Back Up Next

Spring drive conversion, begin work and begin clock disassembly  - October 2020



Test rig to determine the torque characteristics of the motor springs. Next photo shows the sliver cut from spring hub to provide a constant radius at the attachment point.


Video of a sliver being cut from the spring hub with EDM machine to make a constant radius surface where the spring will be attached to the hub ensuring there will be no stress to the spring at the attachment area. The cut sliver will then be used to clamp the spring onto the hub.

Buchanan writes: I am working on the spring barrels today.

I built a quick test rig for the springs and they match the design specification well. So we have about 10% more power than the present weights.  This is looking very good. Third photo.

I have started to machine the spring barrel centre sections to have a lead in for the spring ends.  I have cut a constant radius curve so as not to create any stresses in the spring ends.

This is shown on the last photo where a sliver is cut from the brass cylinder blank and will act as a clamp for the spring attachment. Not even the manufacturer of the spring specs for this but it is best practice. Another example of Buchanan's “Gilding the Lilly” with respect to his work.

I realised that there is another advantages in these springs over against conventional springs: You can visually inspect them every time you wind them. If one was to start cracking I would expect it to happen over a few cycles.  There is a very good chance that one would see, or, hear something out of place if it started to crack. My guess is that if a crack were to develop it would split immediately without the chance to catch it via an observation. In fact I would hope my face would be nowhere near the spring at the moment of that event.

I also have the barrel flanges roughed out. I will be ordering the bearings tomorrow. I will be installing hybrid steel ceramic bearing as I go.

If all goes well, tomorrow I will make sure that I have a good video recorder working and will start the main strip down, as I need dimensions from the clock it’s self for the new spring barrel arbours.

At this point the machine is being taken down to its component parts for the final miscellaneous fabrication, polishing and finishing many larger parts including frames are being lacquered. In this video, Part 1, Buchanan illustrates the process of disassembly prior to shipping. This involves the removal of most of the clock's complications which have been designed as modules for just this purpose.

In this video, Part 2, Buchanan illustrates the process of disassembly prior to shipping and in this video the process of complete disassembly down to the individual components begins which is necessary before the final finishing process can begin. The three main modules, time, celestial and strike are removed from the base, (the strike has two trains in one hence four main drive barrels in the base). Clearly this is not a simple process, however, if this were designed as conventional clocks with all the train wheels between one set of plates , it would be near impossible.

In this video, Part 3, Buchanan illustrates the disassembly of the clock base. This contains the four main drive wheels and the state of wind complication for each. Besides the fact that this disassembly is necessary for the final finishing stage of the clock, the barrels must be re-engineered to power the machine with constant force motor springs in place of the current conventional weights. There are many advantages to this decision, the elimination of about 250 lbs. in weights and another 150 lbs for the substantial stand to hold the machine. That stand was specially designed to support the base frame as it could not handle the weights on its own without deflection. Now the machine can be placed on any substantial table top at any height and still retain a full eight day duration. The entire mass of the project has been cut by over 60%.

Notice the clever engineering that Buchanan used to make the frame look as if it were molded from one piece. No screws or attachment points can be seen throughout the base frame. That method could only work visually if the frame parts were machined to fit perfectly together. This is something few will ever see or comprehend when observed in the future. A puzzle for them!


Buchanan writes:

I also ran all the clock over the scale in pieces. It is as follows: main frame, carrying frame, time train and strike train weigh 154 lbs.  The celestial train is 19.8 lbs, so the bare clock as you will have to carry it including the carrying frame weighs 180lbs max. or 90 lbs per person.  It feels heavy but not dangerously so, as the carry frame is ergonomic.

Other components are; Bronze balance spheres 26lbs, bells 2.2lbs, Planisphere 4.2lbs, Calendar, 1.1lbs, Sun moon dial 2.2lbs, Tellurian 0.66lbs, Orrery, 1.75 lbs. 2 balance assemblies without balls 4.4 lbs for both, extras(thermometer and transfer gears escape wheels etc.  6.6 lbs.

This gives us a clock weight of about 230 lbs. of which 50 lbs is easily removable.



Buchanan writes: This is the clock in all its major sections. I added up the length of video time and the complete dismantle took 1 hour and 13 minutes of video.  With all the set up and stands to be made as well as downloading etc. it has taken more than a day.

These photos almost makes the machine look less complicated than it is. Everything fits onto a simple table. But obviously if one were to zoom into a close up of the individual components the complexity would come to the fore.


Buchanan writes: Attached are photos of a modification to the Robyn feed pawl. As it has a slight dog leg bend for clearance, it is slightly imbalanced so I made a counterbalance so that it lies in a neutral position on the c shape bearing and roller. I have, in other words lowered its centre of gravity to make it stable.

