John Pickard wrote:
>
> 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.
Hello All,
I was able to track down the above mentioned SciAm article that
describes an Equatorial Dial incorporated with a rack and pinion EoT
adjustment mechanism. It appeared in the Amateur Scientist section of
Scientific American, 1967 Nov, pg 131. The adjustment mechanism also
servered to offset the time differnce between the users meridian and the
standard TZ meridian.
Regards,
Luke Coletti
