This is an educational reconstruction, not a 100% digital replica. Published dimensions and functions inform it, but the original engineering drawings, surveyed surface geometry, tooth counts and tolerances have not been obtained. A visually detailed reconstruction must not be mistaken for manufacturing evidence.
Revision 2 — inspect before judging Selection no longer changes material colours. Steel, zinc, painted iron, brass, gilding and patinated bronze have separate finishes. These are reference-based appearance estimates, not measured spectral reflectances or certified surface scans.
Assembly The connected presentation.
Wheel detail Moves the camera closer.
Separate layers Displaces the two wheel solids for inspection only; the connector geometry is not a working assembly in that mode.
Side clearance Exposes the finite escape arbor ending before the pendulum tube.
Next phase Advances the real fixed-step mechanical state, not a canned animation.
Watch one release First seeks the next release with the same solver, then displays that release at 0.05× and pauses. The full Clock face view opens in a true frontal, orthographic projection with one dial visible. The small inspector dial uses the same vector artwork and always displays London civil time. The four external 3D dials continue to follow the selected Live London / Mechanical lab mode.
Explore the connected assemblies
Movement Inspect the three trains, barrels, bearings, shafts and weight drive.
Escapement Use Next phase to advance the actual solver through lock, release, lift and impulse, or watch a single release at 0.05×. Side clearance exposes the separated wheel and pendulum planes.
Four dials Examine the common drive and 12:1 motion works.
Belfry Trigger a quarter program and watch external hammers strike fixed bells. Drag to orbit; Shift-drag or right-drag to pan. Click a part or choose it from the inspector. The keys below and wheel zoom work while the 3D view has focus; Esc releases it.
Space Pauses or resumes only the experiment.
R Resets the camera.
X Toggles X-ray.
O Toggles orthographic projection.
N Advances the escapement to its next phase.
1–5 Change assemblies. Exploded views are inspection transforms; they are not operating configurations.
Two clocks, deliberately separate
Live London Drives the four dial hands from a civil-time reference interpreted with Europe/London. The system handles British Summer Time using the browser’s time-zone database, regardless of the viewer’s location. There is no decorative second hand on the real-style dials.
Mechanical lab Drives them from successful escapement releases, labelled as two seconds each. The starting dial setting is seeded from London time once. A stalled or paused experiment can drift or stop. It is never corrected behind the scenes to match the live header.
Source quality matters This page uses the device clock; its absolute accuracy is unknown, and the site offers no separate time reference. Even a network reference would improve only civil-time accuracy: it is not live telemetry from the physical Great Clock. This application cannot observe maintenance stops, hand-setting operations or the actual clock’s instantaneous error. What is established, and what is reconstructed? An auditable reduced-order energy model Iθ̈ + bθ̇ + K sinθ = τ
The pendulum follows this equation with an implicit discrete-gradient integrator at 1/240 s. Free motion transfers kinetic and gravitational potential energy; explicit damping becomes heat. Each successful release debits the going weight, lifts one gravity arm, and transfers an assumed fraction of its falling energy to the pendulum. The rest is dissipated. A weight at the bottom cannot provide another impulse.
E_stored + Q_heat + E_acoustic − E_initial − W_external = residual
Stored energy includes the pendulum, three weights, gravity arms, transfer work and hammers. Heat is accumulated from the modeled loss terms, not assigned afterwards to erase the error. Winding, coin adjustment and a manual nudge are explicit external work. “Last 8 releases” represents a controlled lowering operation and records the removed energy as negative operator work.
Gears and lifting linkages are modeled as quasi-static constraints: their own kinetic energy and real impact elasticity are not resolved. Hammer lifting is quasi-static; hammer descent follows a conservative rotational pendulum. All impact energy leaves the simplified hammer model into assigned heat and acoustic budgets. Those budgets do not predict the real sound field, and speaker output is not an energy calibration.
A 4.4 m simple pendulum would not give the documented four-second period. This reconstruction uses a compound equivalent with I ≈ 4375.446 kg·m², Σmr ≈ 1100.295 kg·m and effective length 3.9766 m. Its small-amplitude period is four seconds; finite amplitude, finite-step unlocking and impulses change its actual rate. The software is not tuned covertly to UTC.
Source register C1 Restoration clockmakers · Big Ben restoration — three trains, restoration evidence, original colours and the existence of full engineering drawings.
C2 Restoration clockmakers · automatic winding — the 1913 epicyclic and maintaining-power winding system.
What a certified twin would require Obtain the restoration engineering drawings and licensed survey data; record each component’s geometry, materials, mass properties, tooth geometry and assembly tolerances; reproduce the complete winding, maintaining-power, countwork and dial transmission systems; implement validated collision/contact and elastic dynamics; compare measured amplitudes, torque, losses, strike timing and environmental response; and connect a timestamped dial / escapement sensor at Westminster. Until then, “100% physically identical” is not a supportable claim.
Download evidence register Check time reference Save canvas PNG
Reconstruction build 2.0 (September 2026), ported to the DigiSim Museum: native WebGL 2 and JavaScript, with no runtime libraries, CDN assets or remote fonts. Documentary links open only when selected.
