You heard one, I heard five

One tick of a mechanical watch actually consists of five sounds. Let's hear it in detail

October 2, 2023

You read it right, that you heard it wrong! 

Well, maybe it is safe to say that we all hear only one sound during a tick or a tock. As it's not possible to hear those sounds distinguishably just with bare ears. But if you are a watch enthusiast, a horophile, then you should know where those five sounds occur. 

In case you're unaware or maybe someone who's not into watches that much and is rather a curious reader, there's something you need to understand first. That is the basic working principle of the Swiss lever escapement. 

During the mid-18th century, in his workshop in London's Fleet Street, English horologist Thomas Mudge invented the lever escapement. It was arguably the greatest innovation in the history of watchmaking. It was both reliable and accurate, compared to earlier escapements.

Animation lever escapement from Wikimedia Commons
Animation of inline lever escapement, showing motion of the lever (blue), pallets (red), and escape wheel (yellow); courtesy of Wikimedia Commons.

Over the following years, several renowned horologists such as Abraham-Louis Breguet and Peter Litherland made improvements on the lever escapement. By the 19th century, this became a staple in Swiss watchmaking and the Swiss-redefined version got the name of Swiss lever escapement. From then onwards, virtually every mechanical portable timepiece has this escapement either in basic or in some modified form. 

How does it work? Well, it's pretty simple and yet ingenious. But explaining it in words would make this post rather long and boring. Instead here's a small video that explains things very nicely and in detail. 

Now that's out of the way, let's hear about the five sounds. And for reference, I'll be using the same terminology as the video above. 

Say at some point the impact jewel is rotating clockwise and moving towards one of the horns of the pallet fork. Once it hits the pallet fork horn, that would make the first impact sound. 

This results in the movement of the escapement wheel — one of the teeth of the escapement wheel slides under the locking face and hits the impulse face of the exit pallet. When the tooth unlocks from the locking face, it makes the second sound.

As the club tooth of the escapement wheel continues to slide along the impulse face, the cam action translates the rotary motion into linear motion and pushes the exit pallet upwards. Which turns the pallet fork about its arbour, forcing the other horn of the fork to hit the impact jewel. So the club tooth escaping the edge of impulse face creates the third sound and the horn hitting the jewel does the fourth one. 

Finally, the pallet fork hits one of the banking pins, making the fifth sound and completing one tick. In reality, all these hits and their sounds happen in such a minuscule timeframe, that we can hear only one sound — a tick or a tock. 

Talking about tick-tock, do you know what happens to a timepiece when the tick and the tock take different amounts of time? Well, that's a discussion for a future blog post. Until then, keep ticking!