Watt's linkage (straight-line motion), 60 / 30 / 60 — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/watts-linkage-mechanism/  (CC BY 4.0)
Basis: Xem Studio design following Brown No. 337 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- Two equal radius arms swinging in opposite directions, joined by a short coupler: the coupler's midpoint moves on a figure-eight whose middle part is very nearly straight — Watt's 1784 parallel motion for a beam-driven rod.
- Here: arms 60 mm, coupler 30 mm, fixed pivots ±60 mm apart horizontally and 30 mm vertically. At 12° the midpoint is at x = 0.01 mm (straight line x = 0); over ±10° of arm swing it stays within about 0.1 mm of the line.
- Brown's No. 337 (radius rod on the lower end of a short link hung from the beam, rod at its centre); the same linkage locates car axles sideways.
- Parts (each has its own page): four-bar-links, watt-linkage-coupler-30, dowel-pins-metric.
- Brown's movement No. 337 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
radius arms  2 × 60 mm
coupler  30 mm
fixed pivots  (−60, 15) and (60, −15) mm
tracer  coupler midpoint

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. 337: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_337.html

Free files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/watts-linkage-mechanism/index.json
API: https://xemstudio.com/api/geometry?object=watts-linkage-mechanism