Hi dialers! In reference to the ring dial instructions given by Emerson:
How wide should the ring be? No specific mention is made in the instructions. Measuring the drawing in the book gives a ring diameter of 40mm and a width of 11mm. This is roughly a 4/1 ratio. I can see that the narrower the width becomes, the more severely slanted the hour lines will be, and therefore, more difficult to read. I can also see that if the width is too wide, the spot of light will droop at either edge of the ring making the altitude of the sun to appear higher than it actually is. Does anyone have any opinion as to what the ideal "diameter to width" ration should be? Also, as to the thickness of the ring: Obviously a thicker ring will be more likely to hold a circular shape, but if the hole that passes the light is on the outer surface of the ring and the hour lines are on the inside, would this not then introduce an error? Emerson's diagram indicates the inner and outer diameters to be the same. Perhaps in reality, the dial should be designed with the altitude angles measured from an outer hole but marked on inside hour lines. Any thoughts on the effects of ring thickness? Regarding physical construction: I plan to make a simple paper version of this dial just for fun, but if it works well, I'd like to make a permanent one out of brass. Does anyone have any idea how to form a flat strip of brass into a perfectly circular ring without damaging the engraving on either side of the strip of brass? Also, what alternate methods of mounting the "hole" can anyone think of other that a thin strip of brass riding in a channel that circles the entire ring. The reason I ask this is because I'd like to have the bottom outer surface of the ring available to engrave the equation of time on. How about adjustment for latitude? I can't see any reason the attachment point for the thread at the top of the ring couldn't be made to slide back and forth for latitude adjustments. However for a double holed dial such as this one, the latitude adjustments would have to be adjustable in two directions, one for each half of the year. Charles
