Cartwright's parallel motion (twin gears and cranks) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/cartwright-parallel-motion-mechanism/  (CC BY 4.0)
Basis: Xem Studio design following Brown No. 328 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- Two equal gears turn in opposite directions, each with a crank; equal connecting rods join the cranks to the two ends of a crosshead. By symmetry the crosshead's centre can only move on the line midway between the gears: an exact straight line.
- Here: module 1, 30 T gears at 30 mm, cranks 10 mm, rods 60 mm, crosshead pins 30 mm apart; at 35° the crosshead centre is 65.17 mm above the gear centres.
- Brown's No. 328 (Dr. Cartwright, 1787).
- Parts (each has its own page): crank-gear-m1-30t-pin-r10, cartwright-crosshead-30, four-bar-links, dowel-pins-metric.
- Brown's movement No. 328 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
gears  2 × 30 T, module 1, 30 mm centres
crank radius  10 mm
rods  60 mm (four-bar link)
crosshead pins  30 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. 328: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_328.html

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