Parallel cranks and coupling rods, two pairs at 90° (no dead centre) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/parallel-crank-coupling-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 230 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- Two shafts 80 mm apart each carry two cranks of equal radius; equal rods join crank to crank, so the shafts turn together at exactly the same speed (a parallelogram linkage). One pair alone would jam or flip at its two dead centres (rod in line with the cranks); a second pair set at 90° is at full leverage exactly then, so the drive never stops — no flywheel needed.
- Catalog Ø36 crank discs (pin at 12 mm) and 80 mm links: the rod length equals the shaft distance, which makes every rod parallel to the line of shafts.
- Brown's No. 230 (circular into circular motion by two pairs of connecting rods at right angles); the quartered cranks of locomotive coupling rods.
- Parts (each has its own page): crank-disc-36-pin-r12, four-bar-links, dowel-pins-metric.
- Brown's movement No. 230 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
shaft centres  80 mm
crank radius  12 mm
rods  2 × 80 mm
crank phase  90°
ratio  1 : 1, same direction

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. 230: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_230.html

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