Celestial train demonstration drive, the orrery dual speed transmission - September 2013

This month we begin to fabricate the drive needed to manually demonstrate
the various celestial functions of the clock in both forward and reverse.
This drive is actually a small manual transmission, complete with clutches
and transmission wheel sliding assemblies. What I wanted to accomplish with
this was to have a two speed drive. The first speed, call it "slow",
operates all of the celestial functions simultaneously. These contain a very wide span of time reference. The shortest
duration functions are associated with he perpetual calendar (the day and
date), and the planisphere, (rotating once per day). Next are midlevel
durations (the phase of moon, seasonal changes of sun rising and setting,
the moon's rising and setting. On the calendar there is the month and
season, year, and leap year. Then there is the entire tellurian with
earth/moon and sun system which has a one year cycle. The last are the long
duration cycles as represented within the orrery which has the outer planets
of Mars, Jupiter and Saturn; each having cycles of 687 days, 11.86 and 29.42
years. The ratio between the daily cycle and the longest duration cycle is
10,750:1.
Demonstrating everything together means that some of what is shown in the
orrery is moving quite slowly. So we introduce a second speed. This runs at
a 12:1 ratio. However, at this speed we would easily 'overdrive' all of the
shorter duration cycles. So we disconnect those shorter duration functions;
leaving only the orrery driven by this speed of the drive. The transmission has
three settings. Normal, that is the demonstration drive is disengaged, slow
and fast. We replace the conventional stick shift lever of a car
transmission with a push/pull selector operation to manipulate the five
clutches and seven gears in this transmission. These wheel counts do not
include the external wheels necessary to carry the demonstration power to
the orrery.
As is the case with many other aspects of this project the actual design
of each system that Buchanan is ready to fabricate is made 'on the fly' just before
manufacture. It still amazes me how Buchanan can continue to avoid fatal
mistakes in component placement conflicts, or fatal design errors that are
ever present in a machine that continues to grow organically in design and
complexity from year to year. But as one will see, the space has been all
preplanned in the mind of the maker years earlier even if it had never
actually been designed on paper (see last photo dated April 2009). Below I've devoted some space to show how
the design for this system evolves from a mere thought-schematic, to rough
draft and finally a build drawing.


These four drawings show the initial design concepts. The first drawing
depict the wheel and pinion ratios that are present and then those that are
desired from the drive. The next three are the physical form that these
might take.

Here the design further crystallizes. In the second photo the design is at
the point where the individual clutches and the wheel counts begin to come
into play. Notice the truth table in the lower half of the drawing.
The table indicates which parts of the transmission are engaged or
disengaged at each speed, as well as which celestial functions are engaged
at each speed.

Now the design begins to take on the precision of a design drawing. The
second drawing shows the transmission end-on from the front elevation of the
clock.

Here we have a full fledged 'build drawing'. A cutaway of the ball clutches
are shown as well as all wheel works in their correct profiles. Note that
the truth table has had to be expanded to accommodate additional
complications in the design.

Now we have a close up of the prior drawing after all of the dimensions
needed to machine the actual parts are penciled in. Anyone who has been
involved in the creation of complex structures or the building of model
engines can appreciate the intricacies involved in this type of design
drawing. It requires a different skill set from those needed in conventional
clockwork.

The first two photos show the inner shaft and the sleeve it goes into. The
circular profiles on the shaft and holes in the sleeve will later serve as
guides for the ball bearing clutch work.

Various parts being made for the demonstration drive, mostly the gears.

The first photo shows an exploded version of the transmission shaft. Most but
not not all components are shown, the ball clutch work is not yet made. The
second photo shows most of the gears in the transmission. There is another
complete set of wheel works that come later to connect this component with
the orrery.

The transmission shaft and its related components is installed into the
movement to test for fit and functionality. As noted at the start of this
installment, Buchanan has planned for this drive long before and we can see
a shaft exactly where it is now positioned within the movement as shown in
the next photo taken in April 2009.