[time-nuts] Regulating a pendulum clock

J. Forster jfor at quik.com
Mon Aug 9 22:24:06 UTC 2010

Nah! No ropes or gears. Just a SS tank on steel stilts and a big mercury
reservoir and a pump.

And it might not have to hold tons. Think of a hollow SS donut with the
pendulum in the clear space.




> 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.
> Bill Hawkins
> -----Original Message-----
> From: J. L. Trantham, M. D.
> Sent: Monday, August 09, 2010 3:10 PM
> Personally, I would get out of the way.  : )
> Joe
> -----Original Message-----
> From: Ian Sheffield
> Sent: Monday, August 09, 2010 1:17 PM
> What happens when the rope breaks?
> -----Original Message-----
> 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.
> :)
> -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: 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
>> 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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