About two years ago I took over responsibility for trying to make sure that All Saints’ Church clock keeps good time.
The clock is through the door next to the organ which leads to a spiral staircase going up the tower. The level with the bell ropes used for ringing the bells is part way up the spiral staircase, and the clock is one floor above this, up a ladder. The bells are even higher up, at the top of the spiral staircase, which becomes even narrower and steeper.
There are two cabinets for the clock: one contains the clock itself and the hour chime mechanism, and the other is for the quarter hour chime. A rotating shaft is connected to the clock hands, and the chime mechanisms are activated by cables. There are more cables leading up from the chime mechanisms to make the bells ring.
The clock mechanism has recently been cleaned. Over the years it had become dirty, and this was made worse when the bells were refurbished a while ago, with dirt falling down from above. Before the engineer came to do the cleaning, I discovered two birds’ nests, one on top of each cabinet. These were probably made by pigeons, and one still contained an egg.
The clock can be adjusted using a large nut on the bottom of the clock’s pendulum bob. This can be screwed up or down to make the pendulum shorter or longer, making the clock run faster or slower. There are two disadvantages to this: changes are fairly coarse and the clock has to be stopped to make the adjustment.
A much better method is to add or remove weights from on top of the pendulum bob, which raises or lowers the centre of gravity of the bob, making the pendulum shorter or longer. There is a cradle on top of the bob for this, and I change the weight using nuts and washers. Altering the weight by only a few grams makes a noticeable difference to the timekeeping over a number of days. This is the way Big Ben’s clock is adjusted, by changing the number of old penny coins on top of the pendulum bob.
Theoretically environmental factors such as temperature, air pressure and humidity should affect the timekeeping of the clock. In reality the clock is very temperamental. It can keep good time for a long period and then suddenly start changing by more than a second a day. So, I may be able to leave the clock for several weeks, or need to go up the tower after only a few days to make an adjustment.
Mike Mount
June 2021
| < Prev | Next > |
|---|