When you activate the chronograph, you’re engaging the clutch, which is a device that controls the transmission of energy to the chronograph mechanism. The two most common kinds of clutches are distinguished by the direction in which they move, either vertically or horizontally.
With a horizontal clutch, the wheel that turns the main time display’s seconds hand pivots laterally to interlock with the gear that turns the chronograph’s seconds hand. Because one gear is moving and the other is stationary they don’t always mesh seamlessly, which is why you sometimes see the chronograph’s seconds hand wobble slightly when it starts. Also, when the chronograph is running, the drag generated by the horizontal clutch may result in a loss of amplitude that can cause a decrease in timekeeping accuracy.
So why is this design so popular? Part of the reason is that high-end brands like A. Lange & Söhne can mitigate those drawbacks through precision engineering. Another reason is that the horizontal clutch is a beautiful thing to see in action through an exhibition caseback.
What the vertical clutch lacks in aesthetic appeal, it makes up for in performance advantages. Its gears are integrated into the wheel train so they stay meshed all the time. This reduces wear and eliminates the jiggling seconds hand. Also, a vertical clutch doesn’t affect amplitude, so the chronograph can run continuously without causing a drop in chronometric precision.
However, keep in mind is that a vertical clutch’s integrated design is usually more expensive to service. Regardless of your clutch preference, there are plenty of great options out there, whether it’s the horizontal Zenith El Primero 410, or the vertical Rolex Daytona.
Leon Adams is the owner of Cellini Jewelers.