Fabrication of pendulum balance assemblies -
Begin balances, November 2008, page 2
First photo shows rough rod blank being prepared for sectioning into four
parts that will become the balance spheres (shiny rings). Next is initial cutting and last
final rough shape.
First the sectioned off rough blanks next to a semi-finished sphere. Next
a nearly finished sphere just before parting from its mating material. Notice how the
sphere is nearly complete in its surface polish which would make sense as it is
conveniently still attached and mounted to the lathe. Last, finished spheres.
Next six photos show the fabrication of the sphere mounting forks which
will attach the those to the balances.
Finished mounting forks with sphere to the balance. Notice the nice
turning work on the neck along with the taper of the fork as it meets the balance plate.
Another example of fine work reminiscent of the 18th and 19th century master makers.
At this point we begin the fabrication of the balances themselves. Up to
this point I had every intention of having the balances replicate those that were on the
original marine chronometer by John Harrison - H1. This was the only part of this
clock's escapement assembly that was unaltered from his original design. However,
considering the overall curvilinear design of the rest of the clock, and the fact that
balances would be a major visual component of the movement, I decided to as the fabricator
for different ideas. His firm produced several designs, not all of which are shown below..
The first was rejected outright. The straight outline was to be retained. The second
looked too much like a Maltese Cross and was too heavy looking. It also would have
interfered with poising / timing weights that needed to slide align the vertical axis as
was the case in Harrison's original design. I like third and forth design. So why not
combine both! This is what was finally chosen.
Next the chosen design is incorporated into the mockup. The lesson learned
from the pendulum antifriction wheel cages taught us that what might look good on paper,
or even in a reproduction in wood by itself, might look very different when incorporated
into the movement mockup as a whole.
Now the fabrication of the balances begins. The wood filigrees that were
made to be incorporated into the mockup wooden balances are now removed and placed on the
plates to "eyeball" their positioning.
First the location of the balance anchor is determined; where it will be
attached to the inner arbor antifriction wheel plate. Then the perimeter and some
strategic holes are made; then initial cutouts are made.
Further cutouts shown in the first photo. In the meantime we began to look
at the final design for the main balance support frame. If one looks at the initial mockup
we see a simple diamond design. Given the overall mockup makeup, this was sufficient.
However, now that we are refining the design as we go along (making it more fancy!) I
asked for some suggestions. Two designs were submitted below. the second was along the
lines of the original mockup design, with the first more in keeping with the overall
curvilinear frame design. I chose the the first, fancier design.
The balance support was tested in the mockup to see how it fits with
the balance and overall frame design.
The remaining photos show the overall movement progress to date.