Longer-Term Beat Plot
The first four beat plots looked at the beat variation that occurred during individual rotations of the escape wheel. If one looks at a longer term trend one can see the impact of the wheel driving the escape wheel – as shown in this plot – which is based on the same data set as the previous plot. In this plot, the pattern that is created by the longest tick in each rotation of the escape wheel (the uppermost points in the mass of data) show a trend, increasing and decreasing in a fixed pattern. The duration between the highest of these “longest ticks” are 8 turns of the escape-wheel apart. In that the ratio of turns of the escape wheel to the wheel driving the escape-wheel’s pinion is 8 – it is apparent that there is an aberration in the interaction between the escape-wheel's pinion and the wheel driving it.
It is important to realize that, in a dead-beat escapement, the difference between the tick and the tock is dependent on the amount of over-swing in the escapement. Whilst the duration of the average of the tick and the tock stays nearly constant (the impact of “circular error” would be the cause of variation of the average, but this is very small next to the variations in the tick and the tock), the difference between the tick and the tock increases as the pendulum swing width decreases. And, realizing that the amount of over-swing, and hence the width of the pendulum swing, decreases with decreasing driving force, then the maximum tick duration in this figure can be related to reduced driving force. Or, for this clock, the wheel driving the escape wheel is perhaps slightly off-center – resulting in a periodic increase and decrease in the force applied to the escape wheel, or possibly a bent tooth in the driving wheel, resulting in a decrease in driving force at that point in the wheels rotation.
Plots like the last two show the benefits of learning to import data into a program like Excel - you can do so much more with the data than just look at the plots that are available via the Microset program.