How Do You Make Gears By Hand?

This episode walks through antikythera mechanism reconstruction step by step, using inscriptions, toolmarks analysis, CT/RTI, and experimental archaeology to anchor each build choice. We show how bronze casting created gear blanks (lost-wax for wheels, open-pour plates for frames), how dividers and scribed circular pitch set tooth counts, and how saw-and-file gear cutting produced the triangular profiles and tolerances visible on fragments. You’ll see arbors, hubs, and spacer tubes that carry coaxial pointers; the pin-and-slot epicyclic unit that models lunar anomaly; and metrology that keeps backlash within bounds. Materials analysis (bronze alloy ranges, wear, possible lubrication) sits alongside workshop techniques to explain ancient precision engineering. We compare reconstruction methods, flag constraints from tooth counts and texts, and clarify what’s firmly evidenced versus still debated—so “how Greeks cut gears” becomes a reproducible method, not a myth.
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⏱ Timestamps
00:00 — Why reconstruction matters: mechanism as engineered object
00:30 — Casting the blanks: lost-wax vs open-pour bronze plates
01:00 — Marking tooth counts: dividers, scribing, circular pitch
01:30 — Cutting teeth: saw + file; triangular profile and tolerances
02:00 — Arbors, hubs, and spacers: concentric tubes & coaxial pointers
02:30 — Pin-and-slot epicyclic: building the lunar anomaly in metal
03:00 — Front dials: zodiac & calendar; pointer sharing and backlash
03:30 — Back spirals: Metonic & Saros; pointer steps and cells
04:00 — Toolmarks & metrology: what CT/RTI reveal on fragments
04:30 — Experimental archaeology: reproducing gear trains today
05:00 — Materials analysis: bronze alloys, wear, lubrication
05:30 — Assembly order & calibration: aligning pointers to sky
06:00 — Error budgeting: play vs binding; where tolerances live
06:30 — Engraving inscriptions: legibility, parapegma as UI
07:00 — Casework & protection: plates, covers, and windows
07:30 — Competing reconstructions: constraints from texts/gears
08:00 — What we still don’t know; paths for future discoveries
08:30 — Takeaways: precision by hand, consistency by design
09:00 — CTA: from fragments to a working astronomical calculator

Sources:

Nature (2006) — Decoding the calculator — https://www.nature.com/articles/natur...

Nature (2008) — Olympiad & eclipse prediction — https://www.nature.com/articles/natur...

Sci Rep (2021) — Model of the Cosmos — https://www.nature.com/articles/s4159...

UCL — Mechanical Cosmos — https://discovery.ucl.ac.uk/id/eprint...

MPIWG — Inscriptions — https://www.mpiwg-berlin.mpg.de/resea...

NAM Athens — Shipwreck & Mechanism — https://www.namuseum.gr/en/temporary_...

#ancienttechnology #archaeology #ancientgreece