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: Manufacture new Bygraves?
    From: Gary LaPook
    Date: 2009 Jul 03, 13:29 -0700

    Here are some pictures of the Bygrave replica I am using. The first
    picture, 2891, shows the co-tan scale. When printed the scale only had
    tick marks every 10 minutes and I added some 5 minute marks near each
    end of the scale. I used the periodicity of the scale to figure out
    where to place these tick marks. For example, to place the mark for 89º
    15' I took its tan,  76.39, divided by 10, 7.639, and took the arc tan
    of that giving me 82º 32'. I used the mark for that value (visually
    interpolating) and with the use of a t-square I placed the mark for 89º
    15' directly above it. I also hand labeled a number of tick marks to make
    it easier to find the value I was looking for.
    Picture 8292 shows the scale along side of the 12 inch drain pipe that I
    mounted the scale on.
    Pictures 8297 and 98 shows all three components, the tube with the
    co-tan scale mounted and covered in clear plastic sheet; the cosine
    scale sealed between two sheets of plastic formed into a tube and the
    sheet of plastic formed  into a tube and marked as the cursor.

    Gary LaPook wrote:
    I have had great success with printing the scales of the flat Bygrave
    and wrapping them around a tube and sealing them in place with clear
    adhesive plastic sheets.
    Here are some pictures of one example:
    Links to the scales:
    I picture of one made by Geoffrey Kolb:
    Try it.
    Hanno Ix wrote:
    I agree. Bygraves could be build.
    However, there are some cumbersome questions, the most obvious being,
    How to generate a drum-shaped scales with the required accuracy and
    resolution. Remember, we will have to maintain sub-millimeter acc/res
    over many turns, with "many" meaning perhaps 20 to 50. This should be
    possible, but is still not easy.
    If someone could generate the mechanical construction and quality
    assurance methods for this challenge we could talk about manufacturing
    more seriously. Her are my ideas:
    Personally, I am thinking of an ink-jet head printing on a turning
    drum where the printing is synchronised with a digital encoder on the
    drum' s axis. The process control could be handled by one of the
    relatively simple contollers on the market.
    Another approach would be to replace the ink-jet printing with an
    engraving system.
    With the first  I personally have experience, with the second none
    However, more problems lurk. What are the limits for excentricity of
    the drums when in use? How about friction? How to stabilize the thing
    when under the influence of temparature changes, humidity, sun's UV,
    spray salt water, etc, etc.
    So, you can see that the conceptual simplicity of the Byraves is
    offset by many practical obstacles.
    Compare this, for instance, with the Ageton method (H.O. 211)! Only 12
    pages of a table, a sheet of paper and a pencil is virtually all you
    need to get a generally higher res/acc than with a practical Bygrave.
    Yes, you will also need the skill and concentration to exercise the HO
    211 calculations under virtually any condition at sea - particularly
    when you are a submarine commander at war. Well, I guess, in this case
    a Bygrave, well designed under a government contract, does make sense!
    --- On *Fri, 7/3/09, Greg Rudzinski /<gregrudzinski@yahoo.com>/* wrote:
        From: Greg Rudzinski <gregrudzinski@yahoo.com>
        Subject: [NavList 8924] Re: Manufacture new Bygraves?
        To: "NavList" <NavList@fer3.com>
        Date: Friday, July 3, 2009, 9:40 AM
        There must be a combination of PVC tubing that fits on itself snugly.
        If the white PVC were engraved with black and red scale markings as a
        regular plastic slide rule is then I think you would have something.
        On Jul 3, 12:18 am, <engin...@clear.net.nz
        </mc/compose?to=engin...@clear.net.nz>> wrote:
        > A few years ago, when I and a couple of friends wanted each to
        own a gear hobbing machine, we cooperated. One made the casting
        patterns and saw them through the local foundry, another did the
        heavy machining and I did the small parts like feedscrews and
        their nuts. It occurs to me that several handy people could
        combine their skills to produce replica Bygraves slide rules.
        There will surely be someone who knows where to access tubing in
        which each size nests snuggly in the next largest size, someone
        else will know how to produce hard-wearing replica scales, another
        may be prepared to turn the bobbins at each end and I would
        volunteer to do small bits of metalwork. The results do not have
        to make profits, though a little would be nice. Since there seem
        to be very few surviving Bygraves calculators, one could at least
        have the satisfaction of owning a replica. The starting point of
        course would have to be accurate, dimensioned drawings of an
        original, preferably following the metric system, so the
        manufacturing consortium would not have to be confined to the USA.
        > Any offers/takers?

    Navigation List archive: www.fer3.com/arc
    To post, email NavList@fer3.com
    To unsubscribe, email NavList-unsubscribe@fer3.com





    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