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Continue tellurion assembly - January 2016

This month the tellurion has the sidereal and synodic lunar complications and the Moon and Sun horizon complications added.


Here Buchanan is engraving the ecliptic ring. The ring comes in two sections, second photo.  He had to make a special left and right hand jig to hold the main ring with a very thin clamp washer and then machined away the washer where he had to engrave. Then he had to repeat the whole procedure for the other side, as the ring does not have symmetrical engraving. All of the rings that girdle the Earth globe are engraved on both sides.


The first diagram is the design for both the sidereal and synodic lunar month dials. Next are the completed dials. I wanted to present the completed dials before showing how they were made so one could see how faithfully the real thing was reproduced from the artwork design. The outer chapter ring is just 1.25" or 3.1 cm in diameter. This is on the scale of a wristwatch dial. An explanation of these two functions was given in the November 2015 installment.

The copper disc in the first photo has diamond powder pressed into it, so it is a diamond lap, mounted on an old disc drive bearing. Buchanan can tilt it to any angle. He spins it with a small electric motor and slowly moves the mill table toward the engraving cuter until it grinds an angled flat on the side of the round carbide rod held in the machine spindle. It is then backed away and the spindle is turned 90 degrees. This process is repeated 4 times to produce a sharp inverted pyramid point on the cutter that is perfectly true to the bearings of the spindle. He can engrave a much finer line with this, as the point of the cutter runs perfectly true, and does not cut an oversize circle. Buchanan’s method of sharpening a tool to a finer caliber than commercially available has been used on the fret saw blades used to cut all of the flat stock in the clock. This allows for very fine, accurate and smooth cuts on his many filigree shaped parts.


Both dials shown to scale. First the outer chapter ring and second the inner disc.


Buchanan now gets ready to mount a tiny indicator hand underneath the outer sidereal dial. This hand will be used against the synodic dial and can be seen in the circled area. Even at this small scale the pillars holding the dial are decoratively turned.

Now the sidereal indicator is shaped by hand filing, circled area. Next the blued hand is ready for mounting onto latitude ring. Notice that the hand is not a simply flat configuration, but has a special profile to allow the pointer to wrap around and be exactly in line with the ring's edge profile. This avoids the “stuck on” look that many other less careful makers might resort to.

The dials are now installed with both the inner indicator hand attached to the sidereal dial to read; off the synodic dial, lower circled area, and the hand attached to the latitude ring which reads off the sidereal dial, upper circled area.


One can now get a feel for the intricate and voluminous amount of engraving in connection with the Earth globe within the tellurion assembly. All of the engraved areas will later be silvered. The Earth at this point is simply a crude mockup.

The Moon eclipse pointer is now being made from the rough stock. In the next photo the tiny screws are being threaded and next the finished screw set. The two shorter ones will secure the pointer. They are less than 2mm in length. These are another example of the small pocket watch scales we descend to in the various components of this project.


The Moon eclipse pointer is now completed ‘in the grey’. Next it is given a quick bluing and mounted to the underside of the frame supporting the moon carriage, arrow. For some time now Buchanan has been semi-finishing the parts as he goes along so as to give me a better understanding of how the overall machine will look before the final task of finishing.


Based on Mathias Hahn’s original design there were a pair of curved arms that move with the orbit of the Moon to reveal the rise and setting of the Moon on the Earth’s surface, see July 2015 installment where Buchanan first began fabrication of the tellurian.


The Moon horizon arms are now attached to the sidereal chapter ring. Notice the small turned pillars securing the chapter ring to the underlying frame.


The sidereal and synodic moon chapter rings are now silvered and the Moon horizon arms are in place. Again it should be said this is only a demonstration stage. These will later be highly finished and then re-silvered and black wax applied to the engraved areas. The next photo shows the Earth with the Moon horizon arms.


In the first video we see the pair of curved Moon horizon arms rotating with the orbit of the Moon in fast forward and giving the observer the position on the Earth where one could see the Moon. This, of course also depends upon where the Moon is in relation to the Earth and the Sun as to whether one sees the full, partial or no Moon at all. One can also see how the sidereal and synodic lunar month chapter rings are read just below the Earth globe.

