[time-nuts] I now have a clock accurate to 10E-6!!!
Thomas A. Frank
ka2cdk at cox.net
Mon Aug 25 07:44:24 EDT 2008
Congratulations, that is a really nice looking clock!
You may have a real gem there. While the movement doesn't look like
anything special, the pendulum looks like a Riefler.
Which is something quite special...sort of like having a Thunderbolt
inside your bedside alarm clock...
On Aug 25, 2008, at 3:40 AM, Jim Palfreyman wrote:
> Hi Folks,
> Well I've had the best weekend since I've just acquired a pendulum
> that used to be a telecommunication time standard in the 50s. It is
> a German
> made Siemens pendulum master clock that is about 150cm high and has a
> full-length seconds pendulum which is about a metre long. It is
> powered by
> 48V to automatically wind the weight up and will maintain time for
> about 8
> hours without power.
> The pendulum has an adjustment to raise and lower the 7.5kg weight to
> calibrate the clock. One full turn of this knob will advance or
> retard the
> clock by 40 seconds per day. It is graduated into 100 divisions
> enabling you
> to adjust it within 0.4 seconds per day. Half way up the pendulum is a
> little tray where you can deposit small weights for your final
> (and most importantly without stopping the pendulum!)
> Even though it's a master clock it is also designed to be
> synchronised to
> another master clock and so there is an armature on the pendulum
> that can be
> steered by a magnetic coil. I have no documentation on this bit,
> but when I
> figure it out I naturally shall be driving it from a 1PPS
> reference. (See
> There are numerous contacts that are designed to open/shut at
> various times
> including every second, every thirty seconds and minute. The photo
> shows the
> mechanism behind the clock face.
> By connecting the seconds contact up to my 5370B I tuned it quite
> quickly to
> be accurate to about a second a day. Which is about 10 microseconds
> pendulum swing! I'm impressed a tick tock clock can do that.
> (Although it
> pales into insignificance compared to what Harrison accomplished.)
> It is beautifully constructed and now one of my prized possessions!
> (I'll put some more photos in another post.)
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