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Re: [TowerTalk] G-1000DXA failure with lower mast clamp

To: Barry N1EU <>, Tower Talk List <>
Subject: Re: [TowerTalk] G-1000DXA failure with lower mast clamp
From: Kevin Normoyle <>
Date: Tue, 27 Dec 2011 09:36:35 -0800
List-post: <">>
On 12/27/2011 8:12 AM, Barry N1EU wrote:
> >>>  I'd also appreciate comments on why this happened in the first place
> >>>  and how to prevent a repeat.  The rotor was assembled to factory
> >>>  instructions with lock washers.  Instead of using anti-seize on those
> >>>  four bolts, perhaps what is really needed is loctite?

I put up a G-800 in the last year with a lower mast clamp.
If I remember right, I had to swap out the bottom bolts that came with the 
with longer bolts, when the mast clamp was used.
I had the green bolts sitting around from some other time, so I'm not sure if 
normally the longer bolts come with the mast clamp or what.

what length bolts did you interesting to measure the thickness of the 
mast clamp and the depth of the holes, and figure out if you had the max length 
bolt length possible

the way the Al broke off has me wondering. I thought the holes were deeper than 
unless that happened after loosening. Then it's just a loosening problem.

Yaesu has some formulas for using rotators with mast clamps. They severely 
derate the tolerable load on the rotator.

Come to think of it, it's hard to believe that a 3 element Steppir meets the 
Yaesu limits with a mast clamp

they say [Antenna Wind Load Area] * [Height of antenna mast] = 0.45
(wind load is in m**3 and height of mast is in m.

what's a 3 element Steppir? 6.1 sq ft is 0.56 sq meters

they also recommend 60% of the max for margin.

So maybe it's just overloading a pole mount.


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