What is old...

Circling back to our Waltham 12s and classroom exercise. 

After removing the mainspring from the watch it was time to remove and examine the balance wheel. The balance wheel is the most complex part of the watch. 

In his explanation of the function of the balance wheel, Master watchmaker Dave had a huge, electric-motor-powered model of a watch escapement for us to learn from in the classroom.

What is an escapement? 

I'll try to be brief.

A watch has components for several different functions. You pull and twist the crown and stem mechanism to turn the hands to set the time and to wind the watch mainspring. There is a wheel train to transfer the power of the mainspring to the hands and other parts of the watch.

And the end of the power train is the heart of the watch, the time regulating components, collectively called the escapement. 

Power from the mainspring is passed along the train of the wheels and terminates at the escape wheel. The escape wheel (and whole wheel train) would spin freely if not limited by the action of the pallets and the balance wheel. As an escapement ticks, the balance wheel spins back and forth, engaging with and pivoting the pallet fork which meshes with the escape wheel. Each swing of the balance wheel and allows the escape wheel to move one tooth forward. 

Tick.

My belief is that unless the reader is quite experienced in the details of timekeeping, this description, no matter how well elaborated will not suffice in elucidating the subject to clear comprehension.

Uh, what did you say Professor?

Sorry. 

It certainly took this horological fan a long time to really grok how an escapement works.

The graphics of the mechanical watch movement at Animagraphs would have sped my learning dramatically had I discovered them sooner. 

They are sensational.

See this graphic animated.

And Dave's escapement robot monster was a wonderful learning tool as well.

The balance wheel of our 12s is constructed virtually identically to those in most watches. It is removed as a whole unit by unscrewing the balance "cock" which is the bridged plate that holds the wheel in place.

Here is the balance wheel in the movement and the cock is the curved, decorated metal plate that extends to the right with the large single screw that anchors it in place.

And here it is removed from the movement. The cock, the balance wheel and hairspring and are all removed as a unit, and great care must be taken to not damage the truly tiny (and delicate) hairspring.

Note the that outer band of the balance wheel itself is actually split at opposite ends. It is by design, allowing subtle expansion and contraction of the metal based on temperature which helps with precision in time regulation.

In normal maintenance of a mechanical watch the hairspring needs to be cleaned, and very carefully so. The whole shebang is dipped in a special cleaner for just a couple seconds and then blow dried.

Here's the master demonstrating.

He's resting the whole mechanism on what's called a balance tack. The screw hole of the cock slips over the tip of the tack (stop giggling!) and holds the balance wheel unit in place so you can inspect/work on it.

Your correspondent remembers thinking "I have never heard of a balance tack. Where the hell am I going to get one of those?" 

Well, in case you, dear reader, might enjoy having one of your own, they are easily purchased from your local watch supplier or Amazon (shocker, I know). 

And here's another thing to point out. Behold our balance wheel flipped over.

See the serial number stamped on the underside of the cock? It matches those stamped on other components of the watch and indicates that the movement parts are all original to this specific watch. In this case the number stamped on components is actually the last 6 digits of the serial number. The first 2 digits ("1 5") likely connote the particular batch/run of that manufacturing. The full serial number is displayed on the main bridge of the movement. 

Examples on other parts from my prior posts on the watch.

Gotta admire the quality of the manufacturing.

I'm going out of sequence but as I was writing this it occurred to me that I should point out something else about the quality of this "inexpensive" watch...

Until the middle of the 20th century most watch dials were made of fired enamel. Enamel watch dials can be very beautiful however it is quite common for dials to have hairline cracks, fractures or even chips in the enamel surface.

Here's a different Waltham 12s 210 model that is on my bench now. That chip near the 5 is particularly bad. I purchased it as a "parts" watch to learn from. It was a dirt cheap buy on eBay, likely because the dial was so damaged.

In other respects that watch is lovely and keeps great time. Maybe I'll just replace the dial. 

Or maybe I won't.

Back to the 12s in the classroom...

The dial from our watch is just about flawless. 

And once it was removed from the movement, immediately evident on the back of the dial was the beautiful bluing effect from the enameling process like that from the (approximately) 165 year-old French black marble Japy Freres clock that I worked on a few years back. 

OK back to the disassembly...

Which I will further describe in another post.