Dear Tex, I also enjoyed the article on the Cycloid Polar sundial by Fred Sawyer. The dial as designed by Thys deVries of Prinsenbeek, Netherlands and published in Jul 1980 De Zonnewyzerkring, has a linear time scale that can be moved to correct for the longitude and equation of time.
I used the shareware program from NASS "Graphica" to produce a graph of the cycloid that produced a DXF file and I imported it into a CAD program (DeltaCAD - available at Walmart for $10). It was the only way I could make the curve at the time. The templates that Fred provided should also work fine. I understand Graphica is no longer supported and I am unaware of its status. I have a copy of the DXF file somewhere if it can be of any help to you. Just drop me email. I have discovered on the web a source of both a plotting program and a "Geometry" program at: <http://www.exeter.edu/~rparris> The author of the programs has made them available free of charge. I don't believe that either will produce DXF files but they do seem to be well written and run under Windows. I find the "geometry" program interesting because one can apply the geometry for making a sundial to creation of a geometry sketch and with one or two of the critical points being "drag" points -- make the sketch change for different latitudes or conditions. I have only begun to understand the geometry language of the program -- but I would challenge others to try it -- the dynamics of the visuals could be very stunning. I would not try drawing a cycloid yet -- but someday maybe. Good luck --Happy Dialing, Warren Thom (Lat=41.649N and Long=88.096W) Tex Brashear wrote: > Hello all. > > I found Fred Sawyer's excellent article on the cycloid polar sundial > in the December issue of Compendium to be a fascinating introduction to > this rarely seen type of dial. > The math required to solve the cycloidal gnomon was challenging, but > reasonable; and the proffered templates simplified the process of making > a sample pattern. > My question is this: Does anyone know of a graphical approach to > generating the necessary cycloid for the gnomon? If so, I would > appreciate the information. Sincere thanks in advance. > > Tex > Brashear
