Text by Masayuki Hirota (Chronos-Japan)
Just because it's a cam doesn't mean it's bad
One of the fascinating topics for watch enthusiasts is the mechanism of mechanical chronographs. A common topic of discussion is that cam mechanisms are "bad" and column wheels are "good." It's often said that cam mechanisms feel hard and column wheels feel soft, but is that really true? This time, I'd like to explain the truth about cam mechanisms and column wheels.
Cam and column wheel. If you're even a casual fan of mechanical watches, you've probably heard these terms before. They both refer to the type of switch that controls a mechanical chronograph. Pressing a push button controls start, stop, and in some cases reset via these switches.
Simply put, the cam type moves left and right, acting like a toggle switch. In contrast, the column wheel type rotates, acting like a rotary switch. Currently, almost all watch manufacturers that produce their own chronograph movements use column wheels and loudly tout their advantages. They say, "Column wheels are luxurious." However, from a functional standpoint, this explanation is incorrect. In the past, cam-type chronographs were certainly inferior to column-wheel types in terms of functionality. However, since the late 1960s, there has been no longer any difference between the two in terms of functionality.
Cam type
Advantages: High productivity
Cons: It used to be difficult to add brake levers.
Many people cite the stiff feel as the reason why cam-type brakes are inferior. However, this is incorrect. The biggest factor that determines the feel is the stiffness of the spring that regulates the cam or column wheel, and this is the same whether it is a column wheel or cam-type brake. So why is the cam-type brake said to be inferior? The biggest reason is that the old cam-type brakes did not have a brake lever.
A chronograph has three functions: start, stop, and reset. It starts when the clutch is connected to the rotating gear train, stops when it is disconnected, and resets when the hands return to their original positions. As mentioned above, the cam functions like a toggle switch that swings left and right. This allows the clutch to be connected and disconnected. However, a brake, an essential function for a wristwatch chronograph, has never been available.
In the past, pocket watch chronographs did not require a brake. However, as chronographs became smaller and more easily worn on the wrist, a brake function to fix the stopped gears became essential. Without a brake, the hands would move freely if the watch received a shock. However, it was extremely difficult to incorporate a brake into a cam-type watch, which could only be turned on and off.
The solution was Omega's Cal. 861, released in 1968. Designer Albert Piguet added another protrusion between the cams to forcibly apply the brake. Although the braking mechanism was rather rough, it allowed the cam-type movement to have a brake lever similar to that of a column-wheel type. Cam-type chronograph movements released thereafter were equipped with start, stop (plus brake lever), and reset functions. As a result, it can be said that from a purely functional standpoint, there is no longer any difference between the cam-type and column-wheel types.
The biggest advantage of the cam mechanism is that it does not require a complex column wheel. In the past, this part could only be made by cutting, not by pressing. Before the 90s, when cutting technology was not as advanced as it is today, cutting out a column wheel was extremely costly. In contrast, a cam mechanism can be completed by simply stamping out a plate. This significantly reduced manufacturing costs.
