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Mechanically complete Sun / Moon rise set module; horizon shutter cams, movable dial plaques - October 2017


Buchanan writes: Today I prepared to start the cams. I needed a dial to work from for the shutter settings so I drew up a scale to print on paper. By the time I had drawn it up I realised that I was only one step away from engraving so I engraved it onto the dial plate. Just like they do on the front plate of a complicated watch movement.

Look at this engraving, it is beautiful and after the outer bezel is fitted will never be seen again! The readings around the rim will be used to gauge the accuracy of the cams as they are slowly filed until the readouts match the tables of when the sun rises and sets at the latitude of Chicago.


Buchanan writes:  I had to remake the collet that held the cams as I had an unacceptable wobble. I have removed the roller on a cam follower and replaced it with a mushroom head that is flat enough to pass the side of the cam. I am now in the process of scribing around the mushroom head every five days to obtain a rough idea of the cam shape. I have attached a long pointer to the edge of the shutter to read of the edge of the engraved dial plate.


That process involves the laborious iterations needed to refine the cam shape as the errors are eliminated by reading the result of each cam trim on the dial rim. This is the same process used to make the equation kidney cam. Both types of cams rotate once per year. There are 73 readings around the cam’s perimeter, each encompassing a five day period for a 365 day year. It takes ten to twelve entire sets of readings and trimmings to bring the cam’s shape to acceptable accuracy; so 73 x 12 = 876 individual readings. The second photo shows the rough outline of the cam following the initial scribe marks produced from the cam follower; the individual scribe lines are just barely visible. The table in the background is the sunrise and sunset times for the latitude of Chicago, Illinois which are used to correlate the readings on the engraved dial perimeter with the cam follower arm, and then each scribe is made on the face of the cam for each five-day period.


A cam in the vise being hand filed. One can see the individual readings as dots along the perimeter of the cam, second photo.


In this video the cams controlling the shutters are manually rotated through their one year cycle to show the extent of the day and night changes throughout the year.


Last month designs for the horizon cams were discussed. These are Buchanan’s renderings and I think once again he has delivered a beautiful and functional design. These two cams each control the sun rise, left hand shutter, and sunset, the right hand shutter. They will rotate once per year. So for the sunrise, why not use a depiction of the sun rising? Of course one could see the sun setting with the same design so the night sky was depicted, no confusion there!

The cams are now complete. Look, Mr. Sun has his own set of eyes as represented by the insertion of two small steel ball bearings! So this sun joins the one from last month in having eyes, one blue set and this one silver.


Our use of allegorical design has been used in cam work before. These three cams were made earlier, the equation of time cam, left, indicating sun time, was made with sun rays in October 2014 and the hour and quarter strike snail cams made in the image of a Nautilus shell cross section in January 2014.


The movable plaques that hover over the glass dial portion are fabricated, and next shown just before removal from the brass blank.


The first photo shows the very small size of these plaques, even smaller than the sunrise, sunset plaques. And this very small size demanded that block lettering be used as they are too small for script and due to the nature of the glass dial layout, could not be made larger. There is now a question of whether the mixture of script and block letter is a good one. An argument could be made for it all being in block, but then the script on the center-hub dial must be changed, and this looks quite nice as is. One could also say that block lettering is located outside the white enamel dial referring to the moon with script on the inside referring to the sun, and that is what we have settled on. Look at the style of these plaques, no simple flat engraved surface, but a raised picture framing edge, another in the many nice detailing touches.


Now starts the finishing of the shutter assemblies. So far the blue glass is still temporary plastic inserts.


The two steel pointers are now fitted to the sunrise, sunset plaques. Next the pointers positioned over the enamel dial.


The first photo shows the machining of the pair of dual steel pointers for the hours before and after moon rise and set. Next the pointers are blued.


All of the plaques that refer to the moon have block lettering are given a French silvered finish and are located outside the enamel dial. French silvering gives the finish a frosted surface and enhances legibility. All of the plaques referring to the sun are written in script on yellow brass, and are located inside the enamel dial, second photo.



The left illustration is the artwork for the glass dial that has the moonrise, moonset and angle hour information. The photo shows a plastic mockup with this illustration printed onto it and inserted into the dial bezel. The artwork will eventually be fed into a computer controlled laser for etching onto the rear of the glass dial


First a close up detail of the moon sphere opening for the glass dial. Next the dial mockup mounted to the mechanism with the moon located within the dial gap. Note the dual dial pointers now attached to the movable plaque to the right each reading a separate ring of numbers.

All of the dial components are now present. Only the transparent dial and the moon sphere are still mockups.

The main components of the sunrise/moonrise-set module. Parts count at about 550 is approximately that for the perpetual calendar. 


The sunrise/moonrise-set module is now mechanically complete.


In this video we demonstrate the module with both dials for this as well as the tellurian module below to give the viewer the full compliment of the complex wheel works beneath. The clear dial is still a plastic mockup and so has a bit of a wobble.

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