Demonstration selector retrofit - finished, continue debugging
- March 2021
Buchanan continues the debugging process and continues to wrap up remaining
items yet to be completed and finished. One project is the retrofitting of
the demonstration selector. This allows the operator to select the
demonstration of fifty nine complications including the entire celestial train where a twenty four hour period
is shown for each turn of the demonstration crank, and a faster speed to
demonstrate the orrery with an eye toward seeing the outer planets of
Jupiter and Saturn's longer duration orbits, and then back to the normal
operating condition where the clock drives the celestial complications in
real time. Directional plaques are added to the planisphere's
These photos show the
fabrication of the directional plaques that will be attached to the
planisphere longitudinal grid lines: N, S, E and W.
Buchanan tried three different sizes to get the right proportions for
the plaques in relation to the planisphere. Next the final plaques done in
The plaques are positioned for trial fitting before they are silvered.
The next section deals with the partial retrofit and completion of the
demonstration selector assembly. This will allow the operator to perform the
demonstration selection with a key through the case glass via a hole;
avoiding the need to open the case. All routine functions related to winding,
setting of time, striking and celestial demonstration can be performed with
the case closed using a crank or key. This minimizes dust infiltration.
Optimally, the case will rarely be opened.
The original design called for the demonstration lever to be manually
operated from the left side of the planisphere mask. But with the decision
to have a case that would normally remain closed it was decided to eliminate
that hand lever for a rotational key operated through the glass.
If one wants to reset any of the individual celestial objects, the planets
on the orrery, set the planisphere, tellurion or demonstrate the prediction
of a solar/lunar eclipse or adjust the other modules, the case must be open
for the operator to manually move the appropriate objects or setting dials
The first step is to decide where the selector key will be located and
how to integrate it into the existing selector plan where the control was to
be located on the left side of the planisphere mask. Then to determine the
location and shape of the selector dial. Shown here is a color photocopy of
the clock. Given the placement of exiting
components the best location was just below the red arrow and a sector dial
shape would be obvious above.
The first photo shows the fabrication of a ball and socket click detent for
the three positions available on the demonstration selector. A ball and
socket provides a positive position for the gear selector to move within the
transmission, (yellow arrow). Next Buchanan has to drill a retrofit hole for
the updated selector assembly. At this point with the machine assembled and
polished it becomes a very delicate procedure to drill into the frame;
notice the bib below to keep the swarf away from the mechanism.
Here Buchanan performs another set of retrofit machining on a component of
the demonstration drive. Again notice the effort to keep the part protected
from the surface of the machine tool since it has already been through the
finishing stage. Next updated selector components.
The first paper mockup of the demonstration selector dial is shown. We
decided against the word "drive" for the default position of the selector,
that being the clock in the normal position of driving all the complications
in real time for the word "clock" which I had thought to be a bit more intuitive. The
ideal ordering would have been the reverse, with the normative position
being on the left, but the existing components made that impossible. There
are many instances in horology where one does not wind the clock clockwise,
but anticlockwise so this is not a meaningful issue.
The revised selector arbor unit is attached to the clock frame. The next
photo shows the selector dial engraved right off the mill. Using CAD for
dial engraving keeps all of the work accurate and uniform.
selector sector dial done in a French silvering finish, next the dial hand is
The entire selector lever work
Video of celestial demonstration lever.
These three photos show where a bug revealing itself as a tight spot in the
selector pinion push lever. This lever operates within the grooved area
shown by the white arrow in the first photo. A positive side thrust is
provided to that lever by the U-shaped spring shown by the
arrows in the next two photos. This works in conjunction with the three
position detent to be sure that this pinion is always in the proper location
for any of the three positions within the celestial drive transmission. At
first the diagnosis was that the spring was providing too much side thrust,
hence the tight spot.
It turns out that there was nothing wrong with the spring or design. There
was some suspicion that this might be the case because before disassembly
for the finishing process this bug was not there, so it may be a reassembly
error or some alteration due to the finishing process. The latter is
unlikely as these components are quite large in relation to whatever
material would be removed in the finishing stage. One could see how this
could be a factor in the realm of of a small, complex watch.
The answer was the flange of the sliding pinion was rubbing on the collet
screws of the next gear over, indeed a reassembly issue. One can see
Buchanan using a pointer to indicate where this was happening. Real estate
within the machine, as one can see, is tighter than in New York City.
This bug and the photo above illustrates the immense importance of the
debugging process over the entire machine. Look at how much disassembly had
to occur to get at this one problem. The entire center section has been
This is not unlike NASA launching people on rockets into space, if
everything is not working according to plan, there is no turning back. It is
unlikely someone else would be able to diagnose the problem and successfully
reassemble the machine once delivered to its destination..