Setting the auto wind
system aside and removing the train wheel bridge, we can trace the flow of
mechanical power through the Spring Drive.
As shown above, the
barrel, with main spring, is set at point "A". Notice the jeweled hole for
the barrel arbor to reduce friction. Mechanical energy from the barrel is
transferred from the barrel to wheels "B", "C", "D", and "E" to glide
It's the glide wheel
"F" that is responsible for regulating the time keeping of the watch.
The glide wheel
(above) is not to be confused with the balance wheel of a conventional
mechanical watch, it is totally different. Instead of oscillating back and
forth under the influence of a hair spring, it rotates constantly, and
silently, in one direction at EXACTLY eight revolutions per second.
The glide wheel provides constant stability and
permanency of rate which are major improvements when compared with a
conventional balance wheel.
In order to be
controlled to such an exacting speed of rotation, a pure iron stator (a
strong permanent magnet) "A" (above) is fit to the glide wheel.
The stator serves
several roles in the operation of the Spring Drive movement. First, upon
initial start of the watch, the glide wheel (and stator) is allowed to
spin freely for one second generating enough electrical power to energize
the control circuit. After initial starting and the control circuit taking
control of the watch, the stator acts as a brake to regulate the glide
wheel's speed at eight revolutions per second. If it wasn't for the
stator, the glide wheel would spin freely at several thousand revolutions
per minute (and time would really fly!) The stator also sends one pulse
per revolution to the control circuit that indicates the exact speed of
the glide wheel, allowing eight corrections per second if required.
Removing a few more
components we can see the control circuitry (above).
The glide wheel, with
stator, is positioned at point "A". Two coils "B" surround the stator,
without touching it, Seiko improved the
performance of these coils by developing a method for winding them
especially tight and even. These coils, combined with the stator, serve
two purposes: acting as an electronic brake to control the glide wheel
speed, and generating the minute amount of electricity needed to power the
control circuit "C." It's the control circuit that is the brain of the
system, via feedback from the stator, dictating when the glide wheel
should be slowed slightly or allowed to spin slightly faster.
I suppose we could
say that the stator, coils, and control circuit are the cruise-control
that keeps the glide wheel rotating at exactly eight revolutions per
second, and marking the time within 1 second per day!
A small window offers
a nice view of the glide wheel. Notice the sharp beveling of the plates
and bridges. Although the beveling is done via machine, it adds a crisp
flavor to the watch.
For comparison, the
upper row of parts above are the major components of the Spring Drive,
while the bottom row is that of a conventional mechanical watch.
The Spring Drive has a power reserve of 72
hours, about 24 hours more than most single barrel watches. A series of
gears transmits the power information from the barrel to the dial.
Continue to Part 3 of the Article
Return to Part 1 of the Article