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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:https://www.NavList.net/imgx/IMG_2095.JPG
> > Linked File:https://www.NavList.net/imgx/Copy-of-IMG_2100.JPG
> > Linked File:https://www.NavList.net/imgx/IMG_2097.JPG
> > Linked File:https://www.NavList.net/imgx/IMG_2098.JPG
> > Linked File:https://www.NavList.net/imgx/IMG_2170.JPG
> > Linked File:https://www.NavList.net/imgx/IMG_2188.JPG
> > Linked File:https://www.NavList.net/imgx/IMG_2192.JPG
>
> --
> Wolfgang Hasper
> Beckstra�e 87
> 64287 Darmstadt
> 06151-4289333
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