Demonstration of the calendar drive

This drawing shows a bit of what was described above concerning the layout the calendar mechanism. Here the perpetual module has been separated from the remontoire, calendar and the input drives.

Here we have a front and side elevation drawing of the bezel and dial cluster. Next a log of the wheels needed for the perpetual module and drive works. The dark box contains the various cutters that will be used to create the various tooth profiles needed. So far there are twenty one wheels, excluding those needed for the actual dial indicators.

Now begins the fabrication of the calendar in metal. First the rough wheel blanks cut directly from the sheet brass are stacked up like a set of old coins. Next one of the cutters used to cut the teeth and next the completed set of toothed wheels before spoking out. The scale is 1.5 inches or 4.0 cm.

Next one of the brass blanks upon which the calendar system will be mounted is installed. The last time the clock had large brass plates on its structure was in January of 2011, but a good photo of this is December of 2010. The plate has two aligning pins that fit into  two blind holes in the pillar behind the plate. An elegant knurl knob and decorated shaft will hold the calendar module to the rest of the movement, second photo. The knob is positioned away from the wheelwork that is directly below to avoid injury to those parts when manipulated. Removing this one retaining fastener will release the entire calendar assembly from the rest of the movement. We will replicate this type of modularity with the rest of the major complications.

Here Buchanan begins to make a contrate wheel, next the beginnings of another complex-shaped potence. The last photo shows the completed contrate wheel and rough potence for the calendar drive.

Here we see how Buchanan uses a jig to transform the rough potence into the contours of a complex part. The outside diameters of the hard steel tubes, also sometimes called filing buttons, supply the pattern for the softer brass material. Hand filing then can create a near perfectly round profile using the tubes as a guide.

The completed lower pivot for the calendar drive. Later the contrate wheel will later be spoked out.

Here we see Buchanan fabricating the upper pivot for the drive to the calendar. I included this to show that this part which is an angular shaped part is actually cut from a piece of brass rod stock rather than what one might expect, a bar stock.

The completed, but as yet not yet embellished upper pivot showing the angular shape. The second photo shows the intersection of the sidereal and calendar drive arbors. The calendar drive is now in place.

Now begins the fabrication of the calendar module. The first photo shows some of the arbors that the wheels which the individual calendar dial hands are be attached will be mounted. These arbors are attached at only one end and are called dumb arbors. This is  necessary as the free ends of the arbors are located in the center of each dial ring. The drive illustrated in the previous photos is shown.

The first photo shows how these dumb arbors are arranged in the middle if each dial. Next a side view. Notice the large amount of space between the dial drive wheel and the dial. This is necessary because the perpetual calendar module will be located right behind the uppermost dial in the dial cluster.  

These two photos show how the entire calendar mechanism will be positioned within the machine. It nicely fills in what otherwise was a rare piece of open space. The front plate holds the dial drives and perpetual module. The rear of the front plate as well as the rear plate behind contains the balance of the calendar mechanism; the remontoire, fly governors and associated, reversible drive gearing. It is Christmas time and Buchanan has put on a pair of Santa hats on the two pendulum balls. See video below

Here the wheels undergo a depthing operation. Once the optimal depth of each wheel is determined those measurements are transferred onto the brass plate where the wheel arbors will be planted. The third photo shows a view through a microscope where the intersection of the two scribe lines marks where the plate needs to be drilled. 

These two photos show a new set of screws that needed to be made for the smaller wheels. These wheels are the smallest yet made in this project. The matchstick is just over 1.5”, (4 cm) long and the diameter of the screw head in 30 thousands of an inch in diameter.

Here the wheel collets are threaded using a small tap. The scale is small enough that it is turned by hand by the knob located above the jig.

At this scale it was decided that the cheese head style of screws were not appropriate and were changed to a countersunk oval head type. The first photo shows two loose cheese head screws to the left, with one of the new style screws installed on the wheel. The match head gives an idea of how small a scale we have started to employ. Parts of the calendar work, the perpetual module in particular, as well as parts of other complications will be on the scale of pocket watch work. This will be most evident in the orrery.

The completed wheel works for the calendar dials are shown both in pieces and assembled. There are 46 parts that comprise this subassembly.

The first photo shows the spoke scribing jig Deryck uses to correctly divide the number of spokes to be cut. The wheel being spoked is just over 0.5” (1.5 cm) in diameter. Even such small wheels are spoked out, no short cuts.

 The oval head screws look good on the finished wheel, next a few completed wheels.

These photos show the difference in weight from the wheel blank at 19.3 grams to the spoked out wheel at 3.2 grams. This is an 83.4% reduction and a testament to Buchanan’s fine wheel rim and spoking.