Hello Roger, You wrote : > My suggestion to calculate the hour lines is to treat the cylinder like a > polygon with a series of flat vertical faces. Calculate the lines for each > face the usual way as a series of vertical declining dials. Lay out the > design for each facet and draw a smooth curve through the mid points for > each face to approximate the hour angles.
Because a cylinder can be described mathematically it is rather easy to calculate all the wanted points for a dial on the outside of a cylinder. The cylinder also can be unfolded to a flat plane so a drawing can be made. It depends on the dimensions of the tower and the length of the gnomon what the result will be. In the picture you see such a dial on a vertical cylinder with radius 250 units with a perpendicular gnomon of 25 units, pointing south, for latitude 45 degrees, reading local suntime. The hourlines are curves, not straight. Best wishes, Fer. Fer J. de Vries [EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat. 51:30 N long. 5:30 E Attachment converted: Macintosh HD:cyl1.gif (TIFF/JVWR) (0000FFAF)
