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    Re: Another cylindrical bygrave
    From: Gary LaPook
    Date: 2010 Jan 21, 23:59 -0800
    In deciding the size of tubes to procure for making reproductions I would like to suggest you use tubes similar to the ones I have used. The cotangent tube is 1.500 inches O.D, (38.18 mm), 1.460 in. I.D (37.74 mm) I.D. The locking mechanism's rubber friction ring adjusts from 1.482 in. to 1.680 in. (37.6 to 42.7 mm) so a cosine tube with an I.D. in this range can be made into a reproduction of an HR-1 as well as a Bygrave. The I.D. of my cosine tube is 1.634 in. (41.5 mm) so works well but I would like to find a tube that was more close fitting to the cotangent tube and scale, 1.520 in. (38.46 mm). The off-the-shelf components I used for my locking mechanism also comes in larger sizes, 2, 3 and 4 inch ( 51, 76 and 102 mm) models so would fit tubes with I.D.s approximating those sizes so picking such tubes would also allow the option of making an HR-1 reproduction too.


    Hein Bodahl wrote:
    My apologies for going off topic.
    I renamed my answer from "[NavList] Re: Cylindrical Slide Rule tube poll"
    I have read the posting earlier and the version you describe is of
    course the inspiration for my idea. However it seems to me that the
    described version still would suffer from the problem of locking the
    scales while resetting the cursor. Mine would on the other hand, not be
    Also, using shrink wrap tubes would eliminate the problem of "snagging"
    along the seems.
    The cursors printed on transparency sheets, laminated for stiffness.
    Properly cut and shrink wrapped around the tube I believe that it could
    make a better transparent outer tube than the adhesive pouch solution.
    Accurate cutting could possibly ensure proper friction.
    The simple beauty and extraordinary easy production and storage of your
    flat Bygrave is unfortunately slightly inhibiting of actual prototyping :-)
    On 21.01.2010 13:01, Gary LaPook wrote:
    Hein Bodahl wrote:
    I have been thinking about using a 50 or 75mm drain pipe and fixed
    Around that I would shrink wrap a movable cursor for the cos scale. This
    transparent wrap, lined to avoid undue friction, would also cover the
    cotan scale.
    Around the wrap covering the cotan scale I would wrap a second, movable
    cursor for the cotan scale. This second cursor would then move in
    conjunction with the cursor for the cos scale, once set, avoiding the
    locking problem.

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