By Bryan Bergeron
When I added a second automatic (or self-winding) watch to my collection, I also discovered a new application for robotics — simulating human movement. The great thing about automatic watches vs. traditional mechanical versions is that you don’t need to wind them. That’s fine, until you add a second watch to your collection. It’s a hassle to manually wind and change the date and time and other “complications” on a watch every time you want to wear it. Of course, you could just wear a watch with a quartz movement, or just use your phone to tell time, but let’s stick with the mechanical watches for now.
One solution is to wear one or more watch(es) on each wrist. A more practical approach is to use an automatic watch winder. These machines replicate the swaying motion of the arms by rotating the watch through 360 degrees several hundred times a day. Sounds simple enough, but as in most things, it gets complicated once you explore the details.
Some automatic watches wind the mainspring only when subject to clockwise rotation, while others require counterclockwise rotation. Others work with both. There is also an optimal number of rotations per day for each watch engine or movement. Some movements require 600 rotations, while others require over a thousand. Too many rotations and you’ll wear out your watch. Too few and the spring will run down, and the watch will slow and stop.
Then, there’s the issue of magnetic fields produced by the motors used to rotate the watches. Most automatic mechanical watches are prone to magnetism when operated around magnetic fields, such as those produced by an electric motor. Magnetized watches tend to run faster than normal and require demagnetization — a minor hassle, but a hassle nonetheless.
If you search for “watch winder’ online, you’ll discover a number of models from about $50 and a few well above $2,500 — and that’s for a single watch winder. Double and triple and above, winders cost considerably more. I don’t know what’s in the $2,500 models, but I’ve torn down several of the affordable winders to see what makes them “tick.”
Typically, they’re made with small geared DC motors (like you’d find in any battery powered RC car), a microprocessor, and a few switches to allow the user to specify the number of rotations and directions.
One $50 unit had only an on-off switch with a single setting of 1,200 clockwise turns per day. I ripped out the microcontroller, substituted an Arduino, and now can specify the number of turns, how often, how fast, and whether the rotations should be clockwise, counterclockwise, or both. Instead of a single winding of 1,200 turns, I have my unit set for two cycles of 400 turns, spaced 12 hours apart. This puts less stress on the mainspring and the watch.
Also, when I insert my second automatic watch into the winder, I have a different setting of two cycles of 500 turns, which I found optimum for keeping time.
Watch winders. A simple — albeit somewhat unusual — application for robotics. If you’re into automatic watches, consider the cost savings of repurposing a low-end watch winder or of building one from scratch. SV
Posted by Michael Kaudze on 09/21 at 02:18 PM