Mutilated pinion and double rack (continuous rotation to reciprocation) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/mutilated-gear-double-rack-mechanism/  (CC BY 4.0)
Basis: Xem Studio design following Brown No. 114 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- A pinion with teeth on half its rim turns continuously between two facing racks on one frame: for half a turn it drives the upper rack (frame moves one way 31.42 mm), for the other half the lower rack (frame comes back).
- The toothless half is cut to the root circle so it clears the other rack; the racks are spaced one pitch diameter apart (20 mm) with their teeth in phase, which keeps the hand-over clean (half a turn = 10 pitches each way).
- Brown's No. 114.
- Parts (each has its own page): mutilated-pinion-m1-20t-half, double-rack-frame-120.
- Brown's movement No. 114 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
pinion  module 1, 10 of 20 teeth
rack spacing (pitch lines)  20 mm
stroke  31.42 mm each way

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. 114: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_114.html

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