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    Re: Manufacture new Bygraves?
    From: Gary LaPook
    Date: 2009 Jul 03, 13:32 -0700

    These are pictures of the completed slide rule. the second picture shows the cursor set to 82 on the tan scale and to 57 on the cosine scale.
    The first picture shows the rules for its use mounted below the tan scale.

    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---.com>/* wrote:
        From: Greg Rudzinski <gregrudzinski---.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...{at}clear.net.nz
        </mc/compose?to=engin...{at}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?

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