Finish Saturn gearbox, begin Saturn drive wheel set
As explained before, space in the planet gearbox
assemblies is very tight. Buchanan writes:
Today I ground down ten 5mm diameter jewels to 2mm diameter for the bearings
for the cluster gear.
The jewel is glued onto a 1mm diameter spigot and then spun round in two
ball bearings mounted in the T shape aluminium block (first photo). As diameter is very
critical, I twisted a long coil spring onto the end of my “grinding arbour”.
This gave me a drive with no up or down force. Using this method I could
grind the diameter to within a 0.0001 of an inch. I made a few spares
as well. Tomorrow I hope to start cutting gears.
The first two wheels are cut. In the next photo the tilt is fixed at the correct 34°
to the eccentric orbit bracket and
the rough eccentric gearbox allowing for an elliptical orbit is seen.
A setting clutch is also needed to be devised that will fit within a 1.5mm
space for the moons.
First cluster gear mounted.Level one.I needed to
shorten the jewels as this gear is long enough to fit two jewels into. I
will now start to work my way down the two sets of gears. I think I will be
able to thin down the plate thickness as well before we start to fret a
The second photo shows the accuracy achieved
by the measurement of the micrometer. This incredible amount of jewelling
work is the result of our design decision to not have any conventional
pivots; that is no steel pivots in brass pivot holes. Only jewels or ball bearings for the holes.
Even at this size this small wheel is fully spoked out with six arms and
weighs in at just 0.5 g (0.176 oz.)
I have the first gear finished and working on the
next set that drives it.I worked
through the relevant angular velocities of the gear tubes and found some
moons in rev./day
Days to make 1 rev. in
relation the next moon
Just for comparison, a second hand makes 52,560 revolutions/year, 5,256,000
in 100 years. A minute hand makes 8,760 in a year and 876,000 revolutions in
I’m confused by your chart. The difference between moon in revs/day is
identical for moon 1 and 2, how is this possible? Also in revs/year both
moons 1 and 2 are the same, how can that be if the revs/day are 0.52 and
0.37? Am I missing something here?
It does look confusing, that is why I sent it to you. I am looking
relative speeds, or the difference in speed, between each tube to see how
much each tube rubs, or will wear the next. The first column is how many
days it takes for one obit around Saturn. In the second column, I convert
it to how much of a revolution per 24 hours. Then I subtract the moon 1
from moon 2, moon 2 from moon 3 and so on, in column 2, to get the
difference in portions of a revolution per day between each moon. Then I converted it into round numbers for comparison, So moon 1 takes 1.9 days
for an orbit. Moon 2 takes 6.6 days to be lapped or overtaken by moon 1.
Moon 3 takes 6.6 days to be overtaken by moon 2
So for moon tube 1 to revolve inside moon tube 2 for one revolution takes
6.6 days, and, moon tube 3 takes 6.6 days to revolve around moon tube 2
because moon tube 2 is already spinning,
In the first photo we see the trusty jeweler’s saw
spoking out a wheel. Next the staking tool is used to secure the pinion to
Fitting all the wheels on just two arbours is not as easy as I thought. I
have had to recut two of 6 wheels so far to make them run smoothly. In photo
306 (last photo) I am testing the next set in the frames to make sure that
they run freely. I had to cut the teeth in the smaller of the two wheels
another 0.1mm deeper as they were just stiff.
We now have 4 sets of gears out of 9!Level four.
Photo 1 is preparing the blank. Photo 2, teeth cut. Photo 3, testing;
meshing. We got it right this time. Photo 4, staking the gear
onto the pinion. Last two photos, the finished result.
I write in response: I really like the
last photo. Again your work surpasses those who would (as did Hahn) skip the
spokes. Once the plates are fretted out this dainty subsystem will be a gem.
Buchanan writes: Here is level 5. Just more of the same good things. I am
really impatient to see what this will look like when the frames are
It is interesting to see how much photography has improved since you first
posted that page on the Dent. It looks even better.
(Here Buchanan refers to a Dent
exhibition clock I purchased from an auction of the objects in The Time
Museum, Rockford, Illinois in 2002. I had updated the poor photography that
I had done at the time with better images. There were several ideas I had
used from this clock for this project including bronze colored metal for the
larger wheels, alternate click action for the click springs, vertical arbor
fly fans for the remontoire, and most important the Wagner style
gravity-driven rocking frame remontoire.
Buchanan writes:Level 6 is complete. These photos (first
and second) show the temporary bushes I make as soon as I have cur the
gears, so as to check the depthing. The bushes in the test are only to
replace a collet or a jewel to run it on the arbour to test the depthing.
Here we have the
smallest wheel in the orrery so far. Look back on the orrery we used as our
design model made by Philip Hahn and see how nearly all of the wheels he
made were left as solid disks, only the idler wheels were spoked, and these
as a simplified four spoke design.
Notice the jewelling on
the ends. Buchanan writes:Level 8 is complete. One more layer to connect to the
bevel gears and this set of gears will be complete. It is nearly monotonous,
if I wasn’t watching the assembly build up.
In this photo the pair of gear trains are all unravelled from a stacked pair
to a lineal view.
