The Bijou with the silk ribbon

Our clockmakers are among the best in their field. With this unusual regulator, however, even they had to call in a specialist.

Every clock brand has a quality feature that makes it distinctive, unique. It might be a special function or a recognisable design feature. For the clock manufacturer Wilde Brothers of Villingen in southern Germany, which was founded in 1872 and liquidated in 1916, their unique selling proposition consisted of a calendar module that displayed the day, date and month in a window under the dial of their wall regulators.

However, this sort of feature can become a boomerang if it is not technically mature and constantly causes problems. Which was the case with the invention patented by Constantin and Leopold Wilde. For collectors and fans of old clocks, clocks of this kind are still a delight: they are not only technically interesting, but also extremely rare – and therefore sought-after.

Just such a clock has found its way into the Beyer clock and watch collection thanks to a donation from a Beyer customer. However, before it can be exhibited, the showpiece needs to be cleaned, restored and put into working order. “I had never seen a calendar module like this before,” says Tobias Burtscher, head of Beyer’s clock atelier. “Fortunately, René Rietmann, whose clock workshop in Zollikon we took over last year, put me in touch with someone who specialises in this product.”

A case for two: Rudolf Bucheli (right) explains the quirks of the rarity to Tobias Burtscher.

Now we are standing in this Beyer workshop in Zollikon, and Burtscher lets us take a look at the mechanism hidden behind the door of the Renaissance-style wooden case. The clockmaker has not yet touched the inside because he waiting for the specialist before starting on the dismantling. The doorbell rings: Rudolf Bucheli is here. He has brought along a folder with documents about the clock as well as special tools, including a device he built himself for fixing the calendar module, which is larger and heavier than the actual clock movement.

Rudolf Bucheli takes a quick look at the clock and immediately sets to work. Together with Tobias Burtscher, he takes the movement and module apart. Burtscher says with a grin: “We clockmakers often wish we had more than two hands: with four you’re finished in no time.” Bucheli points to a roll on which a silk ribbon with numbers is wound: “That’s what makes this clock so special – but it’s also the Achilles heel and responsible for the fact that this system was never going to have a future.”

While the days of the week and the month names are printed on multi-sided rollers that gradually rotate, the numbers for the date are imprinted on the silk ribbon, which is unwound from one reel and wound onto a second one, a bit like a reel-to-reel tape recorder. “With this invention, the Wilde brothers created more problems for themselves than they solved,” says Bucheli. “The biggest being the material itself: silk is a natural product that reacts sensitively to light and mechanical stress. Its properties change over time and are unpredictable.”

That this is the case becomes clear when the mechanism is dismantled step by step: the silk ribbon is already torn at the point where it is fed through a slit into the drum that winds it up. If the clock is to display the date again, it will need a replacement. The ribbon looks beautiful as it shimmers in the spring sunshine on the worktable. But why aren’t the numbers evenly spaced?

You may remember: in 35mm cameras, a sprocket roller engages with the evenly spaced perforations along the edges of the film, ensuring that the film is always wound on by slightly more than the width of one frame after each exposure. Not so with the Wilde brothers’ calendar clock: in this case, it is the winding spool that rotates further each time the date changes and thus carries the silk ribbon forwards. As its diameter increases incrementally by the thickness of the silk ribbon wound around it, it advances a little more ribbon each day. So if the numbers are to be centred in the date window, the spacing has to increase. “I created multiple Excel files to determine the correct spacing of the numbers for the many different tape materials I tried out,” sighs Bucheli. “And just when I thought I had found a formula, it turned out in practice that I hadn’t taken some factor or other into account.”



It appears that the Wilde company also struggled with this problem and fitted its calendar mechanism with a roller that had short metal pins on the edge. The idea was that these pins would penetrate the silk fabric, so that it would be transported more smoothly. However, this solution gave rise to new problems: over the years, the perforations in the silk ribbon became elongated, tore entirely or got snagged on the pins when rewinding at the end of the month. In short, the silk ribbon developed runs.

But Tobias Burtscher and Rudolf Bucheli are not fazed by such challenges. They begin by cleaning the components in an ultrasonic bath, then check each individual part to ensure that it is functioning properly. Finally, they assemble the calendar mechanism.

Rare calendar module in a decorative Renaissance design: the regulator was donated to the Clock and Watch Museum.

Bucheli has developed his own replacement for the damaged silk ribbon. After years of experimenting, he has found a material that has none of the disadvantages of silk ribbon while retaining the same flexibility – and can be machine-printed.

By the time you read this, the regulator will once again be ticking away in its ornate wooden case and may already be on display in the Beyer Clock and Watch Museum. However, you are hardly likely to ever witness the moment when the calendar is activated and the ribbon with the date moves: because it always takes place at midnight.

The Beyer watch atelier is the largest workshop of any watch retailer in Zurich.
Beyer employs ten watchmakers and two apprentice watchmakers above the shop at Bahnhofstrasse 31 and in the clock atelier in Zollikon.

BEYER Watch-Atelier

What is a regulator?

The regulator originally referred to an extremely accurate, case-mounted pendulum clock, that served as a time reference by which less accurate timepieces, such as pocket watches, could be set. Regulators were used in clockmakers’ workshops, but also as master clocks in public buildings. As they often had a special dial with large minutes, small hours and small seconds, this layout was given the name regulator dial. Nowadays, the term regulator is often used for other wall clocks with a pendulum and a case.

Beyer Chronometrie