The real downside of this is the breaking of symmetry between the time dial
and the tellurian dial. The combined time and sidereal dial is thicker than
the tellurian dial. There
may be some action we can take with the bezel work on the tellurian dial to
alleviate this issue.
To be fair, perfect symmetry has already been broken with the setting dial
for the equation of time kidney cam located below the time dial.
The diagram shows the
difference between the sidereal and mean solar day. Briefly, sidereal
time is a time scale that is based on the Earth's rate of rotation measured
relative to the fixed star rather than the Sun. A mean
sidereal day is 23 hours, 56
minutes, 4.0916 seconds (23.9344699 hours or just under four minutes every
twenty four hours shorter than a solar day.
Drawn here is the sidereal,
equation of time and calendar drive components. These originate from the center
arbor under the escapement support structure, number 4, and flow four wheels
to the left to split with two bevel wheels that each drive a worm gear, (two
yellow arrows) the lower for the equation
kidney to rotate once per year, and
the other a worm to turn the sidereal time
dial counterclockwise twice in one year.
We could have used bevel wheels in place of the worms configured like those
employed to drive the remontoire fly fans, but I wanted to introduce a worm and
helical gear, components that have not yet been used in this project.
The mating drive bevels will need to be
of differing diameters and not the same as shown in this diagram. The second and third
wheel from the center drive arbor will also contain winding squares that will be
used in the celestial demonstration feature. Wheel number 2 has
a winding square that will demonstrate the celestial functions at a rate on one
turn for each 24 hour period. Wheel number 3 has a winding
square and multiplies the turns per day by four. Number 1 has a
winding square and
demonstrates the interplay between solar and equation time. The
red arrow points to a wheel with
four pins which turns once in twenty four hours. These will drive the perpetual
First Buchanan makes the wheel train in plastic
in order to check for fit within the existing movement. This also allows him to
position these wheels in the most aesthetically pleasing way and to plan the
frame work to support those wheels. This as well as the initial drawing of the
wheel train against a photo-grey copy of the exiting movement is a standard
Now the wheels begin to be fabricated in metal. As has been done many
times before, the rough wheel blanks are cut from brass stock, the center
arbor holes are drilled and then the perimeter wheel teeth are cut. The fourth photo
shows a pinion being cut with a fly cutter.
wheels in metal are fitted to the movement to check for functionality and fit before
they go on to further finishing. These wheels represent the main drive
before additional wheels are attached that branch out to the equation,
sidereal and calendar functions. Next the outer plate blank is put into
position. One can just see the inner plate behind the wheels in the first
Here the additional wheels that branch off the three complications are
made. Compare the fourth photo to the finished product later in this
The outer plate
shown earlier is now in place with a few of the additional wheels mounted
outside. Notice the two winding squares with a key attached to the left most
square. These are part of the three speed celestial train demonstration
drive. Next another plate to go in front of those wheels shown in the prior
photo as well as additional wheels that will continue toward the left.
The plate is now in position with holes
drilled for positioning. Next sections are removed.
More parts are rough cut out of the plate as
well as the new mating plate. We now have a separate “plate and spacer” subframe for the equation and sidereal drive wheels to be mounted within.
Next the arbors are finished to the familiar
shape with tapered ends.
Each of these are composed of a stainless
steel arbor with hardened steel pivots fitted into each end. Next the rough
frame is fitted out with jewels and then the arbors are inserted to check
The first photo shows the equation and sidereal drive wheels fitted
to one of the plates. In just this one small sub-frame one sees as many
wheels as in a simple conventional clock. Next the assembly is shown fitted
to the rest of the machine.
