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Orrery, finish Saturn armature drive wheel set, begin Jupiter gearbox - September 2018




Here Buchanan creates a plastic toothed mock up of the large Saturn transfer (drive) wheel to get a better idea where it will be positioned along the proposed armature.


Buchanan writes: I am working on the pitching of the Saturn arm wheels. I cannot follow the standard procedure of marking out where the wheels must go and then design the frame around the pivots as the arm is such a major feature. So what I did was: made 3 of the 4 gears and finished the first and last and fitted them in place, then place the second small spoked brass gear on a short arbour with a flat pan head. I then glued it centrally on my scribe arm design. That leaves a final gap to be filled with the large wheel. I did a little manual guessing with a pair of dividers to arrive at a diameter that could work and then calculated back to the number of teeth needed. I cut a test gear in plastic and as you can see in the first photo the bearing is in the middle of the curved arm design. There will be another similar size wheel on the top of the plate as well.




Buchanan writes: First photo is of a cheap $60 digital microscope with a built in screen.  The gear that is cutting is 0.3 module, the teeth are 33 thou deep. 1/30 of an inch deep. It saves my neck and my glasses falling off when setting up the cutter to centre height.

Here we see the advantage of modern equipment, in this case where there is the need for a very large wheel. One can see here the early makings of what we call “Buchananization”. The method where an otherwise empty space is filled with a set of, or in this case a very large wheel set. The different design approach we use in contrast to Hahn will become obvious as the Saturn drive wheel assembly is fabricated.




Buchanan writes: The first photo is the largest Jupiter wheel with the largest Saturn wheel. The large gear is 4.3 inches in diameter. It weighs 6.6 grams/0.23 ounces, 44 thousandths inch thick (1.1 mm), 250 teeth.




Buchanan writes: I was a little worried that you might want to go with the rectangular frame design, especially when you think of all the reflections that you would get when it is polished. I also hadn’t thought of the unique design future aspect!


This is a joke based on what I had written prior: “Well that cute wheel makes up for the fact your other one got covered up by the planisphere mask! You know leaving that arm as a rectangular plate would introduce a new design feature...NOT!” I was referring to a large wheel that drove the planisphere mechanism and was a wonderful example of Buchanan’s work, but with the current orrery design we have this now in abundance). See March 2018 instalment.





Buchanan writes: I have been making screws drilling and tapping arbours and general housekeeping . I am almost finished, then I am going to change that frame design for you! Here is my workbench, in a mess before final assembly of the Saturn arm.  The other photos are of various collets and bearing caps that have been attended to today.





Buchanan writes: I spent this morning clearing up two small clearance issues. Then I finished the input gear to the bottom of Saturn, (first three photos) this has a square on the end of the shaft. I made a square punch when I ground the square on the Saturn shaft and drove it through the collet to produce the square hole in the collet.  I am now working on the orbit dial for Saturn.  As soon as that is done I am going to skeletonise the arm. There are 2 more large skinny gears to fit between the Saturn and Jupiter arm. The collet must be easily removable because every time that Saturn assembly is removed it must come off the arbour. I don’t want to rely on only the clamp force of a retaining screw, and, there is not enough space for a pin.

The last photo shows the beginning of the stacking of the planetary arm drive drives. One can see that by the time all of the arms are in place they will completely fill the vertical space.



This video shows Saturn's constant position of its planetary tilt in relation to the Sun as it moves through its orbit. Earth displays the same unchanging position. It is interesting that Saturn's axial tilt at 26.7 degrees is very similar to Earth's at 23.5 degrees. Their tilts, however, are not aligned to each other.



The Jupiter arm will have a similar compliment of oversized wheels but a bit smaller than Jupiter’s due to the fact the orbit is a smaller diameter.



1,514.50 million km (10.1238 AU)


1,352.55 million km (9.0412 AU)

Semi-major axis

1,433.53 million km (9.5826 AU)




Buchanan writes: The table gives us a few facts about the orbit of Saturn. Do you want the distances in Km, Miles or AU? We will use both AU (astronomical units) as well as Km or in this case Mkm (millions of kilometres). AU is found on the main orrery dial. No use for miles as it is not used anywhere else on the dial work, or nearly anywhere else on Earth!





