[time-nuts] Regulating a pendulum clock

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Aug 9 20:21:57 UTC 2010


Advisable given the required mass will probably be in the 10-100 ton range.

Bruce

J. L. Trantham, M. D. wrote:
> Personally, I would get out of the way.  : )
>
> Joe
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of Ian Sheffield
> Sent: Monday, August 09, 2010 1:17 PM
> To: jfor at quik.com; 'Discussion of precise time and frequency measurement'
> Subject: Re: [time-nuts] Regulating a pendulum clock
>
> 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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>
>
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