I noticed that a used G2800 I bought had Helicoil inserts in the base
holes. I don't know if this was a retrofit or factory install. In
either case, Helicoils substantially increase bolt pull out ratings in
aluminum. So I would suggest that part of the fix is to install
Helicoils in the good three holes. You can buy a kit of inserts, the
special tap, insert inserter, and correct drill at auto stores or on
ebay (or MSC or McMaster). Another advantage is that Loctite thread
locker will work well on the stainless steel inserts where it is less
effective on aluminum in the grades commonly available. The blue,
medium strength is what I would use since disassembly will be possible.
The Helicoil inserts are available in various lengths, so in may be
possible to drill deeper than the stock holes and insert a longer
insert. Usually 4 or 5 full thread engagements provide full strength in
aluminum so that may work for the broken hole. Given the bottom is a
die casting I would try for more threads engaged. I note the stock
holes and bolts are at the low end of enough thread engagement on the 3
Yaesu rotators I have, even with a supply of 8mm bolts in various
lengths. I would add that the insert drilling and tapping should
definitely be done on a drill press or better.
If that won't work then the damaged hole fix gets more difficult.
Depending on the base material it may be possible for a heliarc welder
to rebuild the material and then Helicoil it. Another alternative is
high strength metal filled epoxy, there are some pretty good ones.
McMaster has several, see
http://www.mcmaster.com/#catalog/117/3378/=fjpiwm P/N 7500A4
The epoxy fill plus a Helicoil as deep as possible into the remaining
good aluminum might be ok if the other bolts are tight.
Or course, first check the cost of a new base. Since the potential
damage with another failure is high, this might be the best fix.
Grant KZ1W
On 12/27/2011 6:19 AM, Barry N1EU wrote:
> I should have mentioned that in the photo, the right two shots of the
> mast clamp show zero damage to the mast clamp itself. The left shot
> shows the one damaged bolt hole on the rotor itself.
>
> On Tue, Dec 27, 2011 at 2:16 PM, Barry N1EU<n1eu.barry@gmail.com> wrote:
>> My G-1000DXA rotor came completely unhinged from its GC-038 lower mast
>> clamp and left my 3-el Steppir and attached rotor dangling from the
>> attached cables. It appears that the attachment bolts on the bottom
>> of the rotor came loose and fell out. Please see photo at
>> http://n1eu.com/g1000.jpg
>>
>> The cast aluminum fractured at one of the four threaded holes on the
>> rotor bottom. At first I thought this might be the cause of failure
>> but on further thought, I would guess that the other 3 bolts came
>> loose and fell away and this fourth bolt was the last to stay attached
>> and this caused the aluminum fracture. Any comments on whether this
>> seems correct?
>>
>> 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?
>>
>> Does the motor casing need replacement and if so, is this a fairly
>> easy job to do myself? There's still about half the threads on the
>> one hole that suffered the fracture.
>>
>> Thanks& Happy Holidays,
>> Barry N1EU
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