On 05/08/17 20:14, Gareth's Downstairs Computer wrote:
On 05/08/2017 20:06, rickman wrote:

Yes, because it *is* a PLL. In fact the problem most people have with
it is that it doesn't adjust the phase by adjusting the frequency of
the slave. It adjusts the *phase* so clearly it *is* a phase locked loop.

All pendulums have circular error where the frequency is determined by
the amplitude of swing, so for the half cycle where the phase is
adjusted by abridging the swing by the hit of the hit and miss
stabiliser, the frequency of the slave is, indeed, changed.


The standard formula given for the cycle time of pendulums ..

2 * PI * root( L / G)

... is only valid for those small angles where sin( theta ) = theta,
and such angles are so infinitesimal that no visible movement
of a pendulum would be seen!



You seem to be confusing two different things

The error you refer to is due to the pendulum not actually taking a
direct line between the ends of its travel, the error is small for small
amplitudes. There was a famous experiment by a Frenchman in, I think
Paris, he hung a huge pendulum and let it trace its path in sand, rather
than it going 'to and fro' it actually went in arcs as it went to and fro.

The effect is minimised by reducing the amplitude.

As you correctly say, the frequency of a pendulum is given by the
formula you state. If you 'give it a nudge' you may shorted one swing
but the overall frequency is still determined by the formula.

The 'nudge' will change the phase of the swing, not the frequency- ie it
will shorten one cycle.