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    Re: Manufacture of Bygraves
    From: Tom Sult
    Date: 2009 Aug 17, 21:32 -0500

    I had it on my watch list... Too rich for me!
    
    Thomas A. Sult, MD
    Sent from iPhone
    
    On Aug 17, 2009, at 4:43 PM, Gary LaPook  wrote:
    
    >
    > The MHR1 just sold for 1990 pounds, $3300 US, way out of my price
    > range.
    > I am glad that I got to hold three of them in my hands last month in
    > London.
    >
    > gl
    >
    > Brad Morris wrote:
    >> http://cgi.ebay.com/U-Boat-MHR-1-Dennert-Pape-Sextant-Calculator-Slide-Rule_W0QQitemZ140338425807
    >>
    >> currently on eBay.  Looks like a very nice one.
    >>
    >> For all the talk of the Flat Bygrave (hat's off Gary), there is
    >> nothing, absolutely nothing like the feel of this solidly made, top
    >> rank instrument.  I recommend it highly!
    >>
    >> Best Regards
    >> Brad
    >>
    >>
    >> ________________________________________
    >> From: NavList@fer3.com [NavList@fer3.com] On Behalf
    >> Of glapook@PACBELL.NET [glapook@PACBELL.NET]
    >> Sent: Wednesday, August 05, 2009 11:19 PM
    >> To: NavList@fer3.com
    >> Subject: [NavList 9378] Manufacture of Bygraves
    >>
    >> I was in London last month and made arrangements (with the
    >> assistance of Geoffrey Kolbe, thanks again) to see the examples of
    >> Bygraves and the HR series held by the Science Museum and by The
    >> National Maritime Museum. I attach two photos showing my hot little
    >> hand holding examples of each.
    >>
    >> The Bygrave I saw was a Mk II serial number 105, the same one shown
    >> in Van Riet's paper. I measured the diameters of the scales,
    >> actually their circumfrances using a tape measure, and my numbers
    >> are very slightly different than his. I believe my measurements are
    >> accurate to one-half of a millimeter.
    >>
    >> The circumfrances were:
    >>
    >> Cotan   174mm
    >> Cos     187mm
    >> Cursor tube 203mm
    >> Knob at bottom of cosine scale  207mm
    >>
    >> Dividing by Pi gives diameters of:
    >>
    >> Cotan 55.4mm
    >> Cos   59.5mm
    >> cursor 64.6mm
    >> Knob 65.9mm
    >>
    >> I am attaching two photos showing two details of the construction.
    >> One is a photo of the cotan scale showing that it was printed on
    >> paper and then wrapped around the tube. You can see the gap that
    >> has developed over time. The second shows a detail of the long
    >> pointer, it is bent downward to be near the cotan scale to
    >> eliminate parallax.
    >>
    >> The National maritime Museum has three examples of the HR1 and one
    >> example of the larger HR2. The three HR1s were in cans and the HR2
    >> had a cover and was obviously meant to be mounted on a desk. The
    >> first two HR1s I examined were in perfect shape but the third one
    >> (the one I am holding in the picture) was in poor shape. I am
    >> attaching two photos of the HR2 one showing the scale revealing the
    >> same construction method used in  the Bygrave, a paper scale glued
    >> around a tube.
    >>
    >> It was a thrill for me to actually see these instruments. My first
    >> impression was that they are very big compared to the one I
    >> constructed which is only one and a half inches in diameter.
    >>
    >> gl
    >>
    >>
    >> 
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