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    Re: Manufacture new Bygraves?
    From: Gary LaPook
    Date: 2009 Jul 09, 20:24 -0700
    I went to Home Depot and bought a "test plug" for a 1-1/2' pipe, $3.50. They also had 2", 3" and 4" models. With the wing nut loose the diameter of the rubber ring is 1.482" and with the wing nut tightened it enlarges to 1.680" an increase  of .198" or 5mm. So you  turn the cap down to fit in the the bottom end of the cotan tube so that the rubber protrudes below the bottom end of that tube. Glue the cap into the cotan tube since it will take only the anti-rotation, minimal load. Then add a longer bolt with another tube surrounding the bolt inside the cotan tube to take the compressive load and, voila, you have it. You could make it look better by replacing the wing nut with something prettier but you get the idea.


    glapook@pacbell.net wrote:
    If you go to a plumbing supply house you can buy a device for capping
    off pipes that consists of a cap with an extension that protrudes
    inside the pipe. Turning a screw in the center of the cap causes this
    extension to expand and lock itself firmly inside the pipe thereby
    sealing the pipe. I was pondering if this "off the shelf' item could
    be adapted to hold the two scales immobile like the mechanism in the
    That said, the reproductions I have made by forming a plastic tube
    containing the cosine scale out of page protector sheets do not
    exhibit any such problem, they fit together tightly enough so that
    friction is quite sufficient to keep the scales in alignment.
    On Jul 9, 6:23 am, Brad Morris <bmor...@tactronics.com> wrote:
    Hi Bill
    I certainly can send you photos of my MHR-1.
    The locking mechanism is internal to the tubes and I believe to be a cam mechanism, but have NOT opened up the tubes to see the inside.  In order to replicate the device, we would have to take it to pieces and have a Mechanical Engineer create a drawing package.  I do have on one staff who I would trust to perform this work.
    My view is that since it was put together, I can probably take it apart and put it back together.  This would naturally be a high risk activity, so I want to be sure that we are going to proceed all the way to fruition.
    Best Regards
    -----Original Message-----
    From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of engin...@clear.net.nz
    Sent: Thursday, July 09, 2009 1:55 AM
    To: NavList@fer3.com
    Subject: [NavList 9039] Re: Manufacture new Bygraves?
    Brad and others
    There certainly seems to be some interest.
    What I had in mind was a small consortium to make a few replicas of the Bygrave position line slide rule. Gary LaPook has shown that it is possible to produce the scales, something that works like one and much more. I was thinking of producing something that looks like an original Bygrave, made from similar or same materials (with the possible exception of the scales). I was not thinking of marketing and manufacturing for profit (much), but rather at cost just for those members who wanted one.
    Do you think, Brad, you could send me some dimensioned sketches of your genuine Bygrave, off list if you prefer, with notes about what you think the materials might be? A close up picture of part of the scales would be useful too, for those who want to think about making the scales with the same fonts. I could then perhaps put together  a materials list and see what people could do and where.
    Bill Morris
    New Zealand
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