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Finish perpetual calendar. Begin tellurion assembly - July 2015

This month we finish up the few remaining details to complete the perpetual calendar before moving on to the tellurion.



These photos show some of the final fabrication stages for the calendar module. The wheel cocks and movement pillars are cut and decorated. Next the pillars which show as plain rods in the first two photos are now turned with decorative ends and a central knop.


A few more small housekeeping chores. Here Buchanan installs the manual adjustment knob for the digital year counter. The circled area shows the connecting rod from the knurl knob to a gear that adjusts the counter. Note the small decorative spur on the frame as well as the pillar opposite aligns perfectly to allow that long rod to connect to the counter and be supported on the opposite end. This demonstrates one of the hundreds of micro planning decisions needed to make this machine work well. That small spur on the counter frame had to be pre-planned and the area where the pillar is planted free from obstruction well before the adjustment assembly was made.


The first photo shows a close up of the adjustment knob. Next the tiny knob being turned. The center counter-rotating dial below within the main time dial is still a paper mockup and has become somewhat soiled while the remaining dial work is in the final enamel material.


These photos show the tiny manual adjust lever for the leap year dial now made and in position.



The first three photos show the fabrication of the manual ‘finger levers’ that the operator uses to disengage the individual detents for each dial readout, thus allowing for their adjustment. The fourth photo shows a tiny stop lever which is fitted to each of the detents, circled area. These will prevent the levers from flopping out of position in the event the calendar module is removed and turned upside down. In this manner everything stays in place preventing accidental derangement in repair or the reassembly which will be necessary when the machine is shipped from Australia to the United States.

Below are a series of photos showing the internal structure of the calendar assembly. For a description of the calendar calculator module's structure see the October 2014 and February 2015 installments.

The first pair of photos encompasses two dials of the calendar assembly. These are the day and date readouts. The day readout is the simplest of the calendar. Monday through Sunday is a seven day cycle that remains constant throughout the year regardless of the other complications to account for the variances in February or the leap year cycles. The date is an entirely different matter and the date readout is connected to the calendar calculator module that determines the number of days February should have in any given year. This module accounts for not only the quadrennial leap year, but the 100 and 400 year exceptions to the February rule; making this a third-order calculator that is good in perpetuity. It is also fully reversible. So any of the calculations needed to keep the calendar accurate going forward is remembered after the calculator is run in reverse. This was not an easy task.


The next pair of photos shows the month calculation. The month trip is controlled by the calculator module so February is tripped at the right time according to the perpetual rules. The circled area is the detection detent for the month. This is tripped on a regular basis but for February the number of days is determined by the calculator.

The third set of photos concerns the leap year dial and the year counter. The year calculation is the most complex since it is dependent on the date and month calculations as determined by the calendar calculator and the month readouts as well as the quadrennial leap year.

From these examples one can see the hierarchy in the complexity for determining the calendar readouts. The simplest is the day, unvarying throughout the year, there are no adjustments here. Next is the date which is inextricably connected to the February cycle and requires the use of the calendar calculator module. Next is the leap year which is determined by the calculator module to give it perpetuity. And finally the year counter which only will turn over after all of the prior conditions for the signal of the year is given based on all of the prior data sets being met.

Below are a set of photos of the completed perpetual calendar assembly. This complication is expected to be one of the more challenging of the project. Total parts count exceeds 580.



The video shows the perpetual calendar. This is a completely self-contained unit encompassing over 580 parts. The calendar is a third-order variety, taking into account leap years as well as the 100 year and 400 year exceptions to that cycle making this perpetual in perpetuity. The machine remembers the calculations needed for this ability in both forward and reverse. We believe this reversibility has never been done before in a the context of a mechanical timekeeper.


Now begins the fabrication of the tellurion complication

The model we are using for the tellurion was made by Mathias Hahn and is described in Astronomische Uhren und Welt-Modelle der Preistermechniker im 18. Jahrhundert, Luwig Oechslin. This is a two volume set of German-language books that contain the descriptions of many of the world’s famous astronomical clocks and orrerys located in Germany. There were several examples of Hahn’s work. The most important part of this publication is the attached set of folios that show the schematics of each item described. We chose a hand-cranked telluriom as well as a grand orrery, both by Hahn for our components. The tellurion dates from 1780 and is in the Lindengut Museum, Winterthur, Germany. This saved countless hours of design time if we had to design these from scratch and is another example of our borrowing what we consider to be good ideas from the past masters in the horological field. These were chosen at the earliest stages of the project, even before the original wood mockup was created in 2006.

On the drafting board Buchanan begins the preliminary design work. The photo on the upper left hand corner is a photo of the Hahn tellurion from the German language book. The schematic to this tellurion is in the right hand corner and comes from the same source. The center drawing is Buchanan's interpretation of this and the large diagram below is the initial scale fabrication diagram.


The photo and two diagrams are what is seen on the drafting board. Note that we have added to Hahn's design by including the inner planets of Mercury and Venus. Buchanan states "This is the first version of the tellurion, my interpretation of the Hahn to understand it and to see if we could include Mercury and Venus. I took the Pouvillon ratios from his tellurion. Now I must see if it is physically possible". Here Buchanan draws from his experience in the restoration of the Pouvillon astronomical clock he had accomplished in 2012. Pouvillon's interpretation of his tellurian was magnificent.


The first drawing shows diagrammatically all of the necessary components to get an idea of how deep this assembly must be. It shows that the Earth will be about 1/8 inch (less than 0.5 cm from the front case glass. This is a bit too close, but Buchanan indicated that the glass case can be moved forward a bit. The issue we have is not so much that we cannot make the case deeper, but that we do not want the front surface of the glass too far in front of the rest of the clock mechanism; making close inspection of the remaining movement more difficult. The second photo shows an initial trial for the fitting of the tellurion within the existing dial work. The Earth, Moon system will overhang the dial ring as shown in the twelve o'clock position. just below are a set of large idler wheels. Here we have options for changes in their diameter. These are the largest size possible and were deemed too large and out of proportion. There was also the consideration that behind this mechanism is a portion of the curvilinear lever works of the strike/repeat system, which we would not want to obscure unnecessarily.


The first drawing shows the over-sized idler wheels. Next several alternative sizes superimposed. This also has a side elevation represented above.

The revised idler wheels are now finalized and this gives the tellurium a slimmer profile.


The first drawing depicts the central cannon tube nest. Notice the use of ball bearings which replace the conventional nested cannon tubes. One must remember that this assembly in reality is rotated ninety degrees from the drawing shown. If a conventional set of nested tubes were to be employed here, the friction would be impossible to overcome. Here is a good example of where modern design and materials make possible what would otherwise be impractical. Next color coding is added to the diagramed tellurium wheel assembly. This has been carried through the previous few drawings as well. Red = Mercury, Yellow = Venus, Green = Earth, Black = Moon, Blue = main input drive to tellurium. Not all color coded wheels of a particular color are all adjacent to each other, but may be located elsewhere and working through other wheels to their final destination.


The wheel blanks are now ready for fabrication. If we were using modern CNC methods the data on the sheet would have been inputted into a computer and the wheels automatically cut out. But here Deryck scribes out each wheel by hand, as was done for centuries by the old masters of horology and will cut them out each by hand on the jeweler’s piercing saw in the same hand-made manner as hundreds of wheels before in this project.


The wheel blanks are attached to the appropriate sized lathe collets and then inserted into the lathe head. First the blank is turned on the lathe to produce the exact diameter. Then the blank is rotated by one tooth per cut using an indexing servo. The second photo shows the first tooth being cut.

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