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

> How does an eccentric drive a yoke?

- Category: Mechanisms › Linkages
- Kind: Hardware
- Basis: Xem Studio design following Brown No. 90 (1868)
- Page: https://xemstudio.com/objects/eccentric-and-slotted-yoke-mechanism/ · JSON: https://xemstudio.com/api/geometry?object=eccentric-and-slotted-yoke-mechanism · Plain text: https://xemstudio.com/objects/eccentric-and-slotted-yoke-mechanism/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

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

## 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.

## Sizes

| parameter | value |
|---|---|
| eccentric | Ø30, 5 mm offset (catalog part) |
| stroke | 10 mm |
| yoke slot | 30 mm |

## Where the files are

- Henry T. Brown (1868, public domain): [Five Hundred and Seven Mechanical Movements — scan on archive.org](https://archive.org/details/fivehundredseven00browiala) — web — Publisher's page; dimensions are facts
- 507movements.com: [Brown's movement No. 90: figure, his text and an animation](https://507movements.com/mm_090.html) — web — Publisher's page; dimensions are facts

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/eccentric-and-slotted-yoke-mechanism/index.json

- eccentric-and-slotted-yoke-mechanism-assembly: [STEP](https://xemstudio.com/files/hardware/eccentric-and-slotted-yoke-mechanism/eccentric-and-slotted-yoke-mechanism-assembly.step) · [STL](https://xemstudio.com/files/hardware/eccentric-and-slotted-yoke-mechanism/eccentric-and-slotted-yoke-mechanism-assembly.stl) — Assembled mechanism, all parts placed at one pose (STEP keeps each part separate)

## 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.

## Fits with

- [Eccentric sheaves Ø30 at 3, 5 and 8 mm offset](https://xemstudio.com/objects/eccentric-sheaves/)
- [Slotted yoke for a Ø30 eccentric (30 mm slot), with rod](https://xemstudio.com/objects/eccentric-slotted-yoke-30/)
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/)