[time-nuts] Quartz assisted pendulum clock.

Dr. David Kirkby david.kirkby at onetel.net
Thu Jan 5 20:16:05 EST 2006

jayh6 at verizon.net wrote:
> Arghhh the purist in my recoils at 'modernizing' an antique French timepiece <grin>

I can see that. Although there are no permanent modifications required. 
Just a magnet attached to a pendulum (screw onto thread on pendulum, 
which is threaded) and the rest is electromagnetically coupled.

The problem is that the accuracy of the clock is insufficient for things 
like catching a train. So one tends to need another clock in the lounge, 
which looks horrid by comparison, but is at least accurate.

Long case clocks are a lot more accurate of course.

> There would probably be some benefit to making the pendulum (or balance) consistently a bit slower than the quartz standard so that the pull is always in the same direction to avoid hunting (it's interesting that many biological clocks work this way, without diurnal cues, they run long (25 hr or so) so that the stabilizing influence is always in the same direction.

I think that the energy put into the correction must be higher in this 
case, which is not an issue if you runs from a mains PSU, but is an 
issue if its battery powered.

Also, if it is mains powered, you can avoid a battery backup by not 
requiring a constant correction. A small mains outage of a few hours 
will not cause any significant error if the clock runs as accurate as 
possible. But if it is set to run slow, it will. That said, mine is 
running slow all the time, but any attempt to correct is rather futile, 
as it just not possible to set the pendulum sufficiently accurate. It 
needs a fine adjustment, which whould not be hard to make.

Of course, for the utmost accuracy one would run any crystal oscillator 
24/7 and not want any breaks in power. But I think the mechanical play 
on the hands is more significant than errors in the crystal oscillator - 
at least on my clock.

I believe Big-Ben in the UK can be corrected by adding pennies to it, so 
providing an upwards force. That is what I am told, but I must admit it 
seems a bit unlikely. Perhaps possible if there are a lot of pennies 
there. Apparently this is done, as it allows corrections without 
stopping the clock.

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