Dear David and Alberto, 1. LOVE your father's dial. Very nice.
2. There was an article in Scientific American some years back in "The Amatuer Scientist" section on dials with EoT gnomons. As I am several thousand kilometres from my office, I can't easily locate the reference for you. BTW, there has been a few articles on dials in this section of Scientific American on dials. Again, memory is poor, but one involved polarising films, and another included a curved gear rack for adjusting for longitude (???). I have always been intrigued as to how you actually make a curved rack with the properly formed teeth on the inside. It is a far from trivial machining exercise. You can't just make a rack (or buy one) amd bend it as this destroys the spacing of the teeth. And in any event, the gears on a rack include BOTH the teeth AND the spaces. Anyone got any suggestions on how to make such a rack? In case you can't visualise it, imagine a U-shape with a semi-circle forming the base of the U, and two parallel arms coming out. What you need is a properly formed set of teeth on the inside. I guess you use a shaper, but I only have access to a mill. Cheers from sunny Alice Springs, where the sun (almost!) always shines, BUT there seem to be no public dials! I guess that says something about Australian culture! John Dr John Pickard Senior Lecturer (Environmental Planning) Graduate School of the Environment Macquarie University NSW 2109 Australia Sabbatical leave July - December 1998. You can't contact me by phone or fax as I am on sabbatical leave in arid and semi-arid Australia. Please contact me via email or post material to the above address. It will be forwarded regularly.
