[time-nuts] Pendulums & Atomic Clocks & Gravity
brooke at pacific.net
Sat May 26 22:23:46 EDT 2007
Yes, it has an invar rod pendulum. I haven't taken it apart but expect there
are compensating metals being used. I've heard a well tuned version of this
clock lost 15 seconds in 70 days. But in use the USNO supplied a synchronizing
pulse on the hour so they really only needed to run for an hour. See:
C:\Webdocs_Hosted\I\SWCC.shtml for the self winding clock and
http://tycho.usno.navy.mil/history.html for some USNO history.
The clock above has just minute and hour hands but the movement is designed to
also support a second hand. I have another clock coming that has the second
hand. The Self Winding design is still being used in the London underground.
These are not what's a called precision clock, but rather are what I'd call
functional commercial clocks. In-between consumer clocks and precision clocks.
As far as I can tell the Russion Fedchenko observatory clock was the ultimate.
About 2 milliseconds per day.
Mike S wrote:
> At 07:49 PM 5/26/2007, Brooke Clarke wrote...
>>Back in the 1800s clock makers found ways to temperature compensate
>>pendulum such as putting a Mercury thermometer at the bottom, using
>>dissimilar expansion coefficients (Harrison used steel and bronze (no
>>then)) or materials with almost zero COE like Invar.
>>The Dent clock at Greenwich in 1885 had an arenoid type compensator to
>>barometric pressure effects, later clocks were run in vacuum.
> Does your clock (you only stated you were adjusting the bob on a
> pendulum clock) have either feature? The vast majority, I would hazard
> to say, don't.
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