I
decided to build
this clock only to reuse and simplify the Anachrone,
for such a good engine deserved to be optimised.
After
several months of prototype
testing I managed to simplify it to the point where one falling ball
was
communicating enough
energy to the
pendulum for
one hour. That's an improvement by a factor of 3599 over the Anachrone.
The rest was mere
implementation...
To be torsion
free the
chassis had to be triangular (a rectangle experiences a 1/100 mm
torsion
per oscillation, which is enough to dissipate the pendulum's energy).
The
height was a consequence of the pendulum's length and the dial had to
fit
in a salad bowl. The materials I picked were steel with some brass as a
warming touch. The pendulum rods are made of invar.
The ball upward movement is achieved this way: a rod pushes the ascending ball through a hole at the bottom of a cup sized to hold five balls. The balls in the cup spread apart then close again behind the ascending ball, preventing it to fall back. The ascending ball pushes on a column of seven balls in a glass tube and the top one falls into a labyrinth of 4 pins and 4 holes, arranged in such a way that in its movement downward the ball pushes the pendulum 4 times in the direction of oscillation. It then comes to rest at the bottom of the mechanism, waiting to be pushed up again when the minutes hand reaches the hour and is detected by an optical sensor. Another optical sensor counts the pendulum's beats and advances the seconds hand.
The
design for this clock
started in May 99 and ran for the first time in November, six months
later.
The accuracy is about 4
second per
month.
"This
one is my preferred
clock because building on the Anachrone it simplifies it to an extreme.
This engine concept gives me a
total
freedom of implementation.
I can now make a clock based on any set of parts: recycled helicopter,
bike or printer parts,
there's
no limit. This
clock is really a step into new territories.
However
I have used few
recycled parts this time, two stainless steel salad bowls, a mahogany
board,
nothing more. The rest was tooled from scratch. So why
recycle salad
bowls? To save time: with my limited equipment, tooling the dial casing
out of stainless steel would have been a two day affair."
About the clock's accuracy
Initially
this clock was
not so much designed for accuracy as for taking advantage of a unique
engine.
My first surprise was that
its operation
was perfect
once the fine tuning was done. The second one, after a year and a half
of testing was that it could
reach an
accuracy of one
second per month or better. I could make it even more accurate by
housing
it in a cabinet but this
would spoil its
looks.
Initially
the pendulum is
fast with a .9999 second beat. It goes faster and faster over 10
minutes,
reaching .999827 s until the
hour ball
falls, creating
the first spike. The pendulum suddenly slows down by 300
microseconds
then speeds up again with
underlying
fluctuations
at one minute intervals. These fluctuations go on decreasing until the
fall of the next ball. The only time
when the beat
is precisely
one second is on the exact half hour. The chart shows no perturbations
created by movement around
the clock
because I was
not in the workshop at the time. Such perturbations can generate up to
15 microseconds beat
excursions.
Every
spike on the graph
is an hour ball falling. Every hour the pendulum's beat varies around
one
second. The overall impact is
a 7 second
variability per
day. This would not be acceptable for a normal clock but
Florence
is designed to accommodate this:
on this sample
the average
beat is exactly one second and the yearly offset 0.0 second. This of
course
is an exceptional sample
because just
moving around
the clock will impact accuracy. With this source of perturbation taken
into account accuracy can
reach 4 seconds
per month. If you have the MicroSet software you can dowload
and view the original datahere.
