On 08/05/17 19:14, 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!



This just won't go away, will it :-). Here we are, arguing over the
semantics of phase locked loops, but the term pll didn't come into
wide use until the 1960's, decades after the Shortt clock. I'll
continue to think of it as a hit and miss governor, as it was
originally described...

Chris