Here is explained the
three winding squares shown in the first photo. Number 1
demonstrates the interplay between solar and
The two numbered 2 and
3 are the two speeds that one will have in demonstrating the entire
celestial train along with the calendar giving a temporal reference to the
entire demonstration. Number 2 will allow one to crank the square to
represent one turn for each day. Number 3 is a divider equal to four
revolutions for each day. Number 4, the next one over and directly below
the escapement is the control for the two speed drive for the orrery. It also connects
(locks) the celestial functions to the clock to operate them in real time
and allows for disconnection of these for the demonstration mode. At the
slow speed one will be able to run all celestial functions including the
orrery by the first two cranks. The second faster speed is a 12:1 ratio and
allows one to demonstrate the orrery disconnected from the rest of the clock
since the outer planets have long orbital times with Saturn at over 17 years
and this cannot be displayed with the calendar function providing a temporal
To the far left is an
additional square, number one, which has a key inserted. This demonstrates
the equation of time and mean solar time showing the hands moving together
and showing how the equation hand will precede and regress behind the minute
hand by approximately fifteen minutes throughout the year. This is a
stand-alone demonstration and is separate from the calendar function and the
celestial train demonstration functions. This was necessary as even with the
slow speed celestial demonstration speed at four turns per day, it would run
much too fast for the solar/sidereal minute and hour hands. It is the same
reasoning but for opposite conditions that the orrery has a separate high
speed demonstration function separate from the celestial demonstration.
The last photo shows
the main time dial ring and the smaller dial representing the former design
and location for a separate sidereal dial. In a fortuitous turn of events it
turns out that this dial can be repurposed without any modification into a
world time dial. We talked about having a dial located in front of the
second wheel to the right of the equation wheel train. That wheel will turn
once in twenty for hours. One idea is to have a ‘world time’ dial where
various cities local time can be represented with a hand designated for
each. Since the dial is rather small at about two inches, we could only fit
five or so cities, say New York, London, Paris Moscow and Beijing. A pretty
good idea as it adds another legitimate complication. We would need to
balance this with another dial opposite to keep the overall symmetry of the
dial layout across the movement. One solution could be to have another would
time dial located at that spot, perhaps for the southern hemisphere. The
fact that this dial is also delineated with two colors for each twelve hours
on the twenty four hour dial gives both day and night indications for each
Now on to the screws needed for this part of the project, many which will be
used to attach the wheels to their collets as well as other parts of the
drive components. The first photo shows the raw rod stock for the screws
made in the second. The next shows a close up of a saw blade used slit the screw
heads Shown in the buckets are 160 screws 1.6 mm and 0.9 mm diameter.
Next the wheel collets
are fabricated. After the blank is cut, the holes are drilled and tapped.
The next two photos show the decorative machine work
The finished compound
wheel set. Note the beautiful concave feature on the collet rim. Compare
this to the wheel blanks that composed this piece in the sixteenth photo
earlier on in this installment.
The first two photos
show the front and rear of the two wheels with their winding squares
responsible for the two speed demonstration of all of the celestial
functions. Next the first of the remaining wheels in the drive train.
The wheel characteristics become more delicate as one goes out from the main
Here we have the
complete drive with all wheels planted on the rear plate, so what one sees
is the wheel set from the rear. Note that if this were flipped around the
large curved cut in the plate would match that of the main dial pictured in
the diagram to the upper-left corner.
The first photo shows
the existing post mounted to the time train frame post. Upon this are
mounted the equation drive, kidney cam and setting dial. These parts are
mounted onto a threaded cannon pinion shown in the second and third photo.
The assembled parts are in the fourth. The knurled nut is the kidney cam
clutch used to allow the kidney to be adjusted and then screwed down to lock
it in place. In the last photo the rear disk blank is the
kidney drive wheel and the kidney cam will be fabricated from the front
Here begins the
sidereal time dial ring. First the hub upon which the dial and its drive
will rotate is fabricated, yellow arrows. This is fitted around the existing
triple set of cannon pinions and central arbor carrying the seconds hand. It
is fortuitous that these were designed with enough length to accommodate the
new sidereal hub since those were made long before we introduced the design
change necessitating the new hub. Next photo shows the hub with the dial and
drive disk blanks. Next is a photo of these parts mounted to the machine.
Lastly the sidereal dial blank is shown with its circumference mirroring the
adjacent plate cutout.