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The MHR1, and its larger desktop variant the HR2, have been described
in the book:
K.Kuehn & K.Kleine, "Dennert & Pape ARISTO 1872-1978", Muenchen, 2004.
A 4-page article, in German, by Henning Pohlmann explains the design of
the two instruments, and mentions that between 200 and 300 items have
been produced in all. They were used from 1942 in U-boats operating in
the Atlantic where the lower accuracy -compared to tables - was
considered acceptable.
There exists a 2-page manual in German.

Otto van Poelje
===============

Geoffrey Kolbe wrote:
> As Peter says, there was some discussion of the Bygrave navigational slide
> rule perhaps two years ago....? (The archives will have it.) Zvi Doron,
> sometime member of the list, set about making a copy. I think a couple of
> other list members made copies. Just recently, I also made a copy which
> turned out pretty well.
>
> The slide rules Zvi Doron and I made were actually more a copy of the
> Besteck-H�henrechenschieber MHR1, (literal translation - "Height Calculator
> Slide Set MHR1") which is the German model to which Peter referred. It was
> made just before and during the war by Dennert & Pape.
>
> I wrote an article on the Bygrave slide rule which is in the current issue
> of "Navigator's Newsletter". As research for the article I went down to
> London to the Science Museum and the National Maritime Museum (or rather,
> the respositories of both these museums where items not on view are stored)
> to look at examples of these instruments. The MHR 1 is obviously a
> derivative of the Bygrave in that it is dimensionally almost exactly the
> same and the scales are laid out in exactly the same way. The only major
> difference is that the inner scale on the MHR 1 is logs of cotangents
> rather than tangents as on the Bygrave. (Why Dennart & Pape should have
> made this change escapes me - possibly to get around Bygrave's patent.) It
> is certainly much better made than the Bygrave and is probably more
> accurate due to the use of  hairline cursor screens rather than metal
> pointers, as used on the Bygrave.
>
> To say the MHR 1 is "the finest cylindrical slide rule made" is perhaps
> misleading, in that the slide rule is dedicated to the purpose of sight
> reduction calculations. The scales are log cotangents and log cosines and
> so it would not be of much good for anything else. It is difficult on a
> cylindrical slide rule to have multiple scales, such as you find on the
> usual linear slide rules which might have anything up to ten different
> scales to use as required. So cylindrical slide rules are not well suited
> for use as general purpose slide rules. But the accuracy of a slide rule is
> dependent on the length of the scale and this is where a cylindrical slide
> rule wins hands down. The log tangent scale on the Bygrave, for example, is
> over 20 feet long!
>
> I have been keeping a watch on ebay, but no examples of these slide rules
> seem to come up for auction, from which I conclude that they are pretty
> rare. If one did come up, it would fetch kilo-bucks for sure.
>
> Geoffrey Kolbe
>
> At 02:48 05/11/2006, Peter Fogg wrote:
>
>
> >Occasionally in the past cylindrical slide rules have been mentioned
> >here, eg; the one made by Bygrave.
> >http://www.quadibloc.com/math/sr03.htm
> >
> >I understand that this design was taken up and improved by a German
> >manufacturer, and that this German model (unsure of name) is perhaps
> >the finest cylindrical slide rule made.
> >
> >Does anyone know more about this? Does anyone possess one?
> >
> >


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