[time-nuts] Regulating a pendulum clock
bill at iaxs.net
Mon Aug 9 20:36:06 UTC 2010
Ahhh, this is more like it! Large gears and thick ropes moving
heavy weights up and down. :)
Of course, you wouldn't want anything digital doing this. Just
a large pendulum clock driving a maze of gears that calculate
solar and lunar positions.
From: J. L. Trantham, M. D.
Sent: Monday, August 09, 2010 3:10 PM
Personally, I would get out of the way. : )
From: Ian Sheffield
Sent: Monday, August 09, 2010 1:17 PM
What happens when the rope breaks?
From: J. Forster
Sent: 09 August 2010 19:10
You could put a large mass of concrete or somehing above the clock and
crank it up and down, to balance out the computed gravity changes.
> Unfortunately Gravity is not constant. Pendulum clocks show cyclic errors
> due to the influences of the Moon's and Sun's Gravitational fields. I
> forget the amounts but it is in the region of parts in 10 to the 7, which
> is easily measurable.
> This limits the compensations one can put into a pendulum clock.
> -----Original Message-----
> From: mike cook
> Sent: 09 August 2010 18:21
> On 09/08/2010 18:46, Bob Holmstrom has written:
>> Food for thought.
>> I find it interesting that no one has suggested alternatives to
>> improving the performance of a pendulum clock other than controlling
>> it with a higher performance clock. If the goal is a better clock why
>> not attempt to understand the source of the errors and work on methods
>> to control or compensate for them? Teddy Hall has been taken to task
>> for using a quartz controlled oscillator to measure the amplitude of a
>> pendulum in the control loop of his Littlemore clock.
>> Tom Van Baak has developed techniques for analyzing the performance
>> and hence potential error sources of pendulum clocks - perhaps he will
>> share some of his work here.
>> Horological history is full of many attempts at solutions to the
>> problem, but it would seem that the creativity of this group might
>> generate some new ideas that are more in the spirit of better
>> timekeeping than attaching the pendulum to a better oscillator.
>> How about a wireless controlled device attached to the pendulum that
>> changes its position based on error sensor readings, not time errors,
>> but instead, temperature, barometric pressure, gravity, etc. that
>> would maintain a more constant pendulum period?
> Yup. We have temperature and pressure ICs available , I think that
> gravity is pretty constant if the clock isn't being moved about.
> Humididty might also need logging aswell. So it should be easy enough to
> predict the pendulums response to changes given a reasonable time of
> That said, clocks have always been adjusted against better
> references.. IIRC Harrison (and probably others) was using star transits
> to regulate his long case clocks.
>> Bob Holmström
>> Horological Science Newsletter
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