[time-nuts] Regulating a pendulum clock

Ian Sheffield ian.sheffield1 at tesco.net
Mon Aug 9 18:17:23 UTC 2010


What happens when the rope breaks?

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of J. Forster
Sent: 09 August 2010 19:10
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Regulating a pendulum clock

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.

:)

-John

==============


> 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: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of mike cook
> Sent: 09 August 2010 18:21
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Regulating a pendulum clock
>
>
>
> Le 09/08/2010 18:46, Bob Holmstrom a écrit :
>>
>> 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
> observation.
>   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
>> Editor
>> Horological Science Newsletter
>> www.hsn161.com
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>
>
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