Scotch yoke: crank pin in a slotted crosshead on pillar guides — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/scotch-yoke-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 331 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- A crank pin slides in a slot across a crosshead that can only move along two guide pillars: the crosshead position is exactly y = r·sin θ — pure simple harmonic motion, stroke 2r = 24 mm, with no connecting rod.
- Drawn at θ = 40° with the catalog Ø36 crank disc (pin at 12 mm), a Ø3 pin in the 3 mm slot (contact on both faces) and two Ø5 × 100 linear shafts as the guides.
- Brown's No. 331 (crank wrist in a slotted cross-head between pillar guides, as in Nos. 93 and 279).
- Parts (each has its own page): crank-disc-36-pin-r12, scotch-yoke-crosshead-48x14-b5, linear-shafts-h6, dowel-pins-metric.
- Brown's movement No. 331 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
crank radius r  12 mm
stroke  24 mm
motion  y = r sin θ (simple harmonic)
guides  2 × Ø5 shafts, 36 mm apart

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. 331: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_331.html

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/scotch-yoke-mechanism/index.json
API: https://xemstudio.com/api/geometry?object=scotch-yoke-mechanism