The bowl-shaped balance wheel
A unique aspect of the first Winnerl wristwatch release is the implementation of a special balance wheel design originally designed for a Winnerl marine chronometer. A key aspect of the balance design are the angled or bowl-shaped sides, unlike any other wristwatch balance available today.
There are round head screws for equilibrium (A) and crenellated adjustment screws (B) for timing adjustment, both of which types are positioned on the interior of the balance wheel; whereas in a standard balance these screws are all normally located on the balance wheel’s exterior.
The internal placement of these screws and the special shape has several special attributes:
- Because the balance sides are slanted, every adjustment of the timing screw has less effect on the timing result, therefore a more refined timing adjustment can be achieved than is the case with a standard balance;
- The slanted sides also allow much easier access for the watchmaker to make fine adjustments to the timing screws;
- With the equilibrium and timing screws placed on the interior of the balance, the air turbulence inside the watch is slightly lowered from that found in a standard balance arrangement;
- Thermal expansion or contraction of the balance wheel due to heat or cold has less effect on the total inertia load of the balance wheel, because the wheel’s weight spans a cross section of the balance wheel’s radius and is not concentrated only in the wheel’s perimeter
In the animation, we see the change in the speed of the balance when the timing screws are turned outwards in the direction towards the center of the balance; please note that the change in speed of the balance wheel shown here is much higher than reality and has been made solely for the purpose of visualization.