Fabrication of pendulum balance assemblies -
Complete balances, December 2008
Photos show the balance plates continuing to be fretted out. The original
hand drawing is glued to the blank surface and the design is then scribed onto the brass
surface by tracing the outlines with a sharp knife. Then only the areas to be left are
shown on the surface.
Next the actual cutting is done; again by hand on a small scroll saw. The
fabricator can only do about an hour at a time before fatigue begins to sap his
concentration. Remember, one slip and the entire part is ruined! The two plates were,
nonetheless completed in less than one weeks time.
The completed balances are shown next to the original wooden mockup
counterpart. Once again notice how the complexity and delicacy of the final design is a
magnitude of improvement in esthetic appearance from the mockup.
The parts in metal lose the bulkiness that is apparent in the wood
version. Overall length is just under two feet, 61 cm.
Notice in particular how much more delicate the antifriction wheel spokes
and rims are as compared to the plastic painted discs on the mockup part. These parts are
a major, if not the major, visual component of the mechanism. I am pleased with the
Finally the parts necessary to hold the balance springs as well as the
bands that cross between the balances to keep them slaved together are made. I submitted
quite a few photos of what is in the scheme of things a small and insignificant part to
demonstrate the numerous steps necessary to create such parts. First the rough blanks are
created like solders in a row. Various operations like slitting, second photo, and
tapping, next photo are done with the parts attached to the mother blank. This makes
fabrication not only easier, but more precise from part to part. It seems obvious, but a
lot of thought has to go into what steps are taken in what order to avoid costly mistakes
More slitting and other shaping operations. Last photo shows one piece of
the final attachment assemblies.
Initial fitting of the band clamps. Next more tapping operations.
The final part is assembled. The size of this part is just over 3 cm
or 1 1/4". The two knurl nuts are expertly executed. Check the sliding back plate in
the second photo has beveled edges. Normally this would be left with straight edges on
such a small part. There are a total of 8 attachment points requiring eight attachment
assemblies. Each tiny assembly has eleven parts for a total of 88 parts.
First photo shows one of the four attachment assemblies located where the
two balances nearly touch each other and will hold the crossover bands that keep the two
balances slaved together. The second photo is of one of the assemblies that will secure
the balance springs. This design allows one to attach and adjust the springs and cross
bands with minimum effort. The larger knurl performs the adjustment function while the
smaller locks it. Total number of parts for the balance assemblies, 424. Up to this point
we have produced approximately 1750 parts.
The fabricator takes a well deserved look at his creation as it stands so
far and as seen by the reflection of one of the balance spheres.