Continue celestial train demonstration drive, finish transmission, begin
orrery output gearing - October 2013
This month we continue to fabricate the drive needed to manually demonstrate
the various celestial functions of the clock in both forward and reverse.
The first section of this installment finishes the two speed transmission.
The second starts the output gearing.
This month Buchanan has begun to fret out the spokes for the celestial
demonstration drive's two speed transmission. The fourth photo shows the
main output shaft that will connect to the orrery output gearing.
Next we have the associated contrate wheel fitted to the output shaft. The
third photo shows the underside of the plate with another drive bevel wheel.
Both of these wheels are used in the differing speeds for the transmission's
These photos show the action of a ball clutch within the transmission shaft.
In the first photo one can see the inner, beveled shaft within the hollow
tube shaft. Next we see the ball clutch installed. Depending on the position
of the inner rod that ball will either retract or protrude above the surface
of the outer hollow tube's surface. The inner rod is shaped in such a way as
to keep the ball permanently captured at this location. There are four of
these in the transmission.
The first two photos show how the action of the ball clutch will either
allow the sleeve surrounding it to rotate as in the first photo, or be held
stationary as in the second. The next photo clearly shows the machined lobes
which mate with the ball clutch. Next a roller bearing and ring mounting are
In this series of photos the transmission is built up. the last photo has
the end of the transmission shaft protruding out from the front frame. One
can clearly see the inner rod within the hollow tube.
Here the transmission is put into the movement for its trial fitting.
The escapement plate containing the output contrate and bevel wheels
are fitted above the transmission. The vertical arrow shows the transmission
bevel which engages the output bevel located below the escapement plate
(hidden by plate in this photo, but clearly shown in the eighth photo in
this installment). The horizontal arrow points to the transmission wheel
which engages the contrate wheel through a slot in that plate above the
escapement plate, (barely visible behind strike carousel cam). That slot is
clearly shown in the fifth photo in this installment.
We now turn to the next
phase of the celestial demonstration drive, the orrery output gearing. One
could be forgiven for assuming that there
is a simple direct
vertical connection from the output contrate and bevel wheel shaft up to the
orrery. It is, after all, located directly below where the central shaft to
the orrery is planned. However, as is the case with many of the design
features in this project, there is usually a complication thrown in. We need
the output gearing to perform two functions. The first is to reverse
rotation of the final output shaft to the orrery from that present at the
bevel and contrate drive wheels. The other is to obtain the correct gear
ratio for the orrery. The period must be changed from mean solar to sidereal
time. Could this have been done more efficiently? Yes, but certainly it
would not be as visually interesting and beautiful.
The first photo shows a plastic mockup of the gear set proposed for the
orrery output gearing. Five of the seven wheels needed are shown. One
immediately sees the design as bridge raising the wheel set up and over the
adjacent escapement antifriction wheel pair. The mockup allows Buchanan to
check for component conflicts within the increasingly crowded machine. The
next four photos show the mockup placement.
First the rough wheel blanks are cut out of the brass flat stock on the
jewelers saw. Next they are turned into blank gears; the same procedure as
has been done for the over 120 wheels that have already been fabricated.
Next a free-hand drawing is produced for the two cocks that will be used to
suspended the upper wheel set bridge. It reflects the curvilinear ivy style
seen throughout the structure of the movement. Next is a paper cutout of the
proposed fretting for the escapement support plate. Note how much of the
bulk of that plate w
ill be eliminated.
This is the last of the original blocky, rectangular plates comprising the
initial clock frames which were made in January 2010 before the internal
works were transferred from the temporary plastic frames to the permanent
The center photo's circled
area and the red arrow in the next photo show the original escapement support plate made in January 2010 as
described above. This is a good time to look back and contemplate how far
this project has come!
Next the paper templates
are positioned where the final parts will be. Buchanan cuts the escapement
support plate on the same jeweler's saw that has been used on all the flat
stock in this project, including the spokes for all of the wheels,
the swirled escapement wheels and the filigree pendulum balances.
The escapement support
plate is put into position. Notice how this really opens up the area below
to light and inspection. Of course this is then a bit obscured when the
escapement and the associated antifriction wheels are mounted, but more
wheels are just fine by me.
Now the two cocks which
will hold the orrery output drive wheels are cut from brass stock.
Next these are mounted onto the inner celestial train frame pillar to test
for fit and alignment. The two completed cocks and escapement support frame are
then jeweled. Look carefully at the first photo and count the number of
jeweled bearings, there are twelve, plus the eight yet to be installed in
the two cocks and escapement support frame shown in the second photo, more in this one shot than
in a good quality watch or fully jeweled clock movement. But can you tell
the ones that are actual jewels and those which are hiding caged roller
bearings? The answer is there are seven caged bearings and 13 jeweled
Two of the jeweled pivots
close up. Next Buchanan begins the compound wheel that drives the orrery
output gear set. This wheel is both a conventional and contrate wheel; one
mounted on top of the other.
Once again Buchanan has
created an elegant component that is both functional and beautiful.
Buchanan now begins to fabricate the wheel works for the orrery drive. In
the first photo the large cylinders are the blank collets upon which the
wheels will later be secured to. Next the blank wheels are tested for fit.
Next begins the process of spoking the wheels.
Here we see the fabrication of the hard, tool steel pivots for each jeweled
bearing. These are inserted into the end of each arbor. The reason why we
cannot use the common practice of of making this from a single piece of
material is that this movement used stainless steel for all of the arbors.
Stainless is too soft and has poor frictional properties in that it is a
'sticky' metal, entirely unsuitable for bearing material. However, it will
polish to a beautiful finish and more importantly will not corrode. I have
seen too many wonderful skeleton movements that have flash-rusted arbors
because of one unfortunate event where humidity was allowed to become too
great for a period of time. All other silver metal in the clock will also
use stainless, only blued material will use conventional steel since
stainless will not blue properly. It is our intention to run all of these
types of pivots without the use of oil. Dry jeweled bearings are used in
applications where the arbor is lightly loaded and will turn at less than
once per hour. Arbors that have greater loads or rotate more quickly use caged roller bearings.
At this point we are using conventional roller bearings, but for the final
build these will be swapped out for full ceramic bearings which require no
lubrication. These in
combination with the dry jeweled bearings and Harrison's grasshopper
escapement will allow us to make this machine a 'dry runner'. Degradation
and contamination of oil is the number one reason for clock failure over
time. Breguet is reputed to have said in the 17th century, "Give me the
perfect oil and I will give you the perfect watch." What was true then is
still true today.
I know this is
quite controversial; we are breaking new ground here to apply these
principals to a machine of this complexity and mobility, and comments are
This represents the number
of screws needed for the orrery output drive, about 70. All screws used in
this project are custom made, there are no "off the shelf' screws. As one
might imagine the number of screws will reach into the low thousands. Below
are two videos which show in real time how Buchanan makes a screw about 60
seconds a copy.