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
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.
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.
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.
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
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
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
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.
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
122 and 150 is removing waste material
451 is the embryo moon arm
409 is pressing in the moon bearing jewels
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
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 ½ 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).
I am polishing the main dial frame now.
I thought you may like the way I prepare sandpaper sticks.100% use of
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
(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
The orrery support
structure in its finished state. Note the myriad blued screws.
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.
I have the artwork for the Mars orbit dial complete. It is only ¾ 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.
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 ½ 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.
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
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.