Adjust Moon Phase and Beat on Regulators and Grandfather Clocks

In this article, you will learn how to correctly set the moon phase and beat error on regulators and grandfather clocks. As an example, we show the Hermle 01131-031171 grandfather clock.

What exactly is a moon phase?

In common usage, a distinction is made between new moon, waxing moon, full moon, and waning moon. New moon (empty phase), full moon (full phase), and the two half-moons are referred to as the main phases. At half moon, the half phase (dichotomy), half (50 %) of the sunlit lunar surface is visible. The waxing moon is seen in the evening sky during the first quarter of the cycle or in the first half of the night, while the waning moon is seen during the last quarter in the second half of the night or in the morning sky. Before the half phase of the first quarter and after the half phase of the last quarter, the Earth’s satellite appears as a crescent moon. When it first becomes visible in the evening sky after new moon as a thin crescent, it is called the new light; at its last visibility in the morning sky before new moon, the old light.

How do you correctly set the moon phase on a wall clock?

1. Press the button until the full moon appears in the display.
2. Then find out on which day the last full moon was.
3. Count the past days since the last full moon and press the button that many times.

What exactly is beat error on a wall clock? In horology, beat error refers to the symmetry of the rate, i.e. the relative position of mechanical timekeeping regulators and the associated escapement parts. The escapement’s task is to prevent the gear train from running free and to supply the oscillating system with energy to maintain the oscillation. The escapement creates a systematic, amplitude-dependent rate error, in most escapements a loss of time. The anchor escapements commonly used today transfer the energy lost through friction to the oscillating system in the form of an impulse near the rest position. The disturbance component before and after the rest position has a major influence on the clock’s rate error, which can be quantified by Airy’s relations. For accurate and also stable running of the clock, it is essential that the escapement action is symmetrical during both half-oscillations of the timekeeping regulator (pendulum or balance wheel).

How do you set the beat error on a wall clock?

On a wall clock, the beat error can be adjusted and set at the movement. This is done during servicing. But if the clock hangs crooked, the beat error changes as well. You can hear it clearly when it makes tiick-tack or tick-taack instead of tick-tock, and if you overdo it, it stops. The beat error changed by the tilt also affects the rate behavior (fast/slow), in addition to the pendulum length adjustment.

• On high-quality pendulum clocks, the rate symmetry can be adjusted at the beat adjuster of the pallet fork; on simple pendulum clocks, this is done by carefully bending the pallet fork.
• On small clocks, there is either an adjustable beat-holder on the balance cock, or the collet must be turned on the balance staff. The latter is particularly common in older pocket watches.
• On clocks where the pallet staff is permanently connected to the pendulum leader - whether riveted or soldered - the pendulum leader must be bent.
• Please note that on high-quality clocks, the pendulum leader must be held firmly with 2 fingers, otherwise there is a risk that the thin pallet staff pivots will break.
• If the pendulum leader and pallet staff are not firmly connected to each other, but can be twisted relative to each other, then you must note the following when correcting it:
  1. Tilt or lean the clock case far enough to the left or right until the ticking is completely even.
  2. Carefully move the pendulum leader in the direction of the tilt until the pallet rests in the tooth space of the escape wheel and a slight resistance is felt.
  3. Push the pendulum leader slightly beyond the resistance. If the freedom of movement of the pendulum leader is restricted, you must lock the pallet with your free hand and hang the clock upright again.
  4. Now listen to the ticking again.
  5. If the ticking is still not even, please repeat the adjustment process - if necessary, also in the opposite direction.
• High-quality clocks and precision pendulum clocks have a specially designed pendulum leader. On such clocks, there is an adjustment screw or a knurled wheel on the leader for fine adjustment. With this regulating device, you can easily and conveniently set an even tick-tock.