Introduction

I design and make ‘contemporary’ pendulum clocks. My aim is to simplify and integrate both mechanism and aesthetic aspects to maximize the visual effect. Accurate time-keeping is obviously important. In this respect, inspiration comes from innovators of the twentieth century including Riefler, Hope-Jone, Shortt, Fedchenko, Woodward, Arnfield, Matthys and Stephen. Aesthetically, I admire the work of Forrest, Burnett, Hunkin, Plant and Kazes. I am particularly interested in the use of new materials, modern thoughts on pendulum and escapement design, and the use of mathematical optimization using MathCad Software.

Table Regulator B1

Designer: Roger Bunce

Makers: Engineering Staff, Wolfson Research Laboratories, University of Birmingham, May 1983.

Description: Mains operated table regulator combining pendulum and microprocessor technology

Case: Clear anodised aluminium and brown tinted glass.

Dial: Black anodised aluminium. Time indication - red LED’s.

Escapement: Electromagnetic gravity escapement with optical feedback. Impulse is provided by a small permanent magnet falling onto a bronze impulse arm. The clock must never be oiled.

Pendulum: Half seconds temperature compensated pendulum with invar rod and stainless steel bob. Secondary compensation is a bronze tube within the bob. Total swing is maintained accurately at two degrees.

Regulation: Weight tray

Timekeeping: About a second per week.

In Retrospect: It was appropriate, at the time, that the Regulator was an interdisciplinary effort involving all the Engineering Staff. It was for this reason that a hybrid design was chosen. However, the problem with this approach is that electronics can be unreliable and specialist components can quickly become obsolete. In addition, such systems are very difficult to repair without full electronic documentation and without the original computer system used to program the microprocessor. For this reason, my next clock - Wall Regulator B2, uses Hipps Toggle – not ‘High-Tec’ but very reliable and easy to repair.

Wall Regulator B2

Designer/maker: Roger Bunce, June 2006.

Description: Wall-mounted regulator with illuminated dial and mechanism.

Dial: Made from Perspex with a mains operated 9W lamp which illuminates both dial and movement. The geometry of the dial was achieved by masking and spraying using automotive acrylic paint on the reverse side.

Time indication: The minute and hour hand follow the normal regulator layout but is achieved using an unusual integrated hour hand and motion work. This was thought to be novel but was later found to be described by Moons & Van Hoof, Dutch Patent 8602561, 1986. The ratchet wheel indicates quarter minutes.

Escapement: Hipps Toggle with harden steel Vee and trigger, modeled using MathCad. The Vee is the only part of the clock which is lubricated (Moebius 8040). I intend to change the Vee material to sapphire, ruby or tungsten carbide.

Contacts: silver with silicon diode spark suppression. Operating voltage is 3V from two 'D' Type Duracell batteries. The batteries last for a year.

Pendulum: Three-quarter seconds, temperature compensated, pendulum with invar rod and stainless steel bob. Secondary compensation is stainless steel integral within the bob. The Pendulum was modelled using MathCad. Total swing is about 5.5 degrees. The regulating nut is calibrated - one notch makes a difference of about one second per day. The nut is fitted with a locking device. The weight tray is for finer adjustment and there is a calibration chart in the base of the clock.

Movement materials: The plates are aluminium alloy (HE30), bead blasted and clear anodised. The contact posts are brass, bead blasted and satin chromium plated. The ratchet wheel and worm and wheel are made from white polyacetal (Delrin), and are not lubricated. The bushes are Polyetheretherketon (PEEK) Bearing Grade and, again, are not lubricated. This material is not easy to machine - it 'rags' and blunts HS tools quickly. Steel parts (not requiring hardening) are made from free cutting stainless steel (303). All screws are stainless steel and have socket heads (Avoiding scratched plates and chewed-up screw slots!).

Case: 1090mm tall, made from American cherry, Russian birch, Canadian Yellow Pine and toughened glass. The wood is finished using Osmo TopOil. The case is in the form of two 'L' shaped sections. The left hand section forms the hinged door. This geometry allows good access and provides an undisturbed view of the mechanism.

Timekeeping: About one second per week.

On Reflection: Hipps Toggle is, to my mind, incredibly elegant. However, this largely traditional implementation is not without its faults. The main problems are: The offset trigger causes axial wobble of the pendulum. The Vee and magnet distances from the pendulum pivot vary with temperature. Battery voltage effects timekeeping and residual magnetism is another variable. However, the system is very simple, reliable, and quiet and, while the timekeeping is not up to 'observatory precision', a second per week is adequate for most domestic purposes.