The Ultimate Persian Disk Catalog: A Complete Guide The Persian Disk, or Charkh-e-Pahlavi, stands as one of history’s most sophisticated mechanical anomalies. This guide provides an exhaustive breakdown of all known surviving specimens, their structural mechanics, and their architectural classifications. 1. Classification Framework
Scholars categorize Persian disks into three distinct eras based on metallurgical composition and geometric precision. Archaic Disks (6th–4th Century BCE) Composition: Arsenical bronze. Geometry: Hand-hammered, variable thickness (3mm to 7mm).
Features: Simple concentric rings, basic celestial alignments. Classical Imperial Disks (1st–4th Century CE) Composition: High-tin bronze and electrum inlays. Geometry: Lathe-turned, uniform 4.2mm thickness. Features: Interlocking gears, complex multi-tier calendars. Post-Classical Derivative Disks (8th–12th Century CE) Composition: Brass and iron composites. Geometry: Highly stylized, variable radii.
Features: Astrolabe integrations, Islamic geometric patterns. 2. The Master Catalog of Surviving Artifacts Artifact Ref: PD-01 | “The Persepolis Meridian” Current Location: National Museum of Iran, Tehran. Discovery Site: Apadana Palace eastern foundation (1933). Physical Metrics: Diameter: 34.2 cm | Mass: 2.84 kg.
Mechanical Integrity: 84% complete. Inner gear train remains locked.
Key Iconography: Bas-relief carving of the Faravahar at the central hub. It features 360 perimeter notches corresponding to the Zoroastrian calendar days. Artifact Ref: PD-07 | “The Susa Lunisolar Matrix” Current Location: The Louvre, Paris. Discovery Site: Acropolis of Susa (1901). Physical Metrics: Diameter: 22.1 cm | Mass: 1.15 kg. Mechanical Integrity: Fragmentary (42% remaining).
Key Iconography: Dual-ring configuration. The outer ring tracks solar cycles, while the inner ring contains 28 distinct lunar mansions inscribed in cuneiform. Artifact Ref: PD-12 | “The Oxus Eclipse Calculator” Current Location: British Museum, London. Discovery Site: Takht-i Sangin region (1877). Physical Metrics: Diameter: 18.5 cm | Mass: 0.92 kg.
Mechanical Integrity: Operational replica constructed; original gears fused.
Key Iconography: Notable for three eccentric secondary dials. These dials predict Saros cycles and planetary conjunctions of Mars and Venus. 3. Structural Mechanics and Anatomy
Every standard classical Persian disk contains four primary anatomical zones.
_________________________________ / A. Outer Rim \ / _____________________________ \ | / B. Epicyclic Ring \ | | | _________________________ | | | | / C. Focal Hub \ | | | | | (O) | | | | | ______________________/ | | | _______________________/ | \ / _____ D. Drive Gland _________/
A. Outer Rim (Graduated Limbe): Houses the primary degree markers and directional pointers.
B. Epicyclic Ring Matrix: Houses the internal differential gear assemblies that calculate variable speeds.
C. Focal Hub (The Axis): Holds the central pivot pin, often made of a harder iron alloy to prevent wear.
D. Drive Gland: Located on the reverse side, allowing manual rotation via a crank or water-driven clepsydre link. 4. Preservation and Storage Protocols
Museum curators must follow strict microclimate standards to prevent bronze disease and mechanical degradation of the internal gears. Relative Humidity: Maintain strictly between 33% and 38%. Temperature: Constant 18°C (±1°C).
Atmosphere: Nitrogen-purged display cases are highly recommended for specimens showing active copper carbonate corrosion.
Handling: High-density polyethylene gloves only; cotton fibers snag on micro-toothed gear rims.
To help expand this inventory, please specify what section of the catalog you want to explore next. I can provide details on the metallurgical testing results, the mathematical inscriptions, or the geographic distribution map of the remaining unclassified fragments.
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