Horological Meandering

nickd
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Only part of the story

I suspect that inertia is only part of the story.  It gives you a lot of advantages in a watch that will be shaken and stirred, but there are other factors that come from having a physically larger movement to play with.

In precisions clocks, one of the key things to master is the "strength" and consistency of the restoring force.  The idea being to give the lightest possible shove t keep the pendulum moving, but without going so small that you can't control the impulse.  If you can't control it you can get it consistent and the oscillator suffers.   A precision clock might have a couple of kilos of pendulum bob moving through a degree or two of arc, being impulsed by a gram or two falling through a couple of millimeters.   This is a ratio of impulse to inertia that's many many magnitudes beyond that of a watch. 

There's also the point of making the oscillator do the least possible work to trigger the impulse.  The more work the oscillator has to do to trigger its impulse, the more it's disturbed, adn the more inconsistent the unlocking force, the more the oscillator suffers..   I'm guesing that the unlocking force for the anchor in a small movement is not significantly proportionally less than the locking force of that of a larger movement, but I could well be wrong (no data).

I suspect, but don't know, that you can get a more controlable impulse with a larger movement, and that the impulse can be smaller relative to the inertia as there's proportionally less energy being lost unlocking etc. 

You only have to look at the major improvement in timekeeping from moving to a chronometer escapement to understand the disturbing influence the impulse has on the oscillator.

nick