[time-nuts] Regulating a pendulum clock

Javier Herrero jherrero at hvsistemas.es
Mon Aug 9 18:19:51 UTC 2010


Not so simple... you should move it around in order to balance the 
gravity force vector :)

Regards,

Javier

El 09/08/2010 20:09, J. Forster escribió:
> 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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>
>
>
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-- 
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Javier Herrero                            EMAIL: jherrero at hvsistemas.com
HV Sistemas S.L.                          PHONE:         +34 949 336 806
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