Crank, slotted arm and toothed sector driving a rack — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/crank-slotted-arm-sector-rack-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 131 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- A crank pin, in a slide block, runs in the slot of an arm pivoted 70 mm from the crank centre: the arm rocks through ±9.9° (sin⁻¹ 12/70). A 60-tooth sector on the same pivot turns with the arm and drives a rack below: the rack moves R × angle = 30 mm × 0.346 rad = 10.4 mm total, each way, with the quick-return timing of the slotted lever.
- Drawn at crank angle 200°: arm at 9.71°, rack 5.08 mm from mid-stroke, teeth meshed on the sector's pitch circle.
- Brown's No. 131 (rectilinear motion of a rack from a crank by a slotted arm and toothed sector).
- Parts (each has its own page): slotted-arm-sector-gear-m1-60t-60deg-b5, gear-rack-m1-120-full-depth, crank-disc-36-pin-r12, slide-block-12x6, dowel-pins-metric.
- Brown's movement No. 131 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
crank radius  12 mm
pivot distance  70 mm
arm swing  ±9.9°
sector  60 T, R30
rack stroke  10.4 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. 131: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_131.html

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