Debugging and timing trials continue, small tweaks are made - August
This month the clock
continues to be trialed. A few small tweaks are made to the planisphere
setting knob, a pawl in the strike train, some improvements in the calendar
module and a decision on the aluminum
The first item was a decision on how to treat the upper surface of the
aluminum base, that portion upon which the clock will rest. Basically the
two choices were black, so that it would match the black top rim of the wood
surround, or a polished surface giving a metallic, shiny and
The wood surround is what hides the aluminum sub base. The 2.5" (6.4 cm), aluminum
sub base is needed to be sure the brass flat bed of the clock has an
absolute flat and solid surface. The brass flat bed frame is made of several
parts, and given the weight of the machine it could flex a bit at the
connecting points. This movement would be magnified by the tall main frames
going out of alignment with respect to each other causing the wheel works to
bind resulting in a catastrophic failure. Except when being moved by a
special device supplied with the movement, it must always rest on this
block. The block has three small feet so it cannot ever rock, no matter the
condition of the table top.
The photos below alternate between the two choices.
This photo shows the unpainted base. It still has machining marks and will
have a better surface for this choice. This is left hand, end view.
This photo shows the same area in black.
A view from the rear.
A rear view with the black surface.
A view from the front in silver.
A view with the black surface. One can see in this photo where the
color of the wood surround comes into play with the painted sub base. But in
the end, the natural silver of the aluminum base was chosen. It gave more
reflected light throughout the machine.
Next the holes for the front glass keyways are drilled in a temporary
Plexiglas that will serve as the front for the mock up case.
Seven holes are needed for the front, four for the winding springs, two for
the celestial demonstration functions and one to set the main time dial. Look
carefully at the four, larger holes, they have a nice brass ring insert!
Even on a mock up one finds perfection.
Area within the yellow circle shows where Buchanan has created a grub screw
to attach the calendar detent wheel. The petal shape, see photo below, is
what makes the year flip instantly and stay in position. Prior to this it
was a tight friction fit making adjusting more difficult should the need
Another view of the screwdriver inserted into the grub screw behind the
calendar detent wheel. Just above one can see the the jeweled detent that rides
on the rim of the detent wheel. This wheel is actually a reused part from
what was to be a part the escapement originally built in
January 2009, but the design was eventually
discarded for another. Nothing goes to waste.
Here Buchanan has added a clutch to the connection of the calendar module
and the celestial drive. Again this makes adjustment easier if one needs to
independently move the calendar module. The first photo shows the exploded
view of the clutch, which is basically a small spring ring with a knurl knob
for tension tightening.
The completed clutch assembly.
First photo shows the making of small screws used to attach the coordinate
points plaques to the planisphere's spider mask. Yes the coordinates look to
be backward, but this is the correct positioning for the planisphere and is
NOT the result of the fact that the clock is being built "down under" in
This photo shows the reworked setting knob for the planisphere. Originally
the knob with a very small number of teeth was permanently in mesh with the
large wheel of 516 teeth. During the demonstration function this would cause
the setting knob to spin very rapidly resulting in a bit of a rattle and was
deemed to be distracting and a possible problem. The solution was to spring
load the knob and its gear to remain out of mesh with the large wheel behind
the planisphere dial. To use the setting knob one needs to push it down.
Buchanan wanted to make an improvement in the 'Strike/Silent' control
spring; replacing it with a pawl. The parts are shown above.
The pawl installed within the strike train to give better performance,