Double-sided rack between two equal gears — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/double-rack-two-gears-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 115 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- Two equal gears on fixed shafts 32 mm apart, turning in opposite directions, mesh with the two toothed edges of one rack: the rack is pushed with equal force and speed on both edges, so it runs straight with no side load on its guides.
- Module 1, 20-tooth gears (pitch Ø20) with their axes 10 mm outside each pitch line; one turn moves the rack 62.83 mm. Drawn with the rack one pitch (π mm) along.
- Brown's No. 115 (two equal toothed wheels driving a double rack).
- Parts (each has its own page): double-sided-rack-m1-100-pitch-12, spur-gears-module-1, dowel-pins-metric.
- Brown's movement No. 115 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
gears  2 × 20 T, module 1
shaft centres  32 mm
rack  100 mm, teeth both sides
travel per turn  62.83 mm

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. 115: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_115.html

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