Complete tellurion assembly, and sidereal dial drives - February 2016
This month we finish the tellurion and complete the dual sidereal
time chapter ring drives.
In the first photo one can see a thin dished washer inserted between the
wheel and a screw-down collet. This acts as a slip clutch for the the
seasons indication. One of scores of clutches used throughout the machine
for safety as well as setting functions for various components and
The last part needed to complete the tellurion is the quick-release
lever which will allow the operator to easily remove and reinstate the
entire assembly within the rest of the machine. We use the same design
philosophy for the calendar complication. The modularity aids both in servicing as
well as safety in the transportation of the clock when it becomes necessary.
The first photo shows a paper inserted into the area where the lever will be
located. Here areas where the lever cannot go are outlined, thereby giving
Buchanan an idea of the shape and scale of the lever that will be allowed
within this area. As the overall movement becomes more and more crowded,
this exercise becomes ever more critical and difficult.
Next the areas are transferred to the brass blank and last a rough outline
for the lever is drawn.
The first photo shows parts for the spring loaded locking pin. The lever is tested for fit on the tellurian test stand.
The completed locking knob and pin as well as it mounted to the lever are seen in the
first two photos. The steel arbor is where the tellurian assembly is
mounted. Next the quick release lever is in place on the strike train frame
pillar, circled area.
Now Buchanan takes the entire tellurian apart to complete the jewelling
of the pivots and the semi final finishing of the frames. This process will
be repeated at least once again in the final frame finish, screw bluing and
After all the pivot holes are planted the jewel holes
are prepared. FirstBuchanan centers on the
pivot hole with a microscope, then drills the hole out undersize, then bores
out the hole with a boring head as seen in the first
photo, then reams
the hole to size in a staking tool. Repeat 29 times
for all jewels.
Then the frames are finish filed. Everything loses
a little more weight.With so many
components, the slimmer each part can be, from a visual perspective, the
The first photo shows the 13 pillars used for the
tellurion triple frame assembly. Next the two main frames ready for
The nineteen jewels are now in place within the four frames and one cock.
Next the triple frame design is readily seen from the side view.
The organic ivy design found throughout the movement is continued here
within this subassembly.
The bare frame shown in the prior photo is now filled out with the
compliment of components for the entire complication. The celestial bodies
are still mock ups and will later be replaced by Mammoth ivory and
The tellurion is now complete and installed within the context of the rest of
the movement. Is all this this looking a bit complex yet? Total parts count
on this complication comes to 395.
Each turn of the demonstration crank equals one day. Total turns are ten.
One can just see the movement of the tellurion armature counterclockwise as
well as the rotation of the Earth and Moon's orbit. Although it is not clear
in this clip, the calendar is also advancing at the same time.
We now move on to complete the sidereal time dual rotating chapter
We now turn to the completion of the sidereal time
indication. Here I will recap the process by which we created this function.
The original design envisioned in July 2006 was to have a separate, small
dial for this. It would have been delineated in the conventional twenty four
hour format. In September of 2013 I attended a symposium where a Thomas
Tompion clock was displayed that showed sidereal time on a stationary dial
with mean solar time as a clockwise rotating chapter ring concentric around
the stationary sidereal dial ring. This allowed one to read both times
simultaneously with only subtracting twelve hours from the sidereal time
reading after midyear of June 30 to convert to the twenty four hour format
since the sidereal dial was delineated in a twelve hour format. This is
necessary as the hour and minute hands are geared to rotate in a
conventional twelve hour format. Since we had already created the dial and
mechanism for the mean solar time, and this is a more important function in
our design than sidereal time, we chose to have the rotating dial for the
sidereal time which would be rotating in a counterclockwise direction. We
had assumed that we would be able to use both the hour minute and second
hands to read off both dials simultaneously and created the inner rotating
dial and all seemed well. However, after studying this I came to the
realization that this arrangement would only work with the hour hand, not the
minute or seconds. To enable a more accurate reading there must be a
separate counter rotating rings for the minutes and seconds.
So a decision had to be made. Do we go with the
arrangement as made allowing a reading to the nearest five minutes or so
using just the hour hand, or do we go with additional rotating rings or dial
hands geared to sidereal time? It immediately became apparent that three
additional hands would be prohibitively expensive. We would have to create
an additional three cannon pinions within what already was a set of four
nested cannon pinions (hour, minute, second and equation). Since this was
not anticipated when these were made, the seconds would be the diameter of
medical hypodermic needle. Not only that, but the dial would have been
cluttered with seven hands. However, one additional ring for the minutes was
practical. An additional seconds ring was ruled out since it would have made
the entire dial structure with four nested chapter rings too thick; nearly
obliterating the open center section and throwing the entire sense of visual
symmetry off balance between the left and right main dials. The following is
Buchanan's beautiful solution to the problem, a classic case of ‘making
lemonade out of lemons’.
Buchanan’s solution was
to create a rotating cage driven by the current sidereal hour and within
this cage are three rollers which support a central hub. That hub is driven
separately to display sidereal minutes.
The parts begin to be
made. Notice the number 240 and 256 in red on each toothed disc. These are
the number of teeth cut into each rim. Next the rollers and roller cage
begin to be fabricated.
