Bygrave Position Line Calculator
The Bygrave Calculator was developed for celestial navigation, and the scale set on this calculator are still being used today. From what I can observe on the internet, the scales have been replicated, but few people are attempting to duplicate the original model, which is a shame. This is a beautiful instrument.
If you are new to this SR, I recommend you first read the excellent paper by Ronald W.M Van Riet.
www.rechenschieber.org/PositionLineSlideRules.pdf
This project came about when I was working with Francis Upchurch on his Fuller slide rule project, mid 2009. Francis had an original Bygrave - I understand them to be extremely rare.
At that time he was trying to replicate the scales so that he could use them while sailing, and keep the original safe at home. When I saw photos of his Bygrave, I knew I had to try to replicate it as a facsimile. It's a complex looking instrument, very elegant. Dimensionally it's quite small, meant to be hand held.
Francis' original Bygrave (Left), and home built (Right)
Thanks to Francis' generous support with photos and reviewing the scales I was able to build a pretty fair copy with cardboard tubes. Francis also built his own copy, and used it while sailing of the North sea (backed by GPS). He reported it as a reliable calculator.
Wayne's prototype
The replica required that I create a lot of custom fonts. Like most such instruments the scales were hand lettered. The Bygrave was exceptional in the number of completely different lettering styles in play. These were very pretty, but tricky to duplicate.
The files provided are PDF (which is often hard to re scale with software at home). If you are interested in building this yourself, contact me at my email address. I've built the PostScript pages to be scaleable, so any materials with sizes close to the original Bygrave dimensions can be used.
BygraveOuterv1.PDFBygraveInnerv1.pdfByGraveMiddleV1.pdf