Dr. N.
What does aerodynamics have to do with refined precision watchmaking? And how can the shape of a component interfere with the flow of air to the point of altering the gear of a mechanical movement?
We learned in the previous article the reasons for the choice to opt for a free spiral balance wheel accomplished by Patek Philippe and Rolex in the mid-twentieth century. Here we see in greater detail the technical choices of these two houses symbolizing luxury watchmaking.
Let's discover together the curious story of how the work in an unusual context by designers and engineers, towards the middle of the last century, led to innovations still on the crest of the wave. The protagonists of our story are two heavyweights in luxury watchmaking: Patek Philippe and Rolex.
The Patek Philippe Gyromax
To further refine the accuracy of the outrigger, which is the regulating organ of the clock, Patek Philippe focuses on aerodynamics. Why do you choose to focus on an apparently marginal aspect? The balance wheel oscillates at thousands of alternations per hour. This results in a considerable tangential speed of the outermost part of the balance wheel: the presence of protrusions in this case has an impact on aerodynamics.
A further advantage of the solution adopted by Patek Philippe, called Gyromax, is the greater compactness of the adjustment system: it does not affect the external diameter of the rocker. This design choice makes it possible to create a balance wheel with a larger overall diameter, thus ensuring greater precision - the larger the balance wheel, the more regular the oscillation will be.
Patek Philippe's free spiral solution: the Gyromax balance wheel
Il Gyromax by Patek Philippe it works by slowing down or accelerating the march of the barbell thanks to the rotation of the weights placed on the perimeter of the bar. When the hollow part of the weight - the cleat marked in white in the schematic image below - is turned outward, the weight is concentrated closer to the center of the bar. Like a skater crouching during a pirouette on ice, the bar will find itself spinning faster, due to the concentration of mass near the center of rotation.
The reverse is true for the case in which the weight is rotated with the hollow part inwards: this is in fact equivalent to increasing the diameter of the balance wheel and reducing its rotation speed.
The Rolex Microstella balance wheel
Also Rolex, almost a decade later Patek Philippe, adopts the free spiral balance wheel. The solution chosen by Rolex is the so-called system "Microstar". Compared to the flat weights of the Patek Philippe Gyromax, Rolex Microstella it is characterized by a construction closer to the traditional one of the free-spiral escapement. Also in this case, in fact, the balance wheel is equipped with screw weights mounted on the perimeter of the balance wheel, only, unlike the usual free spiral solution, here the weights are mounted along the inner part of the circumference. This choice results in better aerodynamics - although not at the levels of the Patek Philippe Gyromax - and a smaller external dimensions, so that a larger balance wheel can be created without the adjustment weights interfering with the movement.
To adjust the barbell Microstar di Rolex a special tool is used, which screws or unscrews the weights, bringing them more or less far from the center of rotation and, thus, slowing down or accelerating the movement of the balance wheel.
Rolex and Patek Philippe, innovations compared
Both escapements adopted by Rolex e Patek Philippe they present themselves as valid improvements to what is already a refinement in watchmaking, namely the free-spring balance wheel. Choose the most aerodynamic and refined solution Gyromax di Patek Philippe or that you opt for the Microstar di Rolex, more similar to the “traditional” free spiral system, you still fall on your feet: both cases are technical solutions of undoubted validity.
