[time-nuts] Regulating a pendulum clock (Jim Palfreyman)

[Steve Rooke]

On 08/08/2010, mike cook <mike.cook at orange.fr> wrote:
> Check out Bryan Mumfords page.
> http://www.bmumford.com/clocks/em2/index.html

I did not want to kick the pendulum with a pulse each swing as the
drive would be part and parcel of the existing clock mechanism. What I
was interested in was Don Mimlitch's description of how the Riefler
Pendulum and Warren Telechron Master Clocks work. The control of
constant current to the electromagnet under the pendulum seems quite
similar to an EFC and could perhaps be used in a PLL to sync with a
reference source, as Jim was originally proposing.

Of course, retrofitting a conventional clock like this would require
the attachment of a magnet to the pendulum, necessitating reducing the
weight of the pendulum to account for it, installing an electromagnet
under the pendulum and arranging for each swing of the pendulum to
produce some form of pulse signal. Of course, the timing in pulses per
second of the original clock would have to be determined and the
frequency standard divided down to match this rate before both signals
are fed to a comparator and LPF to provide the 'EFC' voltage to
control the electromagnetic current.

Steve

> Le 08/08/2010 11:14, Steve Rooke a écrit :
>> I was rather more thinking of the setup that Don was suggesting as not
>> many domestic clocks have a seconds pendulum and it would otherwise
>> take dividing down a referenced oscillator to the correct frequency.
>>
>> Cheers,
>> Steve
>>
>> On 08/08/2010, Neville Michie<namichie at gmail.com>  wrote:
>>
>>> Not many clocks are set up with the gear to modulate the rate,
>>> but they are all still sensitive to injection locking.
>>> A tiny rare earth magnet on the pendulum (say 1/2 way down the
>>> pendulum rod)
>>> and a coil fed with a stretched (say 250ms long) PPS or for a seconds
>>> pendulum
>>> PP2S pulse will pull the pendulum into phaselock with a surprisingly
>>> small amount of power.
>>> In fact if you turn off the drive it would keep the pendulum swinging.
>>> Cheers, Neville Michie
>>>
>>> On 08/08/2010, at 6:00 PM, Steve Rooke wrote:
>>>
>>>
>>>> This is very interesting and I wonder if the capabilities of this
>>>> system being applied to any clock pendulum. If this sort of control
>>>> any pendulum, then I wonder if it's possible to sync it to some
>>>> standard.
>>>>
>>>> Steve
>>>>
>>>> On 08/08/2010, Don Mimlitch<donmeis at yahoo.com>  wrote:
>>>>
>>>>> Jim Said:
>>>>>
>>>>>> It also has a coil mounted near the pendulum and a fixed magnet
>>>>>> on the
>>>>>> pendulum bar and this coil connects to a box down below with a meter
>>>>>> and a knob. They are labeled in sec/day. The electronics in the box
>>>>>> are not clear (being quite old) but by measuring the current in the
>>>>>> coil it quite simply increases the current one way to slow the clock
>>>>>> and the other way to speed it up. (I'll admit the physics of this
>>>>>> doesn't make sense to me - but it works!)
>>>>>>
>>>>> I have a Warren Telechron Master Clock used in Power Stations in
>>>>> the 20's to
>>>>> regulate the 60 Cycle so that household clocks using synchronous
>>>>> motors
>>>>> would be accurate to seconds a day.
>>>>>
>>>>> This clock has a similar permanent magnet at the end of the
>>>>> Pendulum and
>>>>> a battery connected to a potentiometer to adjust the current flow
>>>>> positive
>>>>> or negative in an electro-magnet below the pendulum..
>>>>> If the bottom of the magnet in the pendulum is "north" and the
>>>>> current in
>>>>> the electromagnet is flowing such that its top face is North, then
>>>>> this will
>>>>> repel the pendulum causing its swing to be wider and contrary to
>>>>> common
>>>>> knowledge the swing of a fixed length pendulum is not constant
>>>>> regardless of
>>>>> the swing. (Huygens discovered this in 1670 an found by forcing
>>>>> the arc of
>>>>> the swing to be cycloid instead of circular he could produce uniform
>>>>> oscillation) Thus if the arc is longer the swing takes more time
>>>>> and the
>>>>> clock runs slower.
>>>>> If the current flows in the opposite direction and the two magnets
>>>>> attract
>>>>> then the arc is shortened and the clock runs faster. Of course my
>>>>> master
>>>>> clock isn't as accurate as a Riefler pendulum clock. Also the
>>>>> magnet in my
>>>>> clock has lost it's magnetism over time and I can't use this
>>>>> regulation.
>>>>>
>>>>> So the goal of your adaptation is to have precision control of the
>>>>> current
>>>>> flow in the positive or negative direction. Others on the list are
>>>>> better
>>>>> then me at describing how you might achieve this.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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>>>>>
>>>>
>>>> --
>>>> Steve Rooke - ZL3TUV&  G8KVD
>>>> The only reason for time is so that everything doesn't happen at once.
>>>> - Einstein
>>>>
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-- 
Steve Rooke - ZL3TUV & G8KVD
The only reason for time is so that everything doesn't happen at once.
- Einstein