Orrery, completion & a major design change
from weight to spring-driven power -
This month the orrery which will crown the clock is completed with
the exception of the final dial, still being finished up in China, and dial
bezel ring. We also made a major design change perhaps second only in
significance to the frame redesign in March 2009. The way
the machine will be powered is being changed from weight to spring drive.
The many advantages are described in this installment.
In these two photos
Buchanan begins to grind and polish the new, larger opal stone for Saturn.
I was working, mounting the planets today and found that I could enlarge
Saturn substantially. I have also started making its ring. A stone ring
would be far too fragile. I also don’t like supporting the ring by only two
pins as I have done before, as the ring can swivel around the two pins. Not
a problem with a simple orrery, but, this one has the tilt defined, so, I
will make a three legged spider to support the ring. I decided to make the
ring and spider out of sterling silver. I found a piece of opal with a
better colour for Saturn. Like blued steel, the lighting make a big
difference. It looks better than these photos show. So Saturn will be about
the same size as Jupiter. A more realistic size in comparison to the other
planets.I agree the new opal is far better, I really
like the bluish color patch.
have been working on Saturn. I have made the silver spider and ring.
The first photo is the piece of silver before I started to rough machine the
spider. You may notice that it is the off cut from the bottom of Mr
Perroult’s silver dial. The next two photos show filing the arm to a rivet
to fit into the ring. The fourth is the ring being riveted.
Notice by this time the spider has
been curved to fit the three attachment points on the ring. The Perroult
clock was the clock Buchannan had made before this project.
Saturn’s ring looks a lot like the steering wheel from an antique car.
This entire assembly is less than ½” (1.3 cm), yet Buchanan still adds
incredible detail exemplified by the bevel to the Saturn’s ring as well as
the decorative turning on the base of the ring’s mount to the arbor.
Saturn and its ring assembly now mounted within the Saturn planetary
The Sun as represented by a rutilated quartz sphere is now mounted in the
center of the orrery. Notice the optical effect it has in lensing the
balances behind it. Once again Buchanan makes a finely turned mount for it
to rest upon.
These four photos show the gold leaf applied to the lapis sphere
representing the earth. After the stone sphere was completely covered
Buchanan then cutout the oceans surrounding the continents represented by
the gold leaf.
I fitted an end stone under the Earth arbour pivot on the orrery and we have
a substantial improvement in the even turning of the earth, I am now fixing
a dumb arbour on the Saturn gearbox and then I am satisfied with the orrery
for now. I had noticed the jerky
motion of the earth in a prior video, and had not even mentioned it to
Buchanan. Again he is on it right away.
The natural stones and pearls are shown here depicting their place within
the orrery and tellurian. Only the Mammoth ivory Earth sphere is missing
from the tellurian as this was difficult to remove for this photo.
The orrery is now complete.
The crown upon the machine. Can it get any better?
This video demonstrates how the clock looks to the
viewer at different eye-levels. Once the orrery had been placed within the
mechanism, we realized that to get a better view of this complication we
would need to lower the height of the clock by about four inches.
Buchanan now begins the final finishing work for the Fasoldt fly fan
Buchanan uses a spark-eroding band saw equipped with a 20 thousands of an
inch blade to cut the curvilinear fan blades. This fine cut and detail would
have been very difficult to have achieved using conventional mechanical
blade cutting due to the very thin brass stock. This method achieves a very
smooth cut with an intricate outline.
spark-eroding band saw using a 20 thou wire to cleanly cut thin brass sheet
for the fly fan blades on the strike trains. Notice how fast the wire
un-spools from the supply drum.
Here we see the difference between an intermediate finished part and the
final finish. This involves more than just a smoother, brighter surface
finish but also a change in the dimensions of the part to finer, more
delicate and elegant proportions.
The two pair of fly frames are complete. The second photo shows the final
conversion of the plain pillars to their final decorative form.
The fly fans, pillars and frames are hung out to dry after lacquering.
The completed strike fly assemblies. Notice the display of multicolors with
just this one part, silver, blue red and gold.
This photo clearly shows the decorative pillars.
In this photo one sees the cherry-red color of the jewel pivots.
This video shows the finished quarter strike fly fan
based upon Charles Fasoldt's design using epicyclical gearing. We have made
a modification to that design by using an internally toothed wheel to make
the detent whip move in the opposite direction as the fan assembly. This
lessens the impact of the whip upon the pallet jewel used to lock the fly at
the end of the quarter strike sequence.
Pendulum balance poising weights
Buchanan needed to make some poising weights after certain changes were made
in the way the cross bands were retained, That design change made it easier
for the user to remove and attach the wires.
This video montage shows various sections of the Astro-skeleton clock
as of July 2019. There are still a few things that need to be fabricated; a
host of bugs and adjustments to be made. Then the machine must be completely
disassembled, polished, frames lacquered, various screws blued, all of the
roller bearings in the main trains replaced with ceramic bearings to make
the machine largely a dry-runner. Then case work. As one can see, for pure
showmanship, this creation is tough to beat. We believe for its size, it is
the most complex skeleton clock ever created.
