1/8 speed
Sources and simplifications
  • The bridges are cut back (skeletonised) and the automatic rotor and keyless works are left out so the train can be seen.
  • Tooth counts are chosen so the ratios are exact (centre 1/h, fourth 1/min, escape wheel 16 rpm at 4 Hz); real calibres use similar but not identical counts.
  • Gear teeth are trapezoids, not involute or cycloidal profiles; the escape teeth and pallet stones are simplified clubs and blocks.
  • The balance swing is a sine with a set amplitude; in a real watch amplitude falls as the mainspring runs down, and the impulse is a brief push near the centre.
  • Motion is slowed (default 1/8) so the escapement can be followed; the readout gives real-time rates.

Sources:

Seconds marker on the fourth wheel: once a minuteSkeletonised bridges over the going trainRuby jewels at every pivot and on the palletsA mechanical watch movement from the back, as a three.js scene. It is a 25.6 mm automatic of the ETA 2824 class [5], with the rotor taken off. The wound mainspring turns the barrel, and the going train steps the speed up. The centre wheel turns once an hour and carries the minute hand. The fourth wheel turns once a minute and carries the seconds [3]. The escape wheel then turns 16 times a minute. Without a brake the spring would unwind in seconds. The lever escapement is that brake [2]. The balance wheel and hairspring swing 28,800 beats an hour, 4 times a second [1]. Each time the balance passes its centre, its impulse pin flips the lever. The lever unlocks one tooth of the 15-tooth escape wheel. The tooth slides over a ruby pallet, kicking the balance to keep it swinging, then drops and locks on the other pallet. Each beat the escape wheel turns half a tooth, 12° [2]. That steady release is what the hands count, and the tick you hear. With 5.8 turns of spring the model runs 39 hours, inside the 36–40 h of a one-day movement [4]. The scene uses brushed bridges and plate, gold-plated wheels and blued, iridescent screws and springs. The jewels are transmissive rubies, and glow shaders mark the impulse and the energy passing down the train each beat. Steps 1–4 highlight each stage, ← → set the slow motion, and W winds the spring.