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?

NY wrote:
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?



My suspicion is the escapement is worn so the going train ( the gears
which, in simple terms turn the hands) arent 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.

"Radio Man" wrote in message
...
My suspicion is the escapement is worn so the going train (the gears
which, in simple terms turn the hands) arent 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.

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.

On 20/08/2020 12:43, Chris Hogg wrote:
On Thu, 20 Aug 2020 12:23:02 +0100, "NY" wrote:

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.

Something about the pivot point or pendulum amplitude has changed then.

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.

It should not be too sensitive to absolute level provided that it isn't
obviously cock eyed or rocking on its feet.

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?

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.
https://www.careline.co.uk/wp-conten...5/p040d4h0.jpg
Perhaps you could try something similar: little pieces of solder wire
wrapped around the rod just above the bob, for example.

That is true for a simple pendulum but if the bob isn't very heavy when
compared to the mass of its support then that rule is only approximately
right. Likewise being independent of amplitude is only approximate too.

I have a couple of tiny brass nuts sat on my torsion pendulum to correct
out slight imperfections of its compensation with ambient temperature.
In theory is is fully temperature compensated by design.

Some pendulum clocks are too with a pair of different metals invar for
the longer length and then brass or iron for a short length so that the
pendulum bob position stays fixed as a function of temperature.

--
Regards,
Martin Brown

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

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"NY" wrote in message
...
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?

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

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The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Chris Hogg" wrote in message
...
On Thu, 20 Aug 2020 12:23:02 +0100, "NY" wrote:

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?

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.
https://www.careline.co.uk/wp-conten...5/p040d4h0.jpg
Perhaps you could try something similar: little pieces of solder wire
wrapped around the rod just above the bob, for example.

--

Chris

On Friday, August 21, 2020 at 7:55:42 AM UTC+1, Brian Gaff (Sofa) wrote:
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

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The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!


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.

On 21/08/2020 09:24, Rob Graham wrote:
On Friday, August 21, 2020 at 7:55:42 AM UTC+1, Brian Gaff (Sofa) wrote:

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.

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.

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.

--
Max Demian