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Re: Bygrave position line slide rule
From: Dan Allen
Date: 2004 Feb 28, 20:48 -0800

Zvi Doron wrote on Saturday, February 28, 2004 8:02 AM: Henry Hughes & Son of London, England used to make a cylindrical 3 part position line slide rule for astro navigationsometims called "Bygrave" that worked on the principal of solving two right angle triangels instea of the complete PZX in one calculation. Francis Chichester used one on his epic solo flight across the Tasman Sea (1931) and Weems in his book "Air Navigation - British Empire Edition" gives a drawing and a few details. I could not find any reference to it on the web. Has anyone - ever used one? got one? seen one? knows if they can be had and for how much? Any information will be gratefuly received. --- I found one thing from Google: http://home.ecn.ab.ca/~jsavard/other/sr03.htm The Otis King Slide Rule This slide rule consists of a body with a helical scale, on which a sleeve with a similar helical scale could both slide and rotate. An outer sleeve then slid and rotated on that sleeve at one end, and at the other end was constricted to slide directly on the body. Marks at the two ends of that sleeve constituted the cursor of the slide rule; thus, instead of placing the two helical scales in coincidence, points on the two scales separated by the distance between the two cursor marks were treated as corresponding. The Otis King cylindrical slide rule was perhaps the most popular and inexpensive circular slide rule made. A special-purpose cylindrical slide rule made for use in sight reduction for celestial navigation, the Bygrave position-line slide rule, was based on the same principle. --- As a mathematician, I simply turned your problem into a different one: what the heck is an Otis King slide rule? Sounds very interesting! Dan

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