Technology and Function
of the Mechanica M
2
82
83
Depending on their dimensions, the maximum permissible amount
of revolutions of these bearings is about 100,000 per minute. The
fastest wheel in our clock—the escape wheel—only revolves ten
times per minute. We can thus be assured that our bearings are not
being overworked. It is only soiling of the ball bearings—such as
by dust—that will hamper the functionality of our Gear train. Our
movement is, however, adequately protected from dust by its
specially sealed case.
The excellent clock bearings make it possible for us to now work with
less impulse energy as the ball bearings create very little friction, thus
resulting in less loss of energy. Less energy also means less strain on
the toothing, which aids the longevity of the Gear train.
The Friction Created in Individual Wheel-Pinion Meshing
The lion’s share of this friction is determined by several factors:
◊
The materials used, or more precisely, the paired materials
◊
The shape of the teeth
◊
The number of teeth
◊
The size of the individual gearing of each mesh
*
The Materials Used
We use hardened steel pinions
*
and brass wheels in your
Mechanica M2.
This has two reasons:
◊
The teeth of the pinions are often strained due to their higher
number of revolutions and are thus crafted in hardened metal.
◊
The friction created by different materials is smaller than the
friction created by the same materials rubbing on one another.
In watchmaking, the pairing of brass
*
and steel has proven
reliable.
The Tooth Shape
IIn comparison to other technical transmissions
*
, watchmaking
works with high transmission ratios
*
. Making even and low-friction
energy transmission
*
possible precludes a special geometry for the
individual teeth. The theoretically perfect tooth shape for this was
already developed more than one hundred years ago, but could not
be manufactured—neither then, nor now. For this reason, we use a
tooth shape very close to the ideal shape in your clock, whose
individual teeth mainly roll off each other during meshing
*
and
hardly rub one another. We speak of circular arc toothing, which is
close to the ideal of cycloid
*
toothing.
The number of teeth utilized and the size of the transmission ratio are
dependent upon one another.
Time has shown that it is advantageous if the highest number of
teeth possible mesh at the same time. Energy transmission then takes
place very evenly and with little friction. This is achieved by a high
number of pinion teeth. A good figure for precision timepieces is a
pinion with more than ten teeth.
Experience has also shown that a transmission ratio that is too high
results in more friction during meshing
*
. Transmission ratios of less
than 1:10 are considered ideal.
The Gear train of your Mechanica M2 is outfitted with pinions gears
containing 12, 14, and 16 teeth.
The corresponding individual transmission ratios are 1:8 and 1:7.5. It
is only the gear reduction of the Fourth wheel to the escape wheel
that is 1:10.
