Fig. 1 The New Arnfield Clock
The Arnfield clock (Fig. 1) has been completely rebuilt. Although the principle of operation is the same, the design has been radically altered. The Arnfield has a unique escapement whose aim is to interfere with the natural action of the pendulum as little as possible. An impulse arm influenced only by gravity keeps the pendulum oscillating, but the unlocking of the escapement wheel is independent of the pendulum action and is carried out by the impulse arm itself after it has been detached from the pendulum. The Huygens power supply has been replaced with an epicyclic planetary rewind mechanism where the weight of the small 6 volt motor is itself the driving force and the battery life is sufficient to drive the clock for months unattended. The motor is controlled by a relay operating between limit switches although a gravity mercury switch can also be used.
The escapement (Fig. 2) has been greatly altered to produce a decreased pendulum amplitude. A prominent seconds hand is positioned above the main clock face. The pendulum is now positioned behind the clock plates and its length can be easily altered to adjust timekeeping. The mechanism is now more compact with a smaller clock case so that the clock can be displayed on a table or shelf.
Fig. 2 The escapement from the New Arnfield Clock
The mechanism was invented in 1987, and has attracted a great deal of attention. It has a visually attractive action, and is reliable and keeps very good time.
The ModelPlan is available from MW Mail order