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Debugging continues, sub-base surround built, dedication plate, winding key reviewed -  June 2021

June marks the completion of the machine and the journey now to be trod through testing and ultimately the travel of thousands of miles to its final destination and reconstruction. As this process unfolds, there will be a few additional bugs and tweaks made as needed. This month an intermittent problem with the feed pawl to the celestial train's Robin remontoire is addressed. Bias springs on the strike flies needed to be adjusted as they were a bit too strong. The keyways begin to begin to be located for the front glass.

The sub-base wood surround is built. Other small adjustments are made. The dedication plate and winding key design is discussed. Next month the trialing of the machine for rate and accuracy begins.

 

The raw base material is shown above, the surface is veneered flame mahogany.

 

The completed sub-base surround is finished, except for a brass trim piece that will follow the perimeter of the bottom. The surround will enclose a 2.5", (6.5cm) thick aluminum base block that the clock will rest upon. The aluminum base is needed to ensure that the clock's brass base will not suffer damage from any uneven surface that the clock might otherwise rest upon. The brass clock base is made from four major components which could shift under stress. Attached to the clock's base are several tall frame components that would magnify any errors in the base frame and could result in the binding of the entire main wheel works.

Before the machine was converted from weight to spring drive in October of 2019, a structural steel stand served the function of the aluminum block. After the conversion the stand was no longer needed for the weights to be suspended.

Shown above is my first initial idea for the dedication plate. I did not have the capability of making a bare oval so there is a white square that will eventually be oval. There is nowhere on the front side that a plate could go, so the rear was the only place left with the space needed. Looking at the front, a dedication plate even if it could go there, would be a blemish. Another option would have been to replace the Latin inscription created in May 2018 to be around the planisphere mask with the dedication, but that, in my opinion was not an option since the phrase so nicely encapsulates what this machine represents and compliments the stars represented on the planisphere dial.

This is just the initial design and information.

Buchanan had made something similar in the past for another client, shown above. I like the 3D depth, especially the raised lettering in the oval center that contrasts with the engraving within the perimeter.

Buchanan asked about the type of winding key to be made. I suggested a curvilinear design similar to one shown from my collection, but with a couple of ivy spurs like those found elsewhere in the frame design, and if there was enough of the mammoth ivory left over from the creation of the tellurian Earth globe back in September 2016, that this be used for the handle. I've always liked the heavy, yet silky, warm feel that ivory has in the hand. Over time a beautiful patina develops from handling. I also suggested that Buchanan may want to have some sort of engraving that will connect the key to the clock.

Correcting a bug with the Robin remontoire feed pawl.

 

Buchanan writes: I have a bug with the feed rod from the rear time remontoire to the Robyn remontoire. I want to make it lighter as it is affecting the poising of the Wagner carriage. It should be a simple fix. There is also 1 link in the Robyn chain that very occasionally catches on one of the sprockets. I have had a video camera on the clock most nights and one can pick up a single delay as the relationships between each of the Wagner carriages and the positions of the pulleys on the Robyn must remain consistent. It is very easy to go through a whole night’s video in about half an hour and find one small change. I can then replay it frame by frame to see exactly what happens.

Having the machine under video surveillance is a good idea. It is a complex mechanism and having many dials that record time or position lends well to detection of any malfunction. Buchanan added a counterweight to lighten where the pawl drives the Robin remontoire pulley (left photo above). The original mass of 4.4 grams is eventually reduced to one.

Buchanan writes: With the very light feed roller force, when the Robin remontoir is released and runs down, the two curved latching arms have to be stopped by the unequally spaced release cam (black arrow). This is driven by the roller feed pawl with the new light counter balanced rod. It seems as though when the curved latching arm hits the cam, it knocks the feed wheel on an extra step (yellow arrow). I had this problem may years ago and I don’t quite recall whether it was because I had counterbalanced the feed rod, like we have done now. Whatever the reason, there is a very simple fix. All I have to do is to reduce the diameter of the unequal release cam. This is about 5/16 inch diameter. I can easily reduce its diameter to about half of that and, as this is an intermittent problem a 100 percent improvement in the leverage ratio will fix it completely.

The diagram above shows the feed pawl acting upon the Robin remontoire pulley. What Buchanan refers to as the unequal spaced release cam is what allows the Robin remontoire fly fan governor to cycle at five uneven intervals. What this means is that, in contrast to the main time train fly governors which cycle every thirty seconds, this cycles at five differently timed intervals with a mean time of once per minute. Since this is simply a timing of the release of the remontoire to allow the celestial main train to rewind the remontoire, as long as the rewinding is occurring within the one minute cycle on average, there is no adverse effect on the accuracy of the mechanism. The concept of unequal spacing of the time intervals was chosen to make the Robin fly governor action somewhat unpredictable and therefore more interesting and attention getting. An even and predictable pattern soon becomes ignored by the the human mind, this will add an additional feature, particularly since it is purposefully set deep within the machine, so one will at first notice something shiny glittering behind the complexity demanding from the observer a closer look.

So essentially this bug results in the feed pawl dropping occasionally two steps rather than a single step. This will cause the take up pulley to run too fast in relation to the feed pulley causing a lockup of the remontoire from the slack in the chain being taken up. We have designed for this eventuality because both the time and celestial train share power from a pair of springs (formerly weights) that drive each train. The reason for this design has been explained, but briefly the time train requires about ten times the power of the celestial train. We did not want one weight to be so outsized from the next weight over, thus the sharing arrangement. When the conversion was made from weight to spring, the same constraints were present. A spring large enough to drive the time train on its own would not have fit into the extant space occupied by the original barrel used for the weight line.

Since these two trains share their springs I wanted to avoid the clock stopping if the celestial train should fail. A complex clutch system overrides the Robin remontoire in the event of a lockup, allowing the time train to continue drawing power from the springs.

The new unequal cam, left, will have a smaller diameter than the old one, right. This is illustrated in the drawing above by the black arrow. Instead of a hollow cage with unequal openings, the same design will be cut into the center post allowing for the diameter to be cut in half; lowering the force the remontoire locking detent exerts on the cam.

Another small change is made as follows, Buchanan writes:

I am still working on the Tellurian dial. I have brought the Tellurian forward by 2 mm as it was rather close to the enamel dial. This is just a long term insurance policy. The back of the tellurian mounting post was a bearing for the strike trip so I had to extend that bearing holder. This is not all in place. I am going to have to machine a little of a section of the Sun/mod dial bottom, the concave section. Fortunately I can easily unscrew it without dismantling the Sun/moon dial.

I am constantly amazed how easily most components can be reached in this clock. It is very seldom more difficult than removing a wheel on a chiming clock and mostly very much easier. By removing one, or sometimes both chatons, many wheels between the frames can be taken out. Almost anything mounted on a dumb arbour is easily removed and often screws that appear inaccessible can be reached from the other side of the clock with a long screw driver.

This is the result of Buchanan's careful attention to design. One of these being the extensive use of chatons within pillar frames rather than conventional jewel pivots or ball bearings friction-fitted permanently into a conventional plate. A chaton is a removable pivot, so when one or both are removed the wheel arbor is completely free of the position it held between the frames without the need to part those frames. This is but one example of the many features designed into the machine to make such a complex mechanism as easily serviceable as is possible given the intricacies involved.

The clock is connected for the first time to a Microset® timer to begin test and rating. This will begin in earnest next month.

 

The Astro-skeleton is now ready for shakedown trialing.

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