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Orrery, completion & a major design change from weight to spring-driven power - July 2019

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.


Buchanan writes: 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.


Buchanan writes: I 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 ” (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 assembly.


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.  

Buchanan writes: 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 assemblies


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.


CAM 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.

He writes:  It 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 needed.

The 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 unwinds. 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 wished.

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.

Rex writes: 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 similar.

I'd tend to agree with his comments. Buchanan saw the advantages of the motor springs early on, before I was convinced.

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 27 turns.

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 contribution. 

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