Horological Meandering

Some horological history, a visit to the Zytglogge in Bern

Dec 28, 2017,15:40 PM

Although we can hardly believe it today, having a clock was once so rare that it was a prestige object for a town to have a tower clock. And all the clocks were “repeaters” so that everyone in the town could hear the time struck on the bells to call then to work or to prayer.

One of these prestige objects is the Zytglogge in Bern. This clock has been ringing for the citizens of Bern since about 1405. The tower the clock is in was origanally built around 1218 as a fortified gate in the wall around the town. As the town grew it was no longer at the peripherie but in the middle of the town. In the years before the installation of the clock it was used as a prison.

In 1405 a major catastrophy happened in Bern. There was a fire that burned about half the town down to the ground. That fire caused many changes in Bern, for example the buildings were from then on made mainly of sandstone and not wood. Also other materials such as tiles were used as roofing to replace the highly inflammble thatching used up 'til them.
The bells that hang in the cupula at the top of the structure are cast bronze. The larger hour bell is from 1405, the smaller quarter hour bell was cast in 1887 to replace a bell from 1486 that had cracked. The hour bell is struck by a life size Jaquemart figure that is activated by the clock movment (in the first picture).

The first mention of a clock in this building was at the installation of the hour bell in 1405. The first mention of a clock dial from 1443, an astronomical dial. The present astronomical dial is from either 1405 or 1467-83 when the building was expanded. The eastern clock face corresponds to the renovation from 1770 while the western clock face is part of a wall fresco from 1929 by Victor Surbek.

The glockenspiel is run by the clock movement once an hour. The rooster crows, the jester plays the small bells, a group of bears promenade around the base and when it is time for the Jaquemart to strike the bell Chronos sitting in the middle turns his hour glass.

After this lengthy intro let's go up the narrow winding stairs to see the mechanics.

The size of the movment is impressing and we understand why it was forged in a fireplace in the room.

The present clock movement was made in 1530 by the clockmaker Kasper Brunner. The movement originally had a foliot as it was made before the invention of the pendulum. The movement was converted to a pendulum by the French clockmaker Pierre Angely around 1686. The pendulum bob is a cannonball.

Here we see the verge escapement at the top of the movement.

There are several interresting things to notice. For example all the teeth of the larger gears can be replaced individually when they wear out.

The clock has 5 barrels to supply the energy for the clock itself, the bell striking and the glockenspiel.

The glockespiel mechanism and the bellows for the roosters crowing.

The pendulum fully swung to one side.

The bell ringing mechanism

Notice also how the bearings for the axles are made, the weight of the axle being taken by a disk below it. This a first step to the disk bearings that Harrison used on some of his clocks.

Here we see the driving weights.

The astronomial dial and the glockenspiel are at the level of the movement. Here we see the driving axles for that dial that go through the wall of the building. Other axles go up to the next story of the building to the big dials.