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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
>
>
> 
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> 
-- 
Wolfgang Hasper
Beckstra�e 87
64287 Darmstadt
06151-4289333

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