Home-made sundial clock with Roman numerals

Sundials are typically associated with Classical Antiquity and for a good reason. They were widely used in Ancient Greece and Rome. The simplicity of their construction made them a lot more affordable than, for instance, clepsidras.  As a result, Roman numerals are still traditionally used on sundials. This particular one uses IV for 4, and not IIII as is often seen on mechanical clocks. I actually have encountered a book claiming that Ancient Romans never used IIII instead of IV, but clockmakers have somehow adopted this erroneous representation of number 4. Well, that is simply not true. At this time I am not going to provide any epigrapic evidence, but let me just mention that IV would have also been used as an abreviation for IVPITER, Jupiter. To avoid confusion it was quite reasonable to use IIII. I also believe that on a clock with 12 numbers IIII (And VIIII for 9, incidently) provides a better sense of progression of time (see Ucello's clock), because time is all about forward progress, while the more accepted variations of these numerals imply looking back and subtracting the first part of the compound numeral from the higher value of the second part. Well, you know what I mean. The sundial clock, however, is not capable of showing 12 hour time. It is possible that using classic forms for IIII and IV helps create a more balanced look. Anyway, here is how to make a sundial clock, as described by Archibald Williams in  Things Worth Making. Just remember that the present daylight savings time system has to be accounted for. Also, I would suggest picking a sundial motto, as it is quite customary in the business of sundial making.

A HOME-MADE SUNDIAL

 

A sundial is an interesting thing to have on a garden wall or the stump of a tree, or to set in a south-facing window. Ordinary flat and vertical sundials require the use of advanced mathematics; but that to be described is within the capacity of any handy person.

 

One begins by making a cross of thin metal. Brass, copper, zinc are all suitable; copper is the best. The cross may either be cut in one piece out of the sheet, or be compounded of a vertical piece and a cross piece riveted together at the point of crossing. The dimensions given in Fig. 44, a, are for a small dial, but they may be modified to suit individual fancy, provided that the circumferential length of the cross-piece B be the same as the distance between the centres of the holes in A. Mark off the cross-piece into twelve equal parts, and subdivide each of these into quarters or twelfths. The lines may be scratched or etched with acid. For the hours use the Roman numerals, which, being made up of straight lines, are very easily engraved.

When this has been done, bend both pieces to a truly semicircular shape. To get the curve correct one must cut out a cardboard circle with half its circumference equal to the length of the crosspiece piece and use it as a template. The exact diameter can best be arrived at experimentally. If copper or brass be used, anneal it by red-heating and plunging into cold water before it is bent.

 

As the pieces are easily distorted, if of thin metal, it is advisable to solder to the back of each a rib of the same metal, cut out with the aid of the template already made. One rib will have to be severed at the crossing-point to give room to the other rib, to which it should be soldered. If stout strip metal be used, this backing will be unnecessary, but in this case a wooden template had better be cut to the right curve to enable the shaping to be done accurately by hammering. After shaping, slip a piece of quite straight copper wire through the holes in A, and make them fast with solder.

 

The dial is now fixed facing the south (in our northern latitudes), with the wire sloping towards the north, and making with the horizontal an angle approximately equal to the latitude of the place --for London, about 51 1/2  degrees. To state the matter otherwise, the axis of the wire should point to the Pole Star. The orientation must be established accurately by a compass.

The dial is most easily fixed by means of a little wooden saddle crossing A, with a screw at each end penetrating either a horizontal base board (as shown) or the face of a wall -- in which case the saddle would occupy the position indicated by the dotted lines.

When consulting the dial at any time, add or subtract the noon difference for the day from the shadow reading to arrive at clock time. At most the noon difference is only about a quarter of an hour.