Brass gear over a tide wave Tide Engine Archive

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Diagram gallery

Every diagram on this site is original, hand-coded SVG — drawn by me from mechanism descriptions, never copied, traced, or generated. Fifteen plates, each embedded in its article and collected here for study. Start with the articles they belong to: the beginner's guide and harmonic analysis explainer.

Two tidal constituents adding together A fast small sine wave and a slower sine wave sum into a larger modulated tide curve. M2 (moon, 12.42 h) S2 (sun, 12.00 h) Sum: spring–neap modulation spring neap
Fig. 1 — My sketch of harmonic superposition: the lunar (M2) and solar (S2) waves add. When they align we get spring tides; when they oppose, neaps. Drawn by Daniel.
A pair of meshed gears scaling rotation speed 100 teeth · slow 10 teeth · fast mesh → 10:1
Fig. 2 — A 100-tooth wheel driving a 10-tooth pinion multiplies speed tenfold. Tide machines chained dozens of such pairs to turn one crank into lunar-speed shafts. Drawn by Daniel.
Schematic of Kelvin's first tide-predicting machine hand crank shafts at constituent speeds pulley adder pen on paper roll
Fig. 3 — My reconstruction of the 1872 principle: one crank drives many shafts, each pulley contributes one constituent, the wire sum moves the pen. Drawn by Daniel.
Pulleys adding three motions onto a single wire M2 crankS2 crank K1 cranksum → pen
Fig. 5 — Each crank moves its pulley up and down; the single wire collects every motion. The free end is the predicted height. Drawn by Daniel.
Relative amplitudes of four tidal constituents M2S2 K1O1 moon · 12.42hsun · 12.00h luni-solar · 23.93hmoon · 25.82h
Fig. 6 — Typical open-ocean proportions: M2 dominates, S2 modulates, K1 and O1 shape the daily inequality. Values vary by port. Drawn by Daniel.
A 24-hour predicted tide curve for a harbour highlow 0006 121824h morning high evening high
Fig. 4 — A typical machine output, traced by hand from my own harmonic sketch: two unequal high waters in 24 hours. Drawn by Daniel.
Sun Earth Moon alignment at spring and neap tides springs: aligned neaps: at right angles sun E M sun E M sun + moon pull together → big range pulls oppose → small range
Fig. 7 — Springs at new/full moon (bodies aligned), neaps at the quarters (at right angles). Drawn by Daniel.
A machine-drawn prediction roll with hour ticks hour ticks → ink curve = predicted height Port: Liverpool · Jan 1911 (margin notes)
Fig. 8 — A prediction roll: time runs along the paper, height across it, hour ticks keep the scale honest. Drawn by Daniel.
Five steps of setting up a prediction run 1 wind to zero 2 set amplitudes 3 set phases 4 ink + test 5 run! a full team-day before a single prediction is drawn
Fig. 9 — The setup ritual: zero, amplitudes, phases, ink, run. Full reconstruction in my setup-day article. Drawn by Daniel.
Timeline of mechanical tide predictors, 1872 to 1968 1872 Kelvin10 comps 1879 India20 comps 1912 US No.237 comps 1921 Doodson60+ theory 1968 digitalbrass ends
Fig. 10 — Ninety years on one line, from Kelvin's ten cranks to the digital handover. Full story in the history pillar. Drawn by Daniel.
An estuary distorting the lunar tide into overtides open sea: clean M2 estuary: M2 + M4, MS4… friction + funnelling breed faster children
Fig. 11 — Shallow water distorts the astronomical tide into overtides like M4 — the extra cranks on harbour machines. Drawn by Daniel.
Doodson numbers identifying tidal constituents 255.555M2 273.555S2 165.555K1 each digit encodes one astronomical recipe — Doodson's Dewey decimal for tides
Fig. 12 — Doodson numbers: six digits pin each wave to its exact celestial cause. Key in the glossary. Drawn by Daniel.
Short symmetric wire runs against long wandering ones wandering runs: stretch + drag Hamburg style: short + symmetric less wire, less weather in the machine
Fig. 13 — Hamburg's reform: shorten every run, balance every cascade. Less stretch, happier small constituents. Drawn by Daniel.
Exaggerated backlash between two gear teeth driving tooth driven tooth the gap = lost motion = pen wobble
Fig. 14 — Backlash: the hair of play between teeth, felt as hesitation at every turning point. Drawn by Daniel.
A tide analyser tracing a record into an integrator input: marigram trace follower arm → integrator disc → constants on dials
Fig. 15 — The rare reverse machine: a follower traces the recorded tide while integrators weigh each constituent. Drawn by Daniel.

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These diagrams are my original work. Short excerpts with attribution and a link are welcome; full republication needs permission — see the Terms of Use. Found an error in a figure? Tell me; corrections are published with credit.