Re: Master Clock contact spark quenching

John Hubert

Can anyone explain why we stick with the Synchronome resistor?

I can make a few guesses;
  1. In a Synchronome, the ‘ON period’ is very short - a few hundred milliseconds per minute, so the losses in a resistor (which only occur in the ON period) are similarly low.  In a car it is MUCH higher.
  2. In the pre WW1 days, resistors were easy.  Larger value capacitors were not.
  3. Many higher value capacitors were then both bulky and relatively expensive - and many (all electrolytic types) were polarity sensitive.
  4. The inductance across a car system is near enough fixed - whereas a clock system will vary from system to system (number of dials) - and so ‘one size fits all’ may not be optimised.
  5. The increase in power consumption for a Synchronome was approx 10%, which is not very significant.

Synchronome and G&J used a resistor across each coil (both master movement and slave dials) whereas Gents only fitted a (capacitor based) system in the master - not the slave dials.  Gents do however have very heavy duty contacts.

One manufacturer whom used an interesting ‘different’ approach was the original Princeps system.  A very light contact based on the pendulum rod ‘made’ the contact (there is no spark on the ‘make’) - but the current break was done by a much heavier duty ‘break’ contact - driven by an electromagnet giving a fast break.  The light contact set only opened after the current had already stopped - so never arcs.


On 6 Jan 2021, at 15:22, Andrew Nahum <andrew.nahum@...> wrote:

Can anyone explain why we stick with the Synchronome resistor?

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