The
28,800
SheetDrawing Set — Architecture, Escapement, Energy, Tolerances, Revision
Architecture, named.
A mechanical watch is ten components in conversation. Everything else — case, crown, crystal — is furniture around them. Here they are in their relative positions, drawn to scale.
Four steps: wind, release, regulate, display.
Every mechanical watch since 1675 has worked in this order. The rest is refinement.
Wind.
Torque is loaded into a blue steel ribbon. Twirling the crown or swinging your arm both accomplish the same thing: bending a 380 mm strip tighter against itself.
Release.
The barrel's slow unwinding is converted by the gear train into faster and faster rotations. Torque goes down, speed goes up, by a combined ratio of roughly 63:1 by the time we reach the escape wheel.
Regulate.
The escape wheel can't just spin. The pallet fork catches it, lets a single tooth pass, then re-catches. Each catch is a tick. The balance wheel's inertia guarantees that the catches happen at exactly 4 Hz.
Display.
The fourth wheel drives the seconds hand. The centre wheel, through the motion works, drives minutes and hours. The balance wheel decides how fast any of this happens — and therefore decides what "one second" means to this watch.
The heart is the escapement.
A wheel wants to spin. A lever won't let it, except eight times a second. The lever is pushed by the balance, which is pushed by the lever. This circular argument — mechanically embodied — is what makes a watch a watch.
Mainspring torque over 62 h
From full wind, torque drops steeply in the first 4 hours as the spring relaxes. The useful window — where amplitude stays above 240° — is about 62 h. Past that, the watch still runs, but its accuracy opens up.
Rate deviation by position
Gravity pulls the balance slightly off-centre depending on how the watch is held. A well-regulated chronometer-grade movement keeps the spread below ±5 s/day across six test positions.
What passes, what fails.
Every movement is tested for 15 days in six positions at three temperatures. The sheet below is the pass condition.
| PARAMETER | NOMINAL | ALLOWED | MEASURED · S/N 04128 | RESULT |
|---|---|---|---|---|
| Mean rate · 6 positions | 0 s/d | −4 / +6 s·day⁻¹ | +1.2 s·day⁻¹ | PASS |
| Mean variation | 0 s/d | ≤ 2 s/d | 1.4 | PASS |
| Greatest deviation | 0 s/d | ≤ 5 s/d | 3.7 | PASS |
| Temperature (8 → 38 °C) | 0 s/d | ≤ 0.6 s·°C⁻¹ | 0.21 | PASS |
| Amplitude · full wind | 275° | 260° – 310° | 281° | PASS |
| Amplitude · 24 h | ≥ 240° | min 220° | 247° | PASS |
| Beat error | 0.0 ms | ≤ 0.8 ms | 0.3 ms | PASS |
| Power reserve | 62 h | min 58 h | 64.2 h | PASS |
| Water resistance | 10 ATM | ± 0 ATM | 10 ATM · held | PASS |
| Magnetic resistance | — | ≥ 4,800 A/m | 15,000 A/m | PASS |
Four materials do eighty percent of the work.
Brass for bulk, steel for force, ruby for friction, beryllium-copper alloy for the balance. Everything else is a refinement of these four.
A1 · CU Zn 37
Brass plate
Workhorse. Cheap, machinable, non-magnetic, dimensionally stable. Plated with rhodium where decorative, left bare on the underside where torque is transferred.
A2 · Al₂O₃:Cr
Synthetic ruby
Hardness 9 Mohs. Pivots ride in ruby because brass would wear into an oval after months. The ruby is synthetic — Verneuil process — and perfectly uniform.
A3 · Ni-Cr-Mo
Nivarox hairspring
A paramagnetic alloy whose elastic modulus varies with temperature by almost exactly the opposite amount as the balance wheel's expansion. The two errors cancel.
A4 · W-Cu ρ = 14.5
Tungsten rotor
Heavier than lead. Concentrates angular momentum on the rim for efficient winding even with slow wrist motion. Bearings on the rotor are ceramic ball, not jewel.
Where the 24 jewels go — and why.
A "jewel" in a watch is a friction-reducing bearing. A 17-jewel movement is the old minimum; 24 is standard for COSC-grade. More is not better — the right ones in the right places is.
Mechanical vs. quartz — in specs
| PARAM | DRG-4B | QUARTZ · REFERENCE |
|---|---|---|
| Oscillator | Balance · 4 Hz | Tuning fork · 32,768 Hz |
| Accuracy | ±5 s/d | ±1 s/d |
| Parts | ~ 210 | ~ 60 |
| Service interval | 5 years | battery @ 18 mo |
| Expected life | Indefinite w/ service | 20 – 30 yr PCB |
| Power source | Your arm | SR626 cell |
| Cost floor | $ 800 serviceable | $ 10 |
Glossary for the shop floor
| Amplitude | How far the balance swings. More = more immune to knocks, up to ~315°. |
| Beat error | Asymmetry between the two halves of the swing. Heard as a lop-sided tick. |
| Isochronism | The balance keeping the same period at different amplitudes. It never does perfectly. |
| Impulse | The brief moment the lever hands energy to the balance. |
| COSC | Contrôle Officiel Suisse des Chronomètres. External body that verifies the table on Sheet 06. |
| Côtes de Genève | Decorative stripes on bridges. No function; a trade marker. |
| REV | DATE | CHANGE | BY |
|---|---|---|---|
| – | 2016·03·11 | Initial working draft | A. MALKIN |
| A | 2018·08·02 | Moved 4th wheel to relocate seconds sub-dial | A. MALKIN |
| B | 2021·05·19 | Replaced Nivarox-A with Si hairspring for prototype series | J. ROSSET |
| C | 2026·04·14 | Tightened positional tolerances; added magnetic spec | R. PARRA |
| Next | 2026·09 | Planned — ceramic ball bearing auto stage | — |
Approved for assembly line 04B.
All drawings on this set are released to manufacturing at revision C. Retain prior revisions on the closed-stack file. Two signatures required before cutting steel.