Tuesday, March 3, 2015

Regulating a mechanical watch cheaply

Regulate a watch cost = computer (you probably have one) + headphones with mic ($15?) + audacity (free)...

Mechanical watches are freaking cool. It's an awesome display of mechanical precision - granted, one that's been around for a while.

A nicely finished mechanical is truly something to behold. A window to the innards can show off the splendor of it's beating heart. The sound of the escapement, smoother movement of the hands compared to a quartz which jumps every second. Just consider how precise these parts have to be to ensure not only accuracy, but so that it doesn't stick, or vary with winding.

Of course, quartz watches are far more functional for the price. They can add functionality much more easily. A change to the programming and a button can switch modes from telling time, to showing an alarm time, to various time zones, a stop watch, and timer - all requiring mainly some code changes. Each hand of a quartz watch can be controlled separately instead of geared together simplifying everything.

Love the details and precision machining of a mechanical. 

It's this precise beauty that generally attracts me to mechanical watches more. The problem is that as a time keeping instrument, even excellent expensive mechanical watches are no match for a lowly cheap quartz. The mechanical's spring varies force as it unwinds, which varies the speed at which it would spin the hands if not for the escapement. The escapement is there to regulate that unwinding. It does so by iterating through halting the movement and then quickly letting it tick - so the time it's halted for + time of a tick is kept close to constant throughout the unwinding.

Of course it's not perfect. Even simple things like orientation - how the watch is lying (face up, on the side etc.) - can affect the timing rate. 

This is a watch I put together. The face, hands and movement from from a Vostok Komandirskie. The case was for an Amphibian. The bezel was aftermarket from another ebay vendor. The Crown was from a much older Amphibian I bought for parts. Something else I got myself into.

I was able to get this watch to ~5 seconds slow per day. Initially it was probably 30 seconds off. Over a week, you're a few minutes early or late. That was too much for me, but common for mechanical watches.

Here's how I regulated my watch. Start by getting the back off. My back is a screw type, so I use the brass wrench tool pictured here to do that.

Let's zoom in and look at the mechanism again. That balance wheel controls how fast or slow the watch is. The slim liver extending down from the balance wheel bearing is the lever to manipulate when regulating the watch. Push the bottom of the lever to the right to slow down, left to speed up (you know directions based on the - and + signs above it).

To "measure" the current timing, I used a simple microphone from a cheap headset. This is flat and rests on the bridge of the mechanism without getting in the movement. You're going to want a quiet room to do this in! (Note to self, test a piezo mic!). I put a container over this and threw my sweater on top to dampen any extra sound (cheap soundproofing!).

Here's the setup - My laptop is running Audacity to record the sound from the mic. 

Here's what the first recording looks like. Select the waveform from the start of the recording to the very first peak. That peak is the tick/tock of the escapement.

My watch ticks at 5.5 per second. So every even second should line up with a peak. Now, skip forward 10 seconds, ensure it lines up. another 10 etc. Here's a minute - and it's looking pretty good. If the peak is happening early, then the watch is fast. If it's late, the watch is slow. The regulating lever needs to be moved ever so slightly to get this accurate. We're talking a hair's breadth here...  

Use the zoom tool as you get closer to your goal. From this shot you can see that i'm recording for at least 2 minutes. Audacity can measure the length of the waveform selected (middle numbers at the bottom). After 2 minutes, my watch is 7ms off. That's .21 seconds per hour. 5.04 seconds per day. So far usage has help up that figure.

Something else to note - depending on the orientation of the watch, the movement can run faster or slower. Generally I don't have much variation with this model. This is a hand-wind movement, so going a little slow is beneficial to me. If I wind it tight and hold it I can make up a few seconds.

Something to note is we are quite dependent on the accuracy of the computer's clock when doing this. Strongly advise that any time keeping applications/services like NTP are disabled during this (if you don't know, don't bother, you probably don't have it). The quartz clock of a PC will be easily accurate enough for this level of accuracy.

So there you have it. Cheap means for regulating a watch. Give it a try :)


  1. Note that it is not your PC's clock that matters, but your sound card's sample clock. I've found that those can be notoriously inaccurate, off by as much as 100s/d. That sounds like a lot, but such an error corresponds to less than 0.01 semitones pitch error when playing back music, and thus generally goes unnoticed. When using a sound card for watch timing, you first need to check it's actual rate by testing a reasonably accurate analog quartz watch.

    1. Interesting. Does the multimedia clock sync with HPET or is it completely independent?

    2. It's completely independent, and is unaffected by, for instance, your PC's clock resynchronizing to time.nist.gov. All the timing information you see in Audacity is in terms of the sound card's sample clock.