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Eccentric in a slotted yoke (harmonic straight-line motion)

How does an eccentric drive a yoke? · Hardware · basis: Xem Studio design following Brown No. 90 (1868)

Also called: eccentric yoke, eccentric scotch yoke, harmonic motion eccentric, excéntrica con yugo ranurado, Exzenter mit Kulisse

Exact dimensions. True size, with no printing tolerance added.

sizes
3 in table

Notes

  • An eccentric (a disc turning about an off-centre shaft) inside a yoke whose two faces touch it: the yoke moves straight with simple harmonic motion, y = e·sin θ, stroke 2e = 10 mm here.
  • It is the eccentric form of the Scotch yoke: no pin, the whole disc is the crank; contact is on the two flat faces.
  • Brown's No. 90 (No. 89 with the strap replaced by a yoke so the rod does not swing).
  • Parts (each has its own page): eccentric-sheaves, eccentric-slotted-yoke-30, dowel-pins-metric.
  • Brown's movement No. 90 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

Eccentric in a slotted yoke size chart

parametervalue
eccentricØ30, 5 mm offset (catalog part)
stroke10 mm
yoke slot30 mm

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

Henry T. Brown (1868, public domain)Five Hundred and Seven Mechanical Movements — scan on archive.orgwebPublisher's page; dimensions are facts
507movements.comBrown's movement No. 90: figure, his text and an animationwebPublisher's page; dimensions are facts

Free files

★ Free files 1 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

eccentric-and-slotted-yoke-mechanism-assemblyAssembled mechanism, all parts placed at one pose (STEP keeps each part separate)STEP · STL
Let your AI pull this. Add https://xemstudio.com/mcp to Claude, ChatGPT, Cursor or any MCP client (free, no account, one minute) and it can look up exact sizes, mating fits and free STEP/STL from every chat.
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Plain text: sheet.txt · JSON: /api/geometry?object=eccentric-and-slotted-yoke-mechanism

Eccentric in a slotted yoke (harmonic straight-line motion), isometric render of a generated part
Render of eccentric-and-slotted-yoke-mechanism-assembly from the free STEP; not to scale.

Fits with

Eccentric sheaves Ø30 at 3, 5 and 8 mm offset, isometric render of a generated part
Eccentric sheaves Ø30 at 3, 5 and 8 mm offset3 sizes★ 3 files
Slotted yoke for a Ø30 eccentric (30 mm slot), with rod, isometric render of a generated part
Slotted yoke for a Ø30 eccentric (30 mm slot), with rod56.0×82.0×8.0 mm★ 1 file
Dowel pins, 2–6 mm (ISO 2338 / DIN 6325), isometric render of a generated part
Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)5 sizes★ 23 files

Questions

How does an eccentric drive a yoke?

An eccentric (a disc turning about an off-centre shaft) inside a yoke whose two faces touch it: the yoke moves straight with simple harmonic motion, y = e·sin θ, stroke 2e = 10 mm here.