and repeat selection levers, & misc. parts, complete strike control
- July 2014
This month Buchanan finishes the lever system which will control the
operations between the clock operating in the normal mode as a quarter
striking clock, also known as petite sonnerie as well as a grande sonnerie
striking clock where the number of hours is struck at each quarter along
with the quarter bells. In addition there is a quarter repeat on demand
function. The full compliment of control levers now begins to take on an
Here is Buchanan's concept for the main control lever assembly drawn upon a
black and white photographic background of the existing movement. This
planning technique has been used many times in the past when Buchanan needs
to see how a proposed component will layout within the existing mechanical
The steel plate will eventually become the slender levers shown on the
rendering above. First the hole that the main lever will pivot on is located
and drilled. The third photo shows how he has left section of metal on the
bottom of the hole to act a collar for the roller bearing assembly. Next a
brass insert is made to secure the roller bearing and this is clearly seen
in the fifth photo. Next Deryck begins to position existing parts to
determine the final contours of the levers.
Buchanan measures where arbors and other extant obstructions exist and marks
them out on a paper stencil, first photo. Next we see those cutouts in the
steel sheet. Note that the sheet is actually mounted to the roller bearing
pivot point, far left, that was previously fabricated so plate’s position is
perfect. The oval cutouts represent the full movement anticipated by this
lever and is demonstrated by the plate positions between the second and
third photos. Further cutting is made to clear other areas like the
pull/repeat crank and levers. Once all of the obstructions are accounted for
the lever is drawn to sinuously curve around them.
Once again we will incorporate our bird
analogue within this design.
The lever is cut out and shown in the first and second photo.
The pivot point is on the same axis as the hour snail.
This photo shows the lever
mounted in place with the context of the rest of the strike levers, quite a
complex area (red arrows). The blued levers seem to stand out better in this photo. I am
still undecided on whether we will blue all of the levers or not.
Notice how the hour snail seems to disappear within the context of the rest
of the clock parts. Likely this as well as the quarter snail and a few other
parts will have their surfaces made to contrast with the rest of the wheel
works within the main frame so as to highlight these parts. The trip crank
lever (yellow arrow) is discussed toward the end of this segment.
Now all the components are mounted to the central rotating point for
the hour snail. First we have the drive wheel which rotates continuously in
step with the time train. Next there is the snail which normally rotates
continuously and is driven by the large wheel shown. However, unlike in a
conventional clock, the snail is also allowed to be partially detached from
that wheel to be snapped into position when the on-demand repeat function is
called upon. Finally there is the strike and repeat select lever which tilts
on this same axis. All of these components need a triple set of nested
bearings shown in the third photo.
This is a
small offset roller part, the repeat select roller, which acts upon the end
of the lever. Even such a small part has jewelling. The jewel also has a
to prevent shock to the jewel surface from contact
with the adjacent lever. The roller rotates with some speed and the
contacting pressure, while moderate still needs protection.
These two photos show a clearer connection between the roller bearing
and the quarter snail component.
Here a rack pin bypass is fitted to the hour rack to allow it to bypass
the rack catch pin when the repeat function is actuated. This allows the
rack to drop to the designated hour when it normally would be held in the
upright position between strike sequences.
A second lever in the
strike/repeat lever system is fabricated. To give perspective, the scale
shown in the first photo is a length of four centimeters or about 1½ inch.
Next the part is mounted within the machine’s strike lever system.
The brass colored part is a safety device to prevent any jamming of
the lever system should one should try to turn the clock’s time hands backwards
(why would anyone do something so stupid in the first place?). This
is currently in plastic to give proof of performance before being made later
in steel. If the snail should move backward, the lever will ride up upon the
snail either tucking inward or extending outward. The normal position would
be pointing directly to the snail’s arbor as seen in the last photo and is
spring-loaded to bring it back into this position. Part of that spring is
the extension seen as the bird's comb, the lever being its beak. That lever
is what I call the ‘rack feeler’; Buchanan calls it the ‘rack reader
finger’, which is what guides the rack upon each step of the snail to set it
up for the proper striking sequence.
The first photo shows the original strike trip lever
prototype in plastic, again in a spray-painted brass color. Buchanan
realized at this juncture that the part needed a reconfiguration from the open
design to a more tighter ninety degree angle. The part is cut by hand
in the same manner as all of the flat stock for this project.
Notice the stepped brass surround for the center jewel another nice touch of
The strike trip crank is cut from the solid and
an arbor collar is fitted. Next it is mounted to its arbor. Next another
lever is fabricated, The watch screwdriver is shown for scale; it is about three inches,
The completed strike trip crank and lever (yellow
arrows). Compare this to the
plastic prototype shown near the beginning of this installment, 16th photo
from the top also with a yellow arrow indicator.
Here we have the final
strike control lever still in mockup form shown in its original plastic and
brass colored spray painted form. First the part is set upon the steel plate
for duplication and then initial hole placements are made.
Next the outline is cut
on a jeweler’s saw and the contours shaped with a hand file. The final part
is seen in the last photo.
Here is where it all begins. This is where the user
manually depresses the lever seen in the foreground surrounding the bell.
The jeweled roller depresses the head of the bird's beak setting in motion
the repeat on demand feature.
A view of the numerous curvilinear strike control
The strike lever work
is now complete. We have now reached a milestone in the project. There is a
complete time keeping clock with petite sonnerie or grande sonnerie and an on demand quarter pull repeat for each function.
Now we move on to the individual complications; that is all of the
associated machinery that goes 'behind the dials'.