A major design change is initiated to improve
the functionality and practicality of the machine
Rex Swensen has avidly followed this project for some time. He has been
involved with the creation of a series of clocks based on James Condliff's
elegant curvilinear frame design from England c.1860.
is really too late for me to make this suggestion, but did you ever
contemplate the use of Constant Torque Springs in your Astronomical Skeleton
clock instead of weight driven. They have 27 active turns and do not require
a fusee. Design life is 5,000 cycles, so for eight day running that gives a
life of 100 years. In the overall design, I personally think they would fit
in better and be more appropriate than the weights.
We are using them in our replicas of the 1860 Condliff two barrel clock
instead of the normal spring barrel and fusee. They come in a very wide
range of torque specifications. The second photo is the same clock made by a
colleague in the Sydney Clockmakers Society. He is about a year ahead of me,
but then he had a set of water jet cut plates – but lots of edge filing
first photo shows the springs in the Rex Swenson Condliff replica. Here the
regular spring barrel and fuse are replaced with
one pair of constant torque springs used in the Condliff replica to power
the strike train. Another pair is used on the opposite side to power the
time train. Unlike a regular spring contained with a barrel, this spring is
wound around a pair of spools. The length of the spring when fully wound is
mostly on the upper spool and travels downward to fill the lower spool as it
The next illustration from a catalog describing a typical spring, here
referred to as a motor spring since it has the constant force of a motor to
drive the mechanism it is intended to.
This idea came at just the time we had finished the orrery and realized that
to get a good view of that assembly we would have to lower the entire clock
by about four to six inches to get the best perspective. This reduces the
weight drop and we would lose our intended eight day duration. The springs
would eliminate those weights allowing us to have the clock at any height we
I had my doubts about whether such springs would be powerful enough to drive
the time train which required about 120 lbs (54 kg). But Rex and Buchanan
were positive they would. At first I was reluctant to do away with so much
beautiful brass represented by the weight shells. However, this idea of a
spring-driven mechanism was contemplated by me before.
This drawing is dated July 24, 2005 and was one of several I had made
contemplating different dial designs and other technical details of the
clock. In this rendering I use conventional springs
as well as fusees.
(I was unaware of motor springs at the time). This was discarded since
conventional springs would prove to be too large and if possible would
contain an enormous amount of power that would represent a real danger of
damage to the mechanism should they fail. I asked this same question about
the event of a spring explosion with motor springs and apparently they do
not pose this hazard. Had motor springs been considered it is quite likely
this would have been the original design.
It is interesting how many details of the design from this very early
conception were retained in the final machine.
Here is a view of the clock with its compliment of weights. The stand has to
be made of structural steel to support the clock's frame since it is not
strong enough to support the weight set without distortion to the frame. The
entire set is approximately 220 lbs (100 kg). The stand adds another 120 or
so lbs (54 kg). By using motor springs we eliminate about 340 lbs (155 kg).
The entire clock with glass case is estimated to be 220 lbs (100 kg), so the
entire setup would originally have been 560 lbs (254 kg). This change reduces
that weight by 60% and makes the entire machine far more manageable to move.
One can now place it on any suitable, yet sturdy table top. I think many
people who have followed the project may be surprised to see this
photo. Nearly all pictures taken of the clock have been from the level of
the table top.
This is one of a very few videos taken of the clock with its compliment of
weights. It was taken back in August 2016 before completion of the sun/moon
and orrery complications. The planisphere is still a mockup here.
On the aesthetics aspect, personally I think that massive weights look out
of place on a skeleton clock like yours. OK for wall clocks and long case
clocks, where the case design is in harmony with the weight drive, but not
for a skeleton clock potentially intended to live on a side board or
I'd tend to agree with his comments.
Buchanan saw the advantages of the motor springs early on, before I was
I write Buchanan in reference to the spring design: Just
curious, do these things even have the torque to do the job? Or the length
to last eight days?
Later in the day Buchanan writes:
We need 1.8 kg at 10.5cm torque to wind the time train. This is 19kg cm or a
single SR94 in the catalogue. Width 2 inches, largest diameter 3.34 inches,
smaller than the largest diameter of our drum. We only need 24 turns of the
I need to check how we could fit them in to keep winding the same, with
maintaining power (indicators). They are also stainless steel. I think we could do a
clever, and cross two over between two winding arbours. Very little
modification to the clock.
Other advantages. : Much, much lighter. Far more portable. Much less strain
on the clock frames and main arbour bearings. Completely sealed case. No
lead to ship or cast. No danger of cables breaking. No Harrison balance type
clock had weights. They are not unattractive either.
The idea of a completely sealed case was also vey appealing. With weight
cables one cannot have a sealed case.
The decision was made in about a week's time. I have to thank Rex for his