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Begin dial bezel work; begin debugging and finishing of calendar module - June, July 2020

In this installment Buchanan begins to make the bezels for the multitude of dials on the clock. At the same time the calendar module is disassembled and the difficult job of debugging and then finishing begins. The calendar module is possibly the most challenging to have constructed and debug. Although it has about the same number of parts as the tellurian and Sun/Moon rise-set modules, it's design is completely novel and shares little in configuration or fabrication with conventional clockwork mechanisms.

The first thing that must be done before beginning the bezel work is to take an inventory of the dials. These are only the main enamel dial works. There are many subsidiary and adjustment dials that are made of engraved brass and then finished by a French silvering process to give the surfaces a silver, crystalline look something akin to snow.

The entire master artwork for the dials was done by Buchanan and the dials fabricated in China through Bob Crowder's ProClocks company. Bob's personnel produced a product that was perfect for our project. This effort began in February 2008 through June 2013. During this time some changes were made and dials re-ordered. There are photos of the dials being created and the artists who created them in a four-part series here: Part 1, Part 2, Part 3, and Part 4. In November of 2018 we ordered a replacement orrery dial to add color to the zodiacal figures to better coordinate with the tellurian dial. This was the third design revision to this dial and can be seen here.

Below are the polychromatic dials. The multicolored figures and scenes required several firings as each color must be applied and fired separately. There is always the risk of a dial cracking or warping at the red-hot temperatures of the kiln, and this is made even more difficult when making a dial ring as opposed to a solid dial disk.

Tellurion dial, 6", (15cm)

Orrery dial, 11.5" (29cm) in diameter.

Planisphere dial. This was the most difficult to produce. The star fields and milky way required thousands of dots, and the zodiacal names were all done in a calligraphic font. The multicolored scene required several firings as each color must be applied and fired separately. The blue gradation from light in the center to dark as it approaches the perimeter required special skills to mix the paint in differing quantity as the artist moves from center to edge. One must remember that the color of the enamel that the artist sees out of the bottle is not the color that is revealed after hours in the kiln. So he must be able to know exactly how the mixture will look even though he cannot see it when applying it. One might wonder why the zodiac figures are of the same color when they are much more complexly colored in the tellurion and orrery dials, the answer is that the dark blue background precluded this.

Monochromatic dials.


First photo: names for the moon anomalies, pull-repeat button (2), winding duration (4), pendulum beat plates (2). Second photo: Twenty-four hour dial, thermometer, equation setting calendar, strike control.


First photo: day of week, date, leap year. Second photo: Mean time and separate sidereal hour and minutes nested dial set. These dials presented some difficulties as to fit, see below; the outer mean time dial is stationary while the inner two dials rotate counterclockwise to the sidereal hours and minutes. One dial has been left off, we will see it later in this installment.



In the four photos above, Buchanan has made a stepped gauge from Corian to measure the dial's perimeters and allow for the metal bezels needed to fit between them. Each dial must be able to comfortably fit around the gauge. There were some problems in the fit and Buchanan had to do some very careful grinding around the perimeters of the fragile and brittle enamel dials to get them right. Here there are three dials that must nest perfectly and allow for the thin brass bezels between. I had always had some reservations about this especially since over the years the outer main dial had been remade and the actual enamel dials for the sidereal minutes and hours since being completed in May 2013 were never all mated together between the three dials until now. But in the end they were all made to fit perfectly.


The bezel blanks after being stress-relieved. This is a procedure through which the brass blanks are first put into a furnace to heat the metal removing whatever stresses may have still been present from the casting and rolling operations performed at the the foundry. This process is used whenever there will be a final part that is machined into a rather long, thin part. For example, the base frame members are long in comparison their cross sections and were all heat treated, here the blanks are machined into thin bezels. If the metal is not stress-relieved, the thin fabrications may begin to curl as it is machined.

Buchanan writes: I have the Tellurian and Calendar dial turned.  I have thickened them slightly to surround the outside of the mechanism front frame. A very nice idea, another special touch that makes the overall presentation so special.


The slightly resized dials required a new pair of sidereal mounting rings, left photo, the beginnings of the bezel ring of the mean time dial, right.


Here Buchanan uses tooling to create the bezel rings decorative profile by hand, next the completed ring before removal from the lathe head. See video below.



The completed outer and inner bezels for the mean solar time dial. Later the entire set of bezels will be plated in gold.


The build up of the sidereal dials, the inner dial for the minutes, left and the outer for the hours, right.

The complete buildup of the three dials, composing the mean solar time and sidereal dials. The equation of time will also be read off the mean time dial.


To give the illusion that each dial has an inner and outer bezel, the outermost mean time dial has the standard thicker, milled outer bezel and thin inner bezel. The two inner dial rings each have a thin bezel on their inner rims only but when installed share the next dial’s inner ring to give the impression that they too have a bezel on their outer perimeters. When done properly it looks better than if one tried to give each ring a full set, as it would look too thick. This design retains a delicacy and is necessary as the enamel dials are too close a fit to do independent dial rim pairs. Notice in the first photo how Buchanan achieved a nice, flat surface alignment with the multiple dials.