Here is the gearing finished. Next is the dial and pillars in the rough and
then the moon arms and clutches. I have to fit 5 clutches to fit into 8.75mm
of height, from the top of the inner moon arm to the bottom of the outer
Here is a photo of the start of the moon arms, the blanks, marking out and
drilling the angled hole for the moon wire, (first three photos). I
have some thinner spring wire on order. What I had was too thick. It may
delay me a little as it must be spring wire and also be straight and blue
well. I may use a bit of temporary wire to be able to place the Saturn
gearbox properly on the arm so that I can proceed with the next stage.
last photo shows an exploded view of the tiny clutch system for each planet.
The disk with the hole in it is the rough blank for the moon mount; the hole
is where the wire will be inserted as the stalk for the moon.
will later be milled down to a decorative arm. The two
small rings are the compression clutch spring and clutch face ring. Next is
a threaded flange which screws onto the end of the moon tube.
Here the parts are positioned on the moon mounting disk, the second photo
showing a match head for scale.
In the first photo the compression spring clutch is inserted into the
ringed recess in the moon mount. One can see the spring rise above the edge
near the 6 o'clock area and the clutch ring next to it. Next the clutch ring
is place on top of the compression spring. Later a screw on flange piece
will compress and hold the spring clutch assembly together. There will be
five of these, one for each of Saturn’s moons.
These illustrations are
the artwork for the top and bottom plates of the Saturn assembly. Buchanan
now turns to the artistry of dressing and decorating of the Saturn gearbox
the fun part of this process.
The plates for Saturn
are now skeletonized. The first photo shows the separable ring bearing used
to stabilize the five concentric moon tubes
The Saturn assembly
contains nearly half the same number of parts as the pocket watch and
illustrates the scale of the planetary gearboxes. The last two photos show the lower and upper Saturn frames.
Here is a short video of a manually guided machining operation on one side
of the Saturn eccentric bracket. It was quicker to do it this way than
to write a CNC program.
These four photos show the eccentric gearbox being refined. Notice the
bevel drive wheel to match Saturn's
planetary tilt to the ecliptic. Most other makers, including Hahn simply
used regular wheels meshing at this angle. Yes that way works, but it is not
the best way.
The dial ring for
Saturn is fabricated. The first photo shows the advantages of using computer
aided design for engraving. The second photo shows the computer aided
machining. The engraved blank as originally engraved is shown with the
initial black wax to show the detail, third photo. It initially appears a
bit crude to our standards. The engraving is created using a fine tapered
tool. But Buchanan purposefully engraves the dial deeper than necessary so
as to be able to later mill the surface of the dial revealing the finer
detail a few micro-millimeters below the original engraved surface from the very tip
of the tool to give the fine detail in the last photo.
The frame pillars are now decoratively turned.
The Saturn assembly is complete except for the plain dial ring which will be
replaced with the engraved piece shown previously.
Notice the ferrules at the base of each moon stalk, another incredible
attention to detail that Buchanan lends to his creations. The moons as well
as Saturn are still just plastic mockups at this point.
The Saturn gearbox rotates Saturn and revolves five moons. This is the first
component in the orrery for the astro-skeleton clock. It is based on a
design by Philipp Hahn, 1780. Only five moons were known at that time.
Buchanan now turns to the armature and drive train of wheels from the hub of
the orrery to the Saturn eccentric gearbox which in turn will drive the
These photos show the tight clearances facing the outermost planet. The most
critical area is on the rear side, first photo, between the Saturn assembly
and the rear support bracket for the pendulum degree arc dials (beat plate).
Look closely, the outermost pillar supporting the dial ring was removed to
make the clearance.
(First photo) is the basic design
for the Saturn main arm. The reason for this is that I need to know where
to plant the gear arbours. There are still add ons for dial mounts and so
on, to be added to the design.
This design works in our favour. In (the
second photo), you will see that the next small gear out from the main
arbour, is set to one side, pen is pointing to it, to enable its bearing to
be in the centre of the curved arm. This makes the next gear somewhat
larger in diameter , it will be over 4 1/2 inches in diameter, the plastic
ring gives some idea of its size. Now imagine another gear the same
size but below the arm and staggered because I put the small gear next to
The other(four)photos show a double sleeve gear that transfers motion from
Jupiter to Saturn.
I decided that I need to make all the Saturn gears before I move on to
Jupiter, as they affect quite a few other dimensions. The next assembly is
the 4 gear coaxial shaft assembly that allows the feed to Saturn’s moons to
get under the eccentric orbit gears and also the Saturn arm (last photo).
Today I started on the lowest set of gears on the whole orrery. It is the
fixed gear on the main armature and its drive that keeps Saturn facing the
same way all the time, (first photo).
Then I made a bearing bracket. This supports the outer lower gear, (next
This drives through the middle of the assembly (first
photo above), the assembly brings the drive to Saturn’s moons through
the plate. And we take the orbit drive up through the middle of the assembly
(second photo). Tomorrow will be
a tidying up day for this section before I move on to the drive out to the
end of the arm.
One can see that as the
wheels are fitted space is tight. In the first photo the bearing collet
flange had to be countersunk to accommodate the adjacent wheel. The second and third
photos show the wheel assembly to date. Next 130 screws are made, 100, 1.4mm
and 30, 0.09mm, another busy day.