Balance diagonals, poising weights, strike train rear frame, begin snail transfer train -
This month Buchanan begins on the pendulum balance diagonal braces. These
are necessary to stiffen the large, intricate diamond shaped frames and also supply an
area for the balance's poising weights; similar to the design in Harrison's H1 marine
chronometer. First a drawing is produced to show parts that will secure the diagonals to
the existing balance arbors. The following photos show these parts being fabricated with
the main arbor attachment structures outlined on the raw brass stock in the last two
These photos show the parts that will secure the diagonals to the frames
themselves. These are made in split halves. They must clamp around the upper and lower
center upright of each balance. The last photo shows one of these in place before final
closure of the part around the upright.
Next the diagonals are fabricated. First the raw rails are cut from brass
stock. Notice how we do not settle for a simple profile, but chose to have decorative
ends. This requires the entire center section to be reduced to allow the larger decorative
flares below the end holes. The last two photos show the diagonal attachment parts in
These photos show the diagonals in place. Considering the density of the
components in the movement it's amazing we were able to find the free space necessary to
allow for the sweep of the diagonals.
Now begins the fabrication of the poising weight discs. We decided to make
these in keeping with Harrison's original design as depicted by the background photos in
the last two shots.
The poising weight frictional supports are made. The rough blanks are
made, drilled and sliced. Another set of custom screws are made (most for other parts of
the movement). When the screws are loosened from the rear plate the weights can be moved
along the the diagonal rail to achieve the ideal balance of the pendulums.
The weights are now in place. B decided to blue the steel base in addition
to the screws. We may later change to a polished steel surface for the plate to give
contrast, but this is to be decided later. The last photo shows the upper balance weights
The rear strike train frame is now fabricated. Notice how the movement has
taken on a more vertical 'feel' from that shown before. it's slimmer and more refined. The
large blued screws are a taste of what's to come when all the screws are done in this way.
A milestone is shown here. For the first time we are beginning to place
and shape the dials for the movement. Shown here are to the left, the main time dial and
on the right the tellurium.
The design of this movement required that the information pertaining to
the the strike train snails be transferred from the left hand side of the movement (as
seen from the front) where the time train resided to the opposite side where the strike
train was. Therefore, a set of idler wheels would transmit this information across
the rear of the movement. Needless to say, of course, the extra wheels were a welcome
extravagance! The striking mechanism will be a quarter repeater. The first two
photos show the wooden mockup of the idler wheel train and frame. Another very
important milestone is shown in the third photo. Here we are inserting a wood mockup
system into the actual metal movement instead of into the wooden movement mockup for
evaluation. The actual movement is now far enough along that the wood mockup is no longer
needed. Look carefully at the last photograph. the transfer wheels pass through
the area bounded by the pendulum horizontal frames and the diagonal braces! As B said to
me, "I want someone to look at some particular feature of my work and ask, 'well now
just how did he do that'?"
This series of photos shows the modularity of the movement design. The
lower frame containing the heavy main frame and wheels is separate from the upper
three frames. These are divided roughly between the time train the celestial train and the
strike trains. This design makes assembly and more importantly, future servicing much more
easier than would be possible in a conventional plate and spacer design.