Video demonstration of the completed nested dial set for the mean time, and sidereal time. Notice the fine tolerances between the dials. Another thing to notice is how nearly perfectly circular they must be to pull off this effect. This could only be obtained by Buchanan's additional grinding work on the dial perimeters and accurately applied bezel rims, something that is usually not necessary in a standard, stationary dial application.


The tellurion dial with its inner and outer bezels.

Look carefully at the picture to the right. There are several areas where frames must be countersunk behind the dial bezel. Here there are two curvilinear arms which are just barely apart from each other as they pass the perimeter of the bezel rim, but instead of taking the easy way of making one opening for both frame arms, the tiny area between them is left intact resulting in two openings that fit the pair perfectly.

The photo above shows another example of countersunk frames.

The upper calendar bezel is now complete, below the three dial mounting plates for the mean solar and sidereal time dials..


Buchanan writes: I managed to fit the sun moon plaques onto the Bezel. I put a curved bend onto the plaques so that they match more nearly the profile of the bezel and I think it is a good improvement. I made a curved former and pressed the plaque into the bend with a rubber block. I had to increase the curve a few times to counteract the spring back but in the end they were pretty good. I also had to carve the corners of the pockets square by hand to fit the square corners of the plaques.

The plaques fitted into the Sun/Moon rise-set bezel rim.

The bezels are now complete for the calendar work. The dial to the right, the month and seasons is being remade now to correct for the Summer and Winter upside down lettering.

Dials and outer bezel mounted to calendar frame.

Calendar frame mounted to clock. Note the close fit between upper semi-circular bezel and the lower circular bezel.


Buchanan now turns toward the debugging and finishing of the perpetual, third-order, reversible calendar module.


In this video Buchanan disassembles the calendar module.                                                                        

Partial calendar module de-bugging list
1       Pin trip cross lever
2       Pin S trip lever
3       Fix / clamp reader lever springs
4       Shorten date lever.  
5       Stop on date trip lever 
6       End shake control on 400 year cam assembly.
7       Fix year counter detent bearing 
8       End play on leap year main arbour   
9       Straighten date trip coil spring, will be done in the assembled calendar
10    Pin year counter in feed bevel to arbour.
11    Adjust year counter.
12    Replace clear jewels with Red jewels to be done after testing and polishing. Half done
13    Pin cams to cam shaft.  9 pins. 
14    Spring drags on all dial arbours
15    Pin balance weight. 
16  Missing screw in 4 year cam

These are the parts of the calendar trip mechanism, it is what drives the module’s computational cycle once daily and is a sub module of the calendar mechanism.


These three photos are of the drive and logic cam components of the calendar trip mechanism. The first photo shows the timing camshaft (logic cams). This is the coordinating component of the system and synchronizes the movements of the various levers that move the other parts of the calendar. It rotates one-half turn per cycle and its rotation is driven by the spiral spring.  It acts as the ‘clock’ found in mechanical analog computers to time the rest of the components in the computer. The fly blades in the first photo are part of a governor to control the spring release.


Various wheels and their build-up.

Month index wheel, left and day of week index wheel, right.


These two photos show the month and day of the week indexing wheels. Again one can only marvel at the delicacy, artistry and craftsmanship that it takes to create these parts. All the more so when one realizes that the same function could have been accomplished with a tenth of the effort using conventional designs.


These three photos show the year trip function linkage and is one of the more complex lever assemblies in the calendar and provides the output to digital display for the year.

The year trip linkage is shown here just before the assembly of the calendar module in July of 2015. There are three layers of linkages each subsequent layer relying on information from the former, their order is: Day/Date, Month and Year. This photo shows the year linkage and how it operates as an analog computer component, in this case a dual AND gate.

This photo shows the various components that connect to this linkage. Notice the logic cams in the lower left hand corner. It is the component that was shown earlier in this installment with the calendar trip mechanism. The year linkage receives input from all the components in the calendar that will decide when the next year is to be displayed. In a perpetual calendar that condition follows rules to keep the man-made calendar in step with the seasons as time passes. That means adjustments need to be introduced and the first is the leap year every four years, (a first-order perpetual calendar), then the cancellation of the leap year once every 100 years, (second-order), and the re-introduction of that adjustment every 400 years, (third-order). To accomplish this the calendar must become a simple analog computer. To do these calculations in forward and reverse the calendar has the four components needed to qualify as a computer: Input, Processing, Output and Storage. When one hears of a clock having a perpetual calendar function it means that it is only of a first-order capability.

How could anyone looking at these parts think that they are part of a clock?


The calendar frames are now finished.

Parts count to date: 5309

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