Eccentric spur gear and pinion on a swinging arm (variable speed) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/eccentric-gear-and-pinion-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 222 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- A 40-tooth gear turns on a shaft 5 mm off its centre; a 20-tooth pinion on a swinging arm follows it, held at the exact 30 mm centre distance by a link from the gear's centre stud. The pinion's speed varies each turn as its contact point moves nearer and farther from the shaft: between about 0.75 and 1.25 of the mean 2 : 1 ratio.
- Drawn at 60° of shaft rotation: gear centre at (2.5, 4.33), pinion at (27.9, 20.29), arm pivot at (50, 0). Module 1, teeth in mesh with no backlash drawn.
- Brown's No. 222 (eccentric wheel with a link in place of the groove of No. 221).
- Parts (each has its own page): eccentric-spur-gear-m1-40t-e5-b5, spur-gears-module-1, swing-arm-30-holes-3-and-6, dowel-pins-metric.
- Brown's movement No. 222 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
gear  40 T, bore 5 mm off centre
pinion  20 T on a 30 mm arm
link  30 mm, centre to centre
speed swing  0.75 – 1.25 × mean

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. 222: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_222.html

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