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on 8/31/04 7:37 PM, Renee Mattie at reneemattie@HOTMAIL.COM wrote:

> Ken Gebhart wrote:
>
>> Under the heading of not doing anything dumb, I would
>> recommend not doing two things.
>> Do not take the arm out of
>> the frame, or move any screws associated with this area other
>> than removing a cover to apply lubricant.
>> Final assembly is done in the factory with the sextant on a
>> testing machine.
>> Set screws are adjusted to center the pivot exactly during
>> the test.
> Thanks for this warning.  One would think, looking at the
> cover of Bruce Bauer's "The Sextant Handbook", that removing
> the arm from the frame is OK.
>
>> The other area which I would not disturb is the
>> worm gear, other than to clean and lubricate.  I have always
>> found that to disassemble and re-assemble any kind of gearing
>> invites the prospect of mismatching of teeth or axes which
>> results in high and low spots of tactile feedback, new wear
>> patterns, or other mysterious results that just don't seem right.
>
> Thanks for this warning, too.  Are you saying that it would be a
> bad idea to remove the drum from the arm for cleaning, or just
> that it would be a bad idea to take apart the innards of the drum?
>
Renee,

I simply think less is better. After the sextant is tested at each 10 deg.
interval on the arc, then the drum is rotated each 5 deg. and tested for
accuracy.  This is called the eccentricity test, and if out of tolerance,
the worm gear is either rejected or re-seated in its holding assembly in
hopes that the test results can be improved.  The point is that everything
is in its place for the test. Theoretically, if you took it all apart and
re-assembled it, it would call for another final test, which of course you
do not have the tools for.

Ken

   

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