Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Cleaning and protecting my Freiberger
    From: Ken Gebhart
    Date: 2004 Aug 30, 15:54 -0500

    on 8/30/04 1:19 PM, Renee Mattie at reneemattie{at}HOTMAIL.COM wrote:
    > I have just bought myself a Freiberger drum sextant,
    > used, made in 1976. I am happy with its overall condition.
    > It works well.  Other than a few scratches in the middle
    > of the frame, nothing looks terribly worn. I want to start
    > out on the right foot with it, of course.
    > If anyone has any tips or warnings to offer on disassembling
    > and reassembling this sextant, I'd really appreciate learning
    > more about it.
    > Why would I want to do this?  There is a small amount of corrosion
    > on some of the screws.  I think the thing to do is to remove
    > the scope, mirror, and shade assemblies, wash the sextant
    > to remove particles, the completely disassemble it for a
    > more thorough cleaning, coat the non-moving parts
    > (including screw threads) before reassembly to prevent
    > corrosion, and lubricate the moving parts.
    > So far, I have only been bold enough to remove the handle
    > by unscrewing the upper leg stub and the large lower
    > screw.  I see a waxy substance in the screw holes.
    > I have no way of knowing if it was ORIGINALLY waxy,
    > or if this is a grease that has gone waxy with age.
    > In this forum, I have seen the following recommended
    > for protection from galvanic corrosion:
    > * Never-Seize
    > * Lanocote
    > * TefGel
    > * Krytox with corrosion inhibitors(which Jared Sherman
    > frequently recommends highly for a number of reasons)
    > I don't see any recommendations for:
    > * Hydrophobic dry coatings (like sailkote, which contains Krytox)
    > and I wonder why.  Jared Sherman is of the opinion that these
    > spray-on coatings just don't last very long.
    > I am eager to take the sextant apart, but I want to be
    > prudent.  I understand how to create a proper workspace,
    > label and lay out each and every part, put screws back into
    > same holes they come from, and take pictures along the way
    > to remind me what it ought to look like when I'm done.
    > It's just that I've never done this before, and there is no
    > shop manual.  It looks like a straightforward job, but I
    > really would appreciate hearing more from anyone who can
    > give me a heads-up on any stupid thing a beginner is likely
    > to do wrong.
    > And I am up in the air about what to put on the screws before
    > I put them back in.
    > Thanks for your help!
    > Renee
    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.  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.
    Ken Gebhart

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site