Congreve Clock revived
Timm Delfs
Two students of the Grenchen watchmakers’ school, the “Zeitzentrum”, have chosen to build a Congreve clock to finish their studies. Lorenz Brandel and Joé Wagner had been pondering for some time what to choose as a theme for their diploma until they came across the image of a clock that was equipped with a strange kind of regulator organ: instead of a pendulum or a balance wheel, it featured a slightly inclined rectangular rack on which a small steel ball ran on a zig-zag track. They found out that whenever the ball reached the end of its helter-skelter track, it hit a thin rod which in turn triggered a cascade of events in the clockwork: it released the escapement wheel that, having only two teeth, made half a revolution. A lever attached to it at the same time lifted the rack, making the ball reverse its itinerary lasting 30 seconds each time.
The two were mesmerised at what they saw and wanted to see it in action. Realising that there was no such clock far or near, this meant they had to build one themselves.
The Congreve clock takes its name from its inventor Sir William Congreve, born 1772 in Kent. It is really a by-product of a genius who had dedicated his life to the development and constant improvement of rockets for military use. He is also the inventor of a printing method named after him. He died 1828 in Toulouse.
Initially Lorenz Brandel and Joé Wagner intended to construct the entire mechanism themselves, having as a reference only the picture they had found. Soon they had to realise, though, that things weren’t that easy. They had to ask their teacher Roland Wyss for help. He gave them a book by John Wilding that contained a detailed guide to constructing a Congreve clock. Alas, all the measures were in inches, though. The two decided to only retain the number of teeth of all the gear trains and define the rest of the proportions themselves.
The result of roughly 750 hours of work is quite spectacular and well worth the maximum mark they were given by the experts of the school. The clock was executed combining modern materials like anodised aluminium and industrial ball bearings with traditional materials like brass and gold. The finished clock presents itself in two main colours, gold and black. “We decided for a distinctive colour code using black for all the vertical elements, wheels excepted, and gold for everything horizontal”, explains Lorenz Brandel. The clock is divided into two levels, the lower level housing the steel ball mechanism and, suspended by four black columns, the upper part with the actual movement and dials. There are three dials in a horizontal line displaying (from left to right) hours, minutes and half minutes. The hand of the latter, being mounted directly on the axis of the escape wheel can only perform jumps of 30 seconds, this being the frequency of the ball’s zig zag itinerary across the inclined rack.
The Congreve clock is by virtue of its construction no precision clock. Too many factors can influence the speed of the ball on its way down. In order to avoid any other disturbances the two watchmakers included a fusée pulled by a black steel cable in order to guarantee constant force on the escapement, knowing full well that the force saved in the barrel declines as the spring slowly unwinds. Except for the silvered dials all circular elements are gilded. The combination of these colours lends this exotic timepiece its noble character. ■
