Finish mockup for perpetual calendar remontoire, begin calendar dial drive wheels - December 2014                     

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Here is the initial mockup for the subassembly that will contain a perpetual calendar module as well as the spring remontoire which will control the power feed of the remaining calendar functions. Shown are the main drive wheels. The mockup measures 8.25 x 4.5 x 2.75 inches (210 x 115 x 70 cm). The lowest wheel is driven by the celestial train and represents the last wheel in the clock at present in the calendar drive. This revolves 1/4 turn per day. It is geared 1:2 to the centre arbor. This arbor makes 1/2 rev per day and is the output arbor from the remontoire which is between the lowest and centre arbor. It will have a double arm. The ratio between the center arbor and upper arbor gives slightly more motion than is required to rotate the date hand from the 28th to the 1st."

These photos show the components of the spring remontoire which will feed power to the calendar mechanism once per day. The third photo shows the spring in its barrel.

The completed spring barrel gives torque in both directions. Next the barrel arbor is connected to a four pinned cam looking like a  lantern pinion as seen in the second photo. It has the pinion which acts to release and arrest the remontoire detent arm. That arm is shaped in a curvilinear pattern not just for looks but in case it should it become jammed against the cam, it has some ability to flex, thus avoiding damage. The third photo shows a pair of ratchet pawls behind the first of a pair of wheels to the left. One allows the wheel to only rotate in one direction while the other is involved with locking the wheel’s fly fan. Each wheel in the pair is designed to operate sequentially and independently of each other. One rotates clockwise and the other counterclockwise. Each is used to operate the perpetual calendar in either forward or reverse.


The perpetual calendar module which was fabricated last month is now mounted to the front of the calendar drive plates. The interior contains the calendar drive and remontoire. This is only a proof of concept model. The perpetual calendar module will later be placed in a location apart from the rest of the calendar drive mechanism.


Driving the perpetual calendar module.


These photos show a solution to the possible problem of the remontoire jamming. The remontoire releases at a certain inherent speed dictated by its drive spring and if one cranks the celestial demonstration function too quickly, it could overrun the remontoire’s speed causing a lockup or barring a clutch (which we will have) damage to the mechanism.

Our solution is if the rotation becomes too fast the mating lantern pinion to the remontoire detent arm will automatically retract, thus freeing up the detent. However, this is only one interesting feature of this contrivance. Should the remontoire arm become jammed for any reason the rotation of the remontoire spring barrel under the normal course of its being loaded by the celestial train will also cause the pinion to retract, thus freeing the jammed arm automatically. That arm is also specially shaped into an ‘S’ pattern to allow it to slightly flex should it become jammed up against the lantern detent pinion preventing damage to it and the pinion and allowing it to be freed up upon retraction.

In the first photo the arbor that has the cam attached to its end is shown in the retracted position, green arrow. A pin is attached perpendicular to this arbor and is shown by the red arrow. If the demonstration drive runs faster than the speed of the spring driving the remontoire, the pin will slide along the radial slanted groove pulling the pin backward and therefore the arbor inward. This will work in either direction. When there is no overdriving of the remontoire, the pin is at rest in the 12 o’clock position and the arbor is fully extended outward allowing the cam to fully engage with the detent arm, second photo. The video below shows this succinctly."

The remontoire safety device.



A front, rear and side view of the completed mockup for the perpetual calendar module and drive. Notice the two independent fly fan governors for the two independent bi-directional drives associated with the demonstration being able to be shown in forward and reverse. This model is approximately three times the size that the final module will be.

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

Merry Christmas, Happy New Year!


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.

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