These two photos show the reworked feed pawl. The poising weight is a beautifully turned tear-drop shape and is attached to another well-shaped attachment to the pawl via a blued rod and is adjustable and secured by a tall-blued screw. The dog leg mentioned is the slight curve where the poising weight rod is attached seen in the second photo.


This photo shows the feed pawl posing weight assembly within the circled area and the weight indicated by the arrow.


This photo shows the opposite end of the pawl resting upon a guide fork (currently temporarily attached to the frame via super glue) and has a clevis at the end, partially hidden behind the frame upright, attaching the pawl to the remontoire assembly.

Buchanan writes: Today I designed the spring barrels.

As usual space is tight, particularly on the time barrels and our stop work, state of wind indicators and maintaining power all complicate things.

Each barrel assembly is completely different to the next, this is because the great wheels alternate in front and behind each other at the same time as we change spring sizes.  I also have to take the drive to the stop work through the idler spring barrel if the drive spring is in the front and the drive to the bevel gears has to go through the idler barrel when the drive spring is at the back. Then through it all there is the main arbour which carries the ratchet wheel at the back of the clock. So we have a triaxial drive at some point on each main arbour. I am also limited by the bearing sizes that are available as stainless steel ceramic hybrids. I feel like a juggler that has just finished a juggling 7 hour marathon. See CAD drawing above.

I am wondering if the weights would have been less work (I am being silly here, not complaining.) It will be very interesting to watch when the clock is wound.


It’s unfortunate that we will not be using 100% ceramic bearings, but they are nearly ten times the cost of the hybrids and more critically are not available in all the sizes we need. Still these bearings are far better in performance and longevity with very little lubrication and the metal cage rings are stainless steel; far superior in all respects to conventional bearings. Buchanan says that even if the oil dries in 20 years, there will be a coating that will perform well given the dissimilar materials of stainless steel cages and ceramic balls, compared to like materials. Furthermore, we are using shielded bearings that have integral dust covers and in many cases those are covered by a faux jeweled chaton for additional protection against contamination. When this project was first conceived sixteen years ago we had not even considered bearings that were not made of conventional metal throughout. Ceramics were confined to NASA and military applications and even the hybrids cost ten times what they are today.


Buchanan writes: I have the spring clamps complete. Today I am making the end caps and bearings for the idler or storage drums.  I have almost everything of the lower frame dismantled. Making those lead in curves for the springs is what Buchanan referred to earlier as a “constant radius curve” for the lead in of the springs.


Buchanan writes: Here is a photo of the new spring barrels with the extended length winding squares, (First photo). There are 28 bearing fits, 8 threads, 8 part fits and 8 squares in total as well as many length critical dimensions. I just have to cut 4 small key ways and they are complete. (It was decided some time ago that all of the winding arbors needed to be lengthened because the two inner arbors were too short; being adjacent and too close to the planisphere frame where the winding crank was inserted. The other two were lengthend to match.) Today I am working on the actual spring drums and spring clamps. I also have to order some more stainless steel for the drum parts.

The spring barrels are progressing well, second photo, I have all 16 flanges complete.


Tomorrow I will start the sleeves that carry and connect everything. Then we should see it all start to come together. When the barrels are assembled I will add turned decoration where applicable. Everything looks very square right now. I have also ordered the first batch of bearings. I have the stainless steel sleeves that carry the storage barrels complete, fourth photo, I have to make two more stainless steel spacers and 150 odd screws and I can start to assemble the barrels. I have ordered the first batch of bearings. They should be here soon. Coming from the USA.


The holes for the storage barrel flanges are now tapped and drilled.


A completed main wheel. Each has two barrels. The barrel’s main spring is the larger diameter with the screws that secure the “constant radius curve” section that secures the end of the spring. The smaller barrel is the take up, or storage barrel from the spring that will be spooled onto that barrel from the adjacent main wheel barrel, it too has a constant radius curve on the opposite side for the spring’s attachment point. Each barrel moves independently since the springs they attach to will spool at different rates over the short term, but over the entire eight day duration should all be unspooled to nearly the same degree. Not unlike how the going barrels or winding drums operate on a quarter strike clock where the time and strike trains all move at different rates and times, but over one week's time the weights are at about the same level when rewinding needs to occur. 

It is interesting to note the similarity in the pair of barrels of different diameters to hold the supply spring and the take-up spool. Look at the old barrels standing on the table below, these too were of a dual diameter design, but used in a completely different way. It is a serendipitous that such a dramatic redesign could be accommodated without having to dispose of the entire main wheel assembly.



The main barrels and take-up spools for the conversion to constant force springs are ready for finishing and reassembly. The four old weight barrels are seen in the background

Back Up Next