Buchanan writes: This is the basic idea for the orbit dial (first illustration). A knurled bezel like the year dial on the sun/moon dial will help and a better hand. The hand is fixed to the frame and the dial rotates with Saturn that way the numbers always face the reader. This will be the case for mercury mars and Jupiter as well.  Dial size and legibility is the main question, but then most people who seriously examine the clock seem to bring an eye glass!! This is a reflection of the fact that many of the components are on the scale of a pocket watch. The bezel will have what I call a coin-type of knurl similar to that found on the edge of United States coins.


Now Buchanan hand files the curvilinear transfer wheel frame on the vise.



The curved transfer wheel frame is complete. From this photo one can immediately see the difference in the look of Buchanan’s design from that of Hahn’s. Both use the same design mathematically, as well as the same number of wheels, but visually they could not look more different.



The Saturn assembly is seen within the context of the rest of the machine.




Buchanan writes: I have spent the whole morning staring at a computer. I can only place and position one letter or number at a time so it is laborious (first photo of computer screen). I am now working on the codes for the engraving.





Waste not want not. Buchanan uses an old, discarded wheel (see toothed perimeter) as the blank for Saturn's eccentric orbit dial.



Completed engraving for the eccentric orbit dial. prior to silvering.






In the first three photos Buchanan begins the dial pointer for Saturn’s orbital dial. The fourth photo shows the completed pointer with the silvered dial and the coin-knurled edge.



The Saturn subassembly is complete.



This photo shows the incredible engraving detail of the eccentric orbit and degree dials.

The Saturn dial slides neatly along the orrery dial circumference.



Saturn has an eccentric orbit, this dial shows the position and distance of the eccentricity in millions of kilometer as well as astronomical units, AU. The AU is the distance from the center of the Earth to that of the Sun, 149.6 million kilometers. It is a convenient measure of relative distances within the immediate neighborhood of the solar system. The first video shows an initial mockup trial of eccentric dial and the second the completed assembly.




 - Buchanan now turns to the Jupiter assembly -




Buchanan writes: I have decided to dispense with the u shape frame on the Jupiter arm, (first illustration yellow outlined frame). The way that Saturn’s large gears on the arm worked out so well, I think we will get a better looking arm for Jupiter. And gain some clearance space.


I am very happy with the mechanical rigidity of the arms as well as the orrery support bracket. I think the power required to drive this will be hardly felt by the Robin remontoire.



Buchahan writes: I have the basic design for Jupiter all done now and most of the gear sizes are also complete. I will start making the assembly in the same order as I did  on Saturn. First the main pivot point, then the eccentric gearbox and then the moon gearbox. Then I can mount it on the arm with the clearance’s established, and finally, the arm drive gears. The arm drive gears are not as big this time, 3”, but there are a stack of   four and they move at two different speeds.  I thought that Jupiter would not be as impressive as Saturn, but, I don’t think we will be disappointed.


The illustration shows both Saturn and Jupiter in their maximum and minimum orbital positions from the Sun, the aphelion and perihelion. This is accomplished by the eccentric stalk holding each planetary gear box. One can see if one planet is at maximum and the other at minimum orbital distance while passing each other how close the clearance between the two is. The opposite is true when the condition is reversed and the gap opens widely.



This is the gear table for the Jupiter gearbox. Pixilated to protect proprietary data.




Buchanan writes: The top, half cut away, bearings are duplicate as I mirrored them for clearance checking. Deryck writes: The top, half cut away, bearings are duplicate as I mirrored them for clearance checking.




The first parts are cut for Saturn’s eccentric stalk. All of the parts in the first photo comprising the stalk drive work and clutch are assembled in the second photo.






Buchanan writes: I have the planning done for the eccentric gearbox and the gears cut, managed to get one on its arbour. Tomorrow should see it almost complete.  I am working on the body of the eccentric gearbox for Jupiter today. Then onto the main frame for the cluster gear.


Jupiter has a 3.13 degree tilt, not much but I think I might include it as well as we have the moos at that tilt as well. It is the only other planet that we can include it in without a major redesign.  The earth might qualify but we have that in ‘high definition’ in the tellurian




Jupiter's small 3.13 planetary tilt begins fabrication.


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