Adjusting the pendulum of a grandfather/mother/daughter clock so it keeps good time

[NY]

I have a granddaughter clock and I'm having great difficulty adjusting it so it keeps good time. The pendulum bob (a metal disc) sits loosely on a threaded rod which has lugs allowing it to sit on the oscillating part of the clock mechanism. The bob rests on an adjustable nut on the rod, which allows the pendulum to be lengthened or shortened.

It used to lose about 5 minutes a day, but I've progressively wound up the nut 1/2 turn at a time, to shorten the pendulum so it has a shorter period. I'd got it almost right, but then I went backwards: a further shortening made it run *slower*. I wound the nut a full turn shorter which was evidently too far (the clock ran too quickly), but when I backed it off 1/4 turn, it started to run a lot slower than before I originally adjusted it.

Part of the problem is that it is necessary to turn the clock round to get at the back, and then unhook the pendulum from its mount on the mechanism to be able to get at the adjustment screw. I'm wondering whether it doesn't always reseat to the same position and/or slight differences in how the clock sits on the floor are making things non-reproducible.

The floor is modern hardwood tiles laid on a concrete floor that was levelled with self-levelling compound when we had building work last year, so it's not the problem of a sloping floor or a carpet that is thicker near the walls than a few inches into the room.

Any suggestions?

[Chris Hogg]

Time-keeping of the clock in the Elizabeth Tower (aka and wrongly called 'Big Ben') is done by adding or subtracting weights (old pennies etc) to the main pendulum weight. In principle, the period of a pendulum is independent of the mass of the bob, but by adding or subtracting pennies they shift the C of G slightly, altering the effective length of the pendulum.

you could try something similar: little pieces of solder wire wrapped around the rod just above the bob, for example.

[Radio Man]

My suspicion is the escapement is worn so the going train ( the gears which, in simple terms turn the hands) aren?t being released consistently or imparting the impulse to the pendulum consistently.

When the pendulum is grossly too long, the wear is masked. As you correct the length, the wear problem dominates.

[NY]

Ah, right. The clock is due to be examined by a reputable clock repairer in due course, so we'll see what he says. First priority is two other granddaughter clocks (they all belonged to my grandparents) which don't go at all for more than a few minutes which suggests that the pendulum is not being given repeated "kicks" to keep it swinging. The one I was trying to adjust is a lower priority because it runs and keeps fairly good time: having to correct it by a few minutes once a day and to keep it fully wound (or else it stops) is a small price to pay.

[Brian Gaff (Sofa]

The mechanism its self is worn, dirty or needs some tlc? I had a wall clock that did this sort of thing as well. It was fine after cleaning but I moved it on and is its tick was loud and you could not stop the chimes. Brian

[Brian Gaff (Sofa]

It should not be any different to the shortening and lengthening though, my guess is that the clock is not very accurate as it has worn parts dirt or no lubrication, but do be careful with the latter, its quite a specialist subject cleaning and lubricating a clock.

Is it one which is operated by clockwork or the weight driven kind, the latter can be very temperamental. Brian

[Rob Graham]

I don't want to be a nay-sayer to Brian's comment about 'a specialist', but there is plenty of guidance around in books etc., on cleaning a clock mechanism, which is realy incredibly simple. The biggest concern is wear on the bushes which does become a specialist area.

I've sorted two old pendulum clocks without any previous experience with guidance from a book " Practical Clock Repairing" by de Carle, and a number of years later they still operate satisfactorily.

[Max Demian]

You've got to take it all apart, clean it with a solvent, reassemble and lubricate each bearing with a minute amount of oil. Not a straightforward process.