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Continue tellurion assembly - August 2015 

This month we continue the fabrication of the tellurion complication.

This is a scale drawing illustrating a side elevation of the complete tellurian structure. The wheel outlines shown above are color coded for their function as explained in a drawing showing the top elevation of the assembly last month, Red = Mercury, Yellow = Venus, Green = Earth, Black = Moon, Blue = main input drive to tellurion. Not all color coded wheels of a particular color are all adjacent to each other, but may be located elsewhere and working through other wheels to their final destination. Look carefully at the extensive use of ball bearings in this assembly, a departure from the traditional use of nested cannon pinions. In this application the  axis is mounted horizontally, (not vertically as represented in this drawing) a departure from the normal presentation. A traditional set of nested cannon pinions would have presented an impossible amount of friction to overcome in this orientation. The use of the term horizontal and vertical can be confusing. If one applies this to the dial of the tellurion then this will be presented in the vertical plane, but the axis of all of the arbors are in the horizontal plane.

Notice how Buchanan has accounted for the clearance necessary for the wheel works to miss the yet to be fabricated dial bezel shown to the left in yellow. The arrow to the right shows the lowest point of the wheel works necessary to clear this obstacle.


The color coding is revealed in this schematic. One can now follow where the wheels information flows to from their source to their output destination.  

The first photo shows raw material that will be turned into the main mounting center for the tellurian assembly. Next is a photo of the two parts that will form the 'quick release' assembly for the attachment point of the tellurion assembly to the clock movement. The conical part, red arrow, is mounted to the clock frame assembly. The part within the lathe collet is the female component that will mate to it. The third photo is the 'keyway' that will be used to lock the assembly to the main frame of the clock. This release feature allows a complete subassembly to be easily removed from the main movement and is duplicated in other areas of the project, most recently in the previous complication, the perpetual calendar assembly. We plan the same ability for the planisphere and grand orrery complications.

The stubby bolt in the photo directly above the first photo pictured here has now been transformed into a slender, multi-tiered spindle the will serve as the central axis for the tellurian, and is seen next to the frame attachment piece. Next the arbor is attached to the quick release mount on the frame of the clock.

Here we see the sleeves for both the input drive to the tellurion and armature drive for the Earth/Moon system. These mount concentrically upon the central spindle.

The first photo shows the initial appearance of the two main frames for the tellurion. Ultimately there will be an additional two sub frames; resulting in a triple frame overall. The gap between these plates is 0.25 inch or 6.35 mm. It looks at this point to be a very small space, but when the frames are fully cut out it will look to be sufficient. In the second photo is a set of precision gauge blocks milled to the nearest thousands of an inch. These in conjunction with rod stock of known diameter is used to set up the correct angle for the moon's node cam as shown in the photos below.

These six photos show the set up necessary to drill an oblique hole in the center of the cam that accounts for the moon's nodes, the rise and fall of the moon above and below the ecliptic (center line) of the Earth. The first three photos show the jig used to create the correct angle needed to drill the disk using the gauge blocks. The next two photos show the hole drilled to reflect the 5.14 degree slant. The last photo has the moon's arbor above the cam clearly showing the correct orbital slant.

This is the first trial fit of the tellurion assembly. Of course, in time everything will be whittled down to size.

These photos show the process of depthing for the 40 plus wheels that comprise this subassembly. Note the microscope eyepiece in the upper center section of the first photo.

Now the process of planting wheels begins. First intersecting scribe lines are etched onto the wheel plates.

Those scribe lines are shown here at 45x magnification. They are 2.5 thousands of an inch or 0.0635mm. The pilot hole drilled is 20 thousands (.058mm).


The build out of the tellurion components continues. At this point a decision had to be made as to the number of spokes the wheels in this assembly should have. So far we have had a mixture of five and six spokes, with six being predominant. In this case I opted for five so as to present as little obstruction to the components behind the rotating armature as possible since a good portion of the complex Grande sonnerie strike train lever components reside there.

In this video we demonstrate the wheel train involved with the two inner planets in the tellurion assembly. Notice how beautifully all the wheels mesh smoothly, even though the top frame parts that should be holding the top pivots of all of these wheels are missing!

Each planetary body in the tellurion must be able to be individually adjusted to the current 'real time' position for initial set up or in the case that the clock is stopped. So each must be equipped with a clutch to allow the operator to move any planetary body at will to correspond to the correct position. The traditional method would have been to use a leaf spring behind the drive wheel of the individual component. In this project the frames are cut out to such a degree that this method could not be used as the leaf spring would be exposed in an unsightly manner behind the delicate frames. So we will employ a concealed coil spring, unconventional in traditional horology, but necessary in this application.

The completed wheel with its hidden clutch is shown by the red arrow.

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