Variable-crank disc Ø80 × 6 with a 6 mm Archimedean spiral slot (R8 → R34 in one turn) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/variable-crank-disc-spiral-slot-80/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance
Catalog version: 2026-10-20

Overall (mm): length 80.0, width 80.0, height 6.0
- Ø80 × 6 disc with a 6 mm slot along an Archimedean spiral rising 26 mm in one turn: turning it against the radial-slot disc slides the pin in or out, 26/360 mm per degree; clamp it to fix the throw.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

dimension  value
disc  Ø80 × 6, Ø8 bore
spiral  R8 → R34, one turn, 6 mm slot

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Henry T. Brown (1868, public domain): Five Hundred and Seven Mechanical Movements — scan on archive.org — web — Publisher's page; dimensions are facts — https://archive.org/details/fivehundredseven00browiala
- 507movements.com: Brown's movement No. 94: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_094.html
- Xem Studio: drawing — web — Publisher's page; dimensions are facts — https://xemstudio.com/objects/variable-crank-mechanism/

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/variable-crank-disc-spiral-slot-80/index.json
API: https://xemstudio.com/api/geometry?object=variable-crank-disc-spiral-slot-80