[time-nuts] 1903 Railroad self-Winding / Self-setting Clock
brooke at pacific.net
Sat Nov 1 16:49:07 EDT 2014
The hourly synchronization 1 second wide pulse turns on a second prior to the top of the hour and off at the top.
But . . . . it's not a low voltage pulse, but rather each clock is in a series loop where the external resistance is
more than an order of magnitude higher than the internal resistance of the solenoid. That's because T = L/R for
inductive circuits and using an external resistor lowers the time constant. When you use a DC source that has just
enough voltage to pull in the solenoid the movement is very sluggish, but when there's an external resistor in the
circuit the action is snappy and much stronger (to the point where for slave clocks it makes the difference between
advancing and just wiggling without advancement).
See for example the video at:
An energy efficient approach might be to start charging a large cap a minute prior to the top of the hour then discharge
it through a series power resistor using a one second wide pulse that ends at the top of the hour. Note it takes more
power to correct the clock if it's a couple minutes off than when it's on time, so there needs to be a lot of power in
PS the synchronizer by Ken's clocks uses a 4.5 V supply and is too weak to work on my clocks.
PPS adding the series resistor is also needed in teletype circuits and for the same reason, to get faster action.
Mike Baker wrote:
> Hello, Time-Nutters--
> A friend has a vintage oak-cabinet pendulum movement
> clock made by The Self Winding Clock Company some time
> around 1903. The company was formed in 1886. By the
> early 1900's era, this clock was known for its relative
> accuracy. These clocks were pendulum controlled and
> powered by a rather small and frequently reset
> mainspring that was wound hourly by a set of 1.5 VDC
> dry-cell batteries. In 1890 (?) the Naval Observatory agreed
> to telegraph standard railway time. Western Union,
> which also owned the Self-Winding Clock Company, sold
> these clocks to the railroads and sent the hourly time
> coordinating signals around the country by telegraph.
> My friend has one of the railroad clocks that has the
> Western Union Telegraph hourly resetting option.
> My friend thought it would be an interesting juxtaposition
> of technology from two different eras by creating the
> momentary 3-volt resetting pulse every hour from a
> GPS disciplined oscillator / clock pulse.
> I am wondering what the easiest approach to this might
> be? I suppose I could take the 1-sec pulses from a
> GPSDO (Trimble Thunderbolt ?) and count 3600 of them
> to generate a momentary reset 3VDC signal. In any event,
> I thought I would pass this by the Time-Nuts gang to see
> if any feedback is available as to what the least complicated
> (simplest) way might be to accomplish this.
> Mike Baker
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