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    Re: MHR1 dimensions and details
    From: Gary LaPook
    Date: 2009 Sep 24, 13:22 -0700

    I handled some of them in London in July. To lock the tubes you turn
    the knob less than i/4 turn,< 90 degrees. Based on my manipulation of
    the device I believe that it does work in the manner I described in
    July, see:
    
    http://www.fer3.com/arc/m2.aspx?i=109056&y=200907
    
    gl
    
    On Sep 24, 12:59�pm, Wolfgang Hasper  wrote:
    > Does anybody have more pictures with details of MHR1, detailed dimensions
    > etc.? (more than contained in RvR's and Svarovski's papers)
    > I am thinking of making some cad drawings and/or a digital model.
    > In the end this may lead to a (functional, not fac-simile) replica maybe using
    > rapid prototyping techniques. (one reason is that it seems really difficult
    > to get hold of suitably sized tubes.)
    > Does anybody have additional information on the locking mechanism? My guess
    > is, that there must be a knee-lever mechanism across the diameter of an
    > end-cap in the inner tube (knee-lever is self-locking, can be actuated with
    > just a slight turn on the knob) that is forced aginst the inner wall of the
    > intermediate tube.
    > Couldn't anybody in possession of such a device go to the nearest airport and
    > ask security to scan it ;o) �?
    >
    > Wolfgang
    >
    >
    >
    > > 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
    >
    > > Linked File:http://www.fer3.com/arc/imgx/IMG_2095.JPG
    > > Linked File:http://www.fer3.com/arc/imgx/Copy-of-IMG_2100.JPG
    > > Linked File:http://www.fer3.com/arc/imgx/IMG_2097.JPG
    > > Linked File:http://www.fer3.com/arc/imgx/IMG_2098.JPG
    > > Linked File:http://www.fer3.com/arc/imgx/IMG_2170.JPG
    > > Linked File:http://www.fer3.com/arc/imgx/IMG_2188.JPG
    > > Linked File:http://www.fer3.com/arc/imgx/IMG_2192.JPG
    >
    > --
    > Wolfgang Hasper
    > Beckstra�e 87
    > 64287 Darmstadt
    > 06151-4289333
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