[time-nuts] GPS disciplined mechanical clocks

Neville Michie namichie at gmail.com
Thu Mar 5 05:49:39 UTC 2009

In the evolution of timekeepers the SHORTT CLOCK was one of the great  

see           http://www.electric-clocks.nl/clocks/en/page10.htm

This clock used a pendulum running free to synchronise another  
pendulum that did all the housekeeping work.
The work pendulum was adjusted to be a little slow and a thin leaf  
spring was picked up by a relay if the phase was too
slow and added a slight gaining rate until the phase was restored.
A little like switching a tiny capacitor in and out connected to an TCXO
to keep it disciplined.
These clock kept very good time.
Cheers, Neville Michie

On 05/03/2009, at 3:11 PM, Eric Williams wrote:

> Bryan Mumford (bmumford.com) did a lot of work developing pendulum  
> clocks
> that were driven by a Fedchenko electromagnetic drive.  The drive  
> circuit
> would both put energy into the pendulum and use the pulse to drive an
> electric clock face to display the time.  He never got to the point of
> disciplining the clock, but he did note that you could make fine  
> adjustments
> in the period by varying the drive current which changed the  
> amplitude of
> the pendulum swing and changed the period.  (Larger swings ran  
> slower, as I
> recall.)  You could theoretically discipline such a clock by  
> varying the
> current to lock the pendulum to a GPS source.  It wouldn't really be
> mechanical, more of a hybrid, but I don't know how you'd discipline a
> mechanical clock with a system that had to drive in parallel with  
> the escape
> mechanism, the two would fight each other.
> On Wed, Mar 4, 2009 at 3:52 AM, Steve Rooke <sar10538 at gmail.com>  
> wrote:
>> Has anyone looked at locking an old mechanical clock to precise time?
>> What I'm thinking of is something like an old cuckoo clock. The rule
>> is that the clock remains basically standard and is only steered by
>> the external source, say, by a magnetic pulse to the pendulum, IE. no
>> physical connection. Obviously the correct period of the pulse would
>> have to fit the timing of the pendulum. OK, it seems pointless as you
>> can't read time with any real accuracy on something like a cuckoo
>> clock but I'm sure there is the likelihood of something like this
>> being done by someone like us.
>> 73,
>> Steve
>> --
>> Steve Rooke - ZL3TUV & G8KVD & JAKDTTNW
>> Omnium finis imminet
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