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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.

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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.

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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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