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

To: Tower Talk List <>
Subject: Re: [TowerTalk] G-1000DXA failure with lower mast clamp
From: Barry N1EU <>
Date: Tue, 27 Dec 2011 18:22:10 +0000
List-post: <">>
The original bolts are lost now but the GC-038 doc calls out M8 X 25mm
long bolts.

The holes are deeper - there's still probably a half inch or more of
threaded hole deeper than what is broken off on that one hole.  And
yes, I now believe it was just a loosening problem and my current plan
is to use Nord-Lock lockwashers and reassemble with correct length

Barry N1EU

On Tue, Dec 27, 2011 at 5:36 PM, Kevin Normoyle
<> wrote:
> 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
> G-800 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 that.
> 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.
> -kevin
> ad6z

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