Constant-breadth cam turning in a yoke (three strokes per turn) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/constant-breadth-cam-yoke-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 276 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- A cam of constant breadth (a Reuleaux triangle with rounded corners) turns about its centre between two parallel faces of a yoke exactly its breadth apart, so it touches both at every angle and drives the yoke both ways. Its distance to each face changes from the corner radius to the flank radius: the yoke moves 4.64 mm to and fro three times per turn of the cam.
- Breadth 40 (side 30, corners R5); drawn at 20°, the yoke 2.06 mm from centre.
- Brown's No. 276 (cam giving a reciprocating motion to a bar); the corner-pivoted triangle of No. 91 gives one long stroke with dwells instead.
- Parts (each has its own page): constant-breadth-cam-s30-r5-bore5, constant-breadth-cam-yoke-40, dowel-pins-metric.
- Brown's movement No. 276 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
breadth  40 mm
pivot  centre
stroke  4.64 mm
strokes per turn  3

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. 276: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_276.html

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