These photos show how
the cage rollers are mounted. Each of the three roller’s arbors are attached
at one end with a countersunk foot that is then secured by a screw, red
The carriage is
beginning to take shape. Notice the jewelling on the rollers supporting the
Now begins the spoking out process. The first photo shows the jig
Buchanan uses to accurately scribe out spokes. The center steel rule has
an adjustment screw on both ends so as to accurately have the edge perfectly
bisect the center pin. The pins arranged around the outer perimeter allow
Buchanan to select any number of spoke combinations from three to six and
more. Next is a large and amazingly delicate 256 toothed wheel showing a
completely missing center section. This will later hold the rear roller cage
Now the artistic aspect
begins; the fun part! Buchanan's talents are put to work making beautiful
the center rotating cage controlling the sidereal hour chapter ring.
The first design was an attempt to make the cage pattern look similar to
that used to support the anti-friction wheels in the pendulum assemblies.
The geometry between them was too different to make this visually
acceptable. The next three designs became progressively more elaborate, and
guess what? We chose the most elaborate. Is this a surprise?
The final design is
shown within the context of the wheel that will support it as its center; the
same wheel as was shown in Buchanan's hand six photos prior. Next that
design is transferred onto the cage blank and later will be scribed onto the
surface of the metal.
The first photo shows one of the cage plates being milled to shape.
The next two photos show the rear and front cage plates being decoratively
cut out on the jeweler’s fret saw.
curvilinear shapes now have to be hand filed to final profile after being
cut out from the brass blank on the fret saw. Buchanan makes extensive use
of a fleet of files, first photo. An array of filing buttons is needed to
help shape each curve. In the second photo a steel cylinder is affixed to
each side of a desired, rounded area on the rear roller cage frame, and front
frame in the third photo. Buchanan will file around this cylinder to achieve
a near perfectly round profile for each area that requires this particular
shape. In this case it is the three pivot points for the cage rollers. I
stress that the contours are near perfect with the slight imperfections that
are always present with hand work. These variances are highly desirable as
they lend to the movement being recognizable as being made by a master
craftsman and not a computer-aided machine. To my eye one cannot ever be
confused with the other.
Next the completed
decorative front cage frame and its setting within the center of the wheel
for the hour chapter ring. It is this type of work that sets Buchanan apart from the rest.
There are 68 parts that
compose the sidereal roller cage and twin rotating, concentric chapter ring
platters. There are additional wheels that derive the sidereal minute from
the original sidereal hour.
The following six
photos show the build out of the roller cage driving the sidereal hours and
center hub for the sidereal minutes.
First the cage drive gear has the rear decorative cage plate assembly
mounted to it. Then the part is flipped over and the three cage rollers are
installed. Next the center hub is inserted.
Next the upper
decorative cage plate is installed and next a three quarter view. Finally
the part is again flipped over to the rear view and the center hub’s drive
wheel is attached.
The following photos show associated gearing and
platters which attach to the roller cage and center hub assembly.
The large wheel shown
here is driven by the decorative front roller cage mounted to its center.
Notice that this wheel has a smooth rim. Upon this wheel is mounted the
sidereal hour chapter ring support platter.Next the rear decorative roller cage is attached to the
slightly smaller, 256 toothed, wheel.
Next the same
perspective from the rear is kept and the roller cage assembly is installed.
The sidereal hour and minute drive wheels are seen in the center foreground.
The part in
the prior photo is seen just below the smooth, larger wheel described above.
Next a larger wheel which had existed before in connection with the mean
solar time is added along with its drive wheel. Next the assembly is flipped
over to the front view. The inner minute platter is attached to the center hub.
The hour chapter ring
platter is attached to the outer smooth wheel in the prior photo. Next the
entire assembly is flipped over to reveal the attachment points of the two
Next a close up of
roller cage and center hub.
The cage assembly is now installed within the machine.
Next is the 240 toothed wheel and it is used
to derive the sidereal minutes from the sidereal hour. This is the opposite
of conventional motion work where the hours are derived from the minute
gearing. Conventional engineering would expect this where the faster rotating gear
with more torque (minutes) would drive the slower wheel. However the
sidereal hour was already constructed, and fortunately there was plenty of
power available to allow for this reversal.
The first photo shows
the careful planting of the derivative minute wheel. Next the wheel installed, rear
The sidereal hour and minute counterclockwise
rotating platters are shown. Next dressed up
with dials. Only the mean solar dial is real enamel. The sidereal chapter
rings are mocked up in paper and still have to be made in fired enamel. All
of the dial bezels are also wooden mockups, yet to be fabricated in a
decorative metal design.
The first video shows the rotating roller cage and inner hub of the sidereal
time drive. The outer rotating roller cage portion is the hours and is
connected to the outer ring. The the inner hub is for the minutes and is
connected to the inner ring. On each ring will be an enamel dial to read out
the time. The entire system is driven via the worm gear seen on at the 2
o'clock position of the roller cage. The step up from hours to minutes is
achieved by the large wheel set seen turning on the left.
In the second video one can see the movement of the sidereal chapter
anti-clockwise, or in a retrograde motion. The dial hands do not move during
demo mode as these are tied to the time train. Please note that the
narration should say at the beginning that
Chicago, not Sydney is at twelve midnight.
This is later corrected in the narration.
I remember at the outset of this project that I commented to Buchanan
how I was often disappointed with the side view of skeleton clocks. One
usually saw just two plates edge-on with a few skinny looking arbors between
them, a rather uninteresting sight. I think we have managed to avoid that
This is where we stand at this time. The left side of the clock’s
mechanicals is complete. The right hand side has its main and lower subsidiary
dial complications complete. We still need to create the functions for the small
separate dial, a thermometer, as well as the upper subsidiary dial above the
tellurian, the sun and moon rise and set functions. And finally the central
area is to be crowned with an orrery. Afterward is the fabrication of the
stand and movement crowned with an orrery.