On Tuesday this week, Robin Thatcher, Knole’s Horological Conservator, visited to look at two of the clocks in the collection at Knole (we have five in total). The French Ormolu clock in the Ballroom had begun to lose time quite badly. When we wound the clock each week we corrected the time and turned the regulator to keep it correct, however as the week went on the clock was loosing time again. As we had concerns about the Long Case Clock at the top of the lead stairs too, we decided it was best to get Robin in for clock check up.
Robin looked at the Ormolu clock first. He took the screws out of the dial and carefully removed the movement from its case. It soon became clear that the pendulum suspension, a length of silk thread, had become frayed and would need replacing. Once Robin had replaced the thread and re-attached the pendulum he needed to regulate the clock.
In doing this Robin found that it only took half a turn of the regulating key from maximum gain to maximum lose, before the brass block on the pendulum came out of the crutch. This means that if the key should be turned too far anti-clockwise (so the clock will gain time) then the pendulum drops out of the crutch and could get stuck and further regulation of the clock would not work. To see if the pendulum had become stuck we could only see this by accessing the back of the clock, which is not easy as it is very heavy, and takes at least two people to move it round.
Now we know exactly how little we need to turn the regulator key when we need too, this problem can be avoided in the future. Robin finally oiled the movement before replacing it back in the case and re-fixing the screws.
With the Ormolu clock successfully conserved we moved on to the Long Case Clock. We had found when winding the strike felt rough, and almost crunched as it was wound. Luckily it was a simple problem to fix. Robin traced the issue to the pulley which was dry of oil. Both the pulley and the movement were then oiled, making the winding smooth once more.
Hopefully all five clocks will continue to keep time well until the end of the open season, when they will be allowed to wind down and rest for the winter. The cases will be carefully cleaned and then covered with a Tyvek hat made to fit each individual clock, to protect the case and movement from dust.