How do we go about adjusting a watch? This series of posts explains dynamic poising, an approach to positional adjustment that is nothing short of a watchmaking marvel.
In this post, we’ll start with the fundamental question: Why do watches have different rates in different positions? We can’t tinker with a watch to have similar rates if we don’t know why they differ.
Our Patient: Hamilton 1954 “Fulton” Wristwatch
For our running example across these posts, we’ll use our current patient: a Hamilton “Fulton” wristwatch with a 17-jewel 747 mechanism. Although made in 1954 and thus over 60 years old, this watch has great potential.
The mainspring was replaced, and the watch was cleaned, oiled, demagnetized, and left running for a day.
Let’s start by looking at what rates this little guy has in the 5 wristwatch positions. I wound up the watch fully and then nudged the regulator to bring it close to zero in the dial up position, and here are the specs. The numbers are the rate (seconds fast or slow per day) and amplitude (in degrees), a concept we’ll delve into later on in the series
The horizontal (lying) positions:
- DU (dial up): -1 (291)
- DD (dial down): +21 (275)
And the vertical (hanging) positions (the amplitude was over 240 degrees in each case):
- PU (pendant up): -11
- PL (left): +14
- PD (down): -27
- PR (right, the 6th position): -68
Evaluating the Results
These numbers are fairly typical for a freshly cleaned vintage watch. Let’s boil them down:
- Across all 6 positions, the average absolute deviation (disregarding slow or fast) is 14.8. On average, each position is around 15 seconds away from 0.
- The DU and DD positions differed by 22 seconds—that’s not good. Their average rate was +10.
- The largest difference between the 4 vertical positions was huge—82 seconds (PL and PR).
- The difference between the average horizontal position (+10) and the average vertical position (-23) was pretty big: 33 seconds.
Overall, the Fulton’s rates across positions are pretty bad, but this is exactly the sort of watch you see listed for sale as “serviced!” and “keeps great time!” on eBay. It is essentially adjusted to 1 position—dial up, where it does keep excellent time—but obviously we wouldn’t be happy with these timing numbers or see this watch as ready for daily wear.
The Basic Task of Dynamic Poising
Looking at this example helps us unpack the basic task of adjusting for positions. We are trying to accomplish 3 things:
- Align the horizontal positions. We want the watch to have the same rate dial up and dial down.
- Align the vertical positions with each other. We want the watch to have the same rate in all 4 hanging positions.
- Align the average horizontal rate with the average vertical rate. We want the lying and hanging positions to be close.
So these are the 3 tasks of dynamic poising. We accomplish them in 2 steps:
- First, we align the DU and DD rates.
- Second, we align the 4 vertical positions in a way that simultaneously aligns the average horizontal and vertical rates.
Confusing? Don’t worry about it. That’s why there are so many old books on watch adjusting. But keep reading—it will make more sense as we work through Fulton, our valiant patient.