During my recent antique peregrinations I found a clock driven
physical pendulum. Horologists define it as a compound pendulum, as
it has two well defined bobs at the ends of a rod. Such a pendulum
is common when a long period (beat) is required in a small space,
e.g. tower clocks and metronomes. Such are driven by a usual
escapement probably w/ a crutch. I'm not familiar w/ such clocks.
This one was driven by moving the center of mass in the upper bob.
It contained a small pendulum clock! It necessarily required a
compound pendulum. The upper clock containing bob was immediately
above the knife edge the lower bob was v. ~ 50 cm below the knife
edge resulting in a period > 1.4 s.
Since pendula have interested me, I have rather exhaustively searched
the subject and not found the analysis of such. Of course parametric
driving is common, e.g. pumping a swing and varying the rod length
(e.g. O Botafumeiro), but not coupling two pendulua in such a manner.
I examined the rod below the knife edge carefully and note the
adjustment is in the form a two or three metal rods temperature