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Orrery, complete inner planets gearbox  - April 2019




The upper bridge in connection with the Earth rotation is fabricated in the six photos above. Buchanan chose to make this out of stainless steel to give a color contrast and shaped it in the same manner as was done on the strike train epicyclical fly fan cages back in December 2010.

42 parts were needed to make the Earth / Moon armature. However, we encountered one of the rare events where a design mistake was made. The Earth rotates in the wrong direction. It would not look good to see it turning clockwise while the Earth on the tellurian was turning counterclockwise! An additional idler wheel will need to be squeezed in to correct the direction.

A view of the completed assembly. Next Buchanan begins the correction to the Earth’s rotation. He gave the bridge a rounded, sculpted look like the frames on the strike train fly fan cages.

Buchanan writes: This is what I am doing.  I have cut a new large 91 tooth wheel that is just small enough to miss the teeth on the earth pinion, you can see the gap (first photo). The new wheel is under the old. Sorry bad photo, (second photo). Then I am going to add an idler wheel to change the direction. It is the small solid wheel and I can make a small cock to carry it; that matches the design, (third photo). I can just squeeze it in to some dead space.

This is a little like building a new door to get out and hoping the architect does not notice.



Buchanan writes: Here is progress today. I have the idler fitted. (First and second photo) is the new idler and its arbour. (Third and fourth photo) is the new bridge the bridge and idler gear assembly is adjusted to mesh and run smoothly held with the clamp. Then I drill the steady pin holes and fit the pins.

Tomorrow I will get rid of 95%of the excess material.



Buchanan writes: 20 hours and 12 extra parts and we are going again. I am now cutting the big arm idler gear.

The Earth / Moon armature consisting of 54 parts is mounted to the rest of the inner planets gear box.

This video shows the revised Earth /Moon system showing the correct counterclockwise Earth rotation.

At this point a milestone has been achieved – the last wheel is cut to mechanically complete the machine.


Three wheels of slightly differing size needed to be made to get the correct fit where the diameter will give the right mesh with the center axis exactly where it needs to be on the center of the armature. The transfer wheel is positioned on the Earth / Moon armature. This is the last wheel to be cut in the project.


The first photo shows the last wheel being cut on a computer-controlled mill. To the right is a video magnifying camera showing a close up of the teeth as they are being cut. A mirror was set up at a 450 angle to better see the camera screen from the front.

The last wheel is cut in this project on April 5, 2019. This makes for about 500 wheels in the machine. The first wheel was cut on December 30, 2006, see below.


These photos were taken on December 30, 2006. This was the first wheel cut in the project one of four main winding drum wheels and was done on a manually operated lathe. The remaining three rough blanks are seen in the second photo, over a dozen years ago.


The first photo shows the depthing process to accurately position the transfer wheel center on the armature. Second photo, the transfer wheel has its collet attached and is now made a part of the Earth / Moon armature.



Buchanan writes: Here is the construction of the gears for the moon phases (photos in order of explanation).

740 is depthing the gears, first photo
315 is drilling the gear centres, second photo
122 and 150 is removing waste material, third photo
451 is the embryo moon arm, fourth photo
409 is pressing in the moon bearing jewels, fifth photo
940 is the centre idler wheel. Sorry no spokes here. Sixth photo

I think this is the smallest gear cut in the project at about 1/8” (0.25 cm). It is ironic that the last wheel fitted to the project is the smallest while the first wheel back in 2006 was the largest at just over 5” (13 cm in diameter).



Buchanan writes: I am glad you don’t mind the lack of spokes. The wheel is 1/8th inch diameter once the depth of the teeth is removed and a jewel inserted there is just no space left.  

This ‘complication’ is also lacking in the Hahn. So it is a surprise extra, be it rather small. It is rather interesting to compare the earth mechanism on Hahn to ours.  His looks rather agricultural, I still have the greatest respect for Hahn when you look into the basic design. To be honest, if one looks at Hahn’s entire orrery it looks crude by comparison, but then he was working with tools available to him in 1780!


The completed Earth / Moon subassembly and installed into the inner planets gearbox.



Buchanan writes: I had a pair of ball races that had a little play. Almost nothing but it allowed a gear with very little clearance to jam another small gear and I stripped two teeth. Now this sounds real bad, but when I came to recut the broken gear, I was checking up on my dimensions because this gear looked like it was meshing a little shallow as well. See (first two photos) you can see the broken teeth opposite to the teeth the small gear meshes with. Compare how thin they are as well to the new gear in 454.

Well it turns out that the gear was the wrong size. I must have dropped mm on my micrometre somehow.  I have removed the slight slop in the bearings so the play will not reappear and the correct size gear won’t be able to crash in any case.

Next is a very delicate machining process (third photo). I had to counter sink two screws and I didn’t want to disassemble everything. All went well. I have also reduced the planet arms where I have marked the black, as they are still too heavy and plenty strong, (fourth photo).





Buchanan writes: I am polishing the main dial frame now.

 I thought you may like the way I prepare sandpaper sticks.100% use of sand paper.

Ice lolly sticks (Popsicle sticks) are glued to the sand paper and then cut with a Stanley knife on a scrap piece of glass, (first four photos). They are chamfered or cut into thinner sections according to the job, (next two photos).

(Last two photos), are the difference between the parts off the mill, upper parts, and when polished, lower parts. You will notice that there are no radii on the inside corners.

As soon as this section is polished I will carry on with the small eccentric orbit dials.



The orrery support structure in its finished state. Note the myriad blued screws.



Buchanan writes: I am working on the inner dials, I found an interference between mars and Jupiter, I can remedy it reasonably simply as it is a height interference,  it is primary caused because, when I introduced Jupiter’s tilt and didn’t take into account the dial clearance required. It also looks a little worse than it actually is because Jupiter is not properly screwed down onto the eccentric gearbox. I will fix this before I continue with the dials. The third photo shows the clearance issue resolved.


Buchanan writes: I have the artwork for the Mars orbit dial complete. It is only inch in diameter so space is very tight. But look at the beautiful detail of the engraving, even at this small scale.

I don’t think I can fit in the words Aphelion Perihelion and Semi major axis as well as the numbers. 

I will engrave it now and check the results. The numbers are less than 1/16th high as it is.  The Saturn and Jupiter dials have the words and the basic dial layout is the same so I think the information is displayed logically for Mars and Mercury.



Buchanan writes:  This is what I am thinking about for the earth dial (second, third and fourth illustrations). I can place a small inner hand on the earth arbour to indicate hours and an outer hand on the moon arbour to indicate the phases. I thought about a 1 to 29.5 numbered dial, but, this dial is so small (less than inch) that the age of the moon numbers would be minute. We also have two other 29.5 dials. One, a band around the moon on the sun / moon complication (the Halifax style Moon), and, also the sidereal month dial on the Tellurian. I chose the second option.

I will also colour the moon phase circles so the ring at 24 will be solid black while the ring at 12 will just be an engraved circle. The others will be partially coloured.  I have a centre half circle in the chapter ring to show hours of darkness.

We could number the dial as two 12 hour sections. This was the choice.


Deryck writes: I have the Mars and Mercury dials completely engraved so I will continue to finish and fit them (two photos above). I was looking at some of the other small silvered dials on the tellurian, and, I am convinced the where ever I can fit one in, they will all get knurled bezels. 


The orrery is now mechanically complete. It is the last module (complication) in this project. The remaining items are purely decorative: name plates, base dials, and semi-precious stones and their blued support wires for the planets, pearl moons and Sun. All of these have to be left for the final assembly as they must be in as pristine condition as possible.

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