The second video explains the way the tellurion is able to predict not only when, whether in the future or past, but where on the Earth a solar or lunar eclipse will occur. It must, of course be remembered that with a mechanism so small as this one where the Earth globe is barely under 1.5" or 3.5 cm in diameter as well as the small season sector dials, the accuracy is limited.

Hahn's design only had a provision for the Moon's horizons.  After I saw the video demo of the Moon horizon arms I wondered if we could not also add another set to indicate the Sun’s horizon. This would give another legitimate complication and the interaction of the two arm pairs passing between each other would add another interesting feature. At this scale there are many problems with clearances and we discussed the details of the implementation. This is one of several examples of changes and additions I had asked for as this project progressed over the years. Buchanan has always gone the extra mile with me on these.


Here Buchanan makes his preliminary attempt to fit the additional Sun horizon arms into the existing system. It is obvious that the Sun’s arms are way too thin in relation to the Moon’s. A rebalancing between the two will be needed.


The Sun horizon arms are complete. Unfortunately they must be attached to the top of the synodic chapter ring; partially obscuring the engraving for the words ‘Lunar’ and ‘Month’. It was impossible to attach the arms from below because even though the synodic ring is positioned slightly below the sidereal ring, there is virtually no gap between the two and so no room to thread the arms between them. But this is in my view an acceptable compromise to get another interesting complication.

Notice the large piece of brass plate toward the rear of the tellurion in the second photo. This is the beginnings of the counterweight that is needed to poise the entire rotating assembly. Nearly all tellurions and orrerys for that matter are mounted with their mechanisms in the horizontal plane. This obviates any need for poising, but our mechanism is mounted in the vertical plane and thus must be able to rotate without any imbalances.

In this video we see how the Moon and Sun horizon arms operate at an accelerated pace. The Moon horizon arms follow the orbit of the Moon remaining stationary with respect to the Moon while the Sun arms remain stationary with respect to the Sun. There was a glitch at the very end of the video, since corrected!


Buchanan now begins the fabrication of the tellurion counterweight. Notice the portion of the top frame that caries through to the central boss. It is in the same sickle shape as those used to hold the remontoire drive weights in the time train as well as the counterweight in the strike and repeat pumper assembly. Attached and underneath the sickle frame is the wider semicircular poising weight. next the lower tellurion frame is attached.

These photos show the central drive wheel to the tellurion. The first photo shows the clutch assembly consisting of a shaped ring within a casing. That casing then screws down via a knurl to tighten down the clutch. This is one of many safety devices installed within the machine to prevent accidental damage from operator error. In this application the entire tellurion can be moved against the drive wheel without damage.  


The proposed wheel configuration for the tellurion drive is depicted in these two photos. In the first one there are an additional three wheels rising above the tellurian axis and these have to do with the sun and moon rise complication that will be located above the tellurian (yet to be built). Notice the very large wheel near the center. This is nearly identical in size to a similar wheel that is behind the main time dial and could be seen within the original mean time chapter ring before we made a design change and added the two additional sidereal time rings. I had admired that large, delicate wheel and asked Buchanan to find a way at some point in the project to create another one. I’m happy to see it prominently displayed here. It is about 4” or 10 cm in diameter.

The drive wheels to the tellurian are now being fabricated. These photos show two of the four wheels that will be needed.


Now Buchanan makes that large wheel I was looking for within the drive train to the tellurion. Isn't this simply the picture of delicacy? If his hand were to twitch would not the wheel crumple like a delicate flower? And since we have such a nice, large diameter wheel, why not double the number of screws to secure it to the collet?

The four drive wheels are depicted by the yellow arrows. The first wheel, 1 connects to the central pinion off the two speed transmission that also is used to disconnect the entire celestial train from demonstration mode and into regular time train mode. It also allows for a 12:1 speed step up to the central orrery (yet to be built). The arrow all the way to the right, 4 is the tellurion drive wheel equipped with the safety clutch.

This photo shows well the many layers of frames and wheels within both the tellurion and the calendar assemblies. Here the poising weight has yet to be refined


The refined poising weight is now installed

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