Connect. Hold. Return.

A conventional two-pusher chronograph, explained through a horizontal clutch, column wheel, brake and reset hammers. This is a teaching layout, not a reconstruction of a specific caliber.

Start and stop

The upper pusher alternates between connecting and disconnecting the stopwatch. A coupling wheel swings around the running wheel’s center, maintaining that first connection while approaching or leaving the chronograph seconds wheel. A brake holds the measured reading after stopping. The base watch continues running.

The chosen ratios

The input and chronograph seconds wheels each have 48 teeth, with an 18-tooth intermediate coupling wheel. Two external meshes give the input and output the same direction and average speed. Our seconds hand shares the chronograph wheel’s shaft: one full revolution takes 60 simulated seconds. The six-column control wheel has twelve indexing positions. These counts are choices for this illustration.

Reset

The lower pusher works only after stopping. Each stopwatch counter has a heart cam on its shaft. Hammers press these cams to return both hands to their zero positions. Our animation follows the short angular route to zero; it does not unwind the accumulated number of turns. Reset during measurement is blocked: this is not a flyback chronograph.

The hearts are metal cams, not jewels. Our flat-faced hammers slide through stationary supports fastened to the plate. Real mechanisms also use pivoting hammers; there is no required vertical direction or pointed tip. Both shoulders of the cam establish a repeatable zero. The guides are visible here; the full spring and reset transmission remain simplified.

Count a minute

The optional counter has 30 positions. Each complete measured minute advances it by one mark, so one counter revolution represents 30 minutes. A finger illustrates the transfer near the end of each seconds-hand revolution. This is an intermittent step, not a continuously rotating minute hand.

Separate parts

The slider opens an exploded inspection view: plate, control components, wheels, cams and reset hammers, then hands. The extra spacing reveals layers; it is not an operating clearance or disassembly sequence. Rotation stays synchronized. Return to zero percent to reassemble the mechanism.

What the model simplifies

The going train, mainspring, escapement, hour/minute display and complete supporting bridges are omitted. A continuously turning hand at the left represents the running watch. Geometry, heart profiles, transfer finger and levers are illustrative. Their prescribed movement does not solve contact forces, backlash, springs or exact tooth phase on engagement.

Engagement and stop actions last 0.36 simulated seconds; reset lasts 0.9. These stretched teaching timings and the final half-second minute transfer are not specifications for a real watch. Slower playback scales the shared simulation clock; Pause exhibit freezes it. Independent close-ups are labeled replays and do not alter the user’s measurement.

Sources

• Chronograph mechanism: reset hammers and guide members — linear or circular strokes, flat contact and stable zero.
• Horopedia: The two-pusher chronograph — functional sequence, coupling, control, reset and counters.
• Horopedia: Heart piece — the reset cam and hammer.

Horopedia identifies its English text as an automatic translation. We use the stated principles rather than broad quality comparisons or ambiguous counter-ratio wording.

Verification

Tests cover reset lockout, pause, accumulated timing after restart, independent running-watch motion, seconds and minute-counter rates, reset angles and the coupling wheel’s center distances.