# Slider-crank mechanism (crank and connecting rod)

> How does a slider-crank turn rotation into straight-line motion?

- Category: Mechanisms › Linkages
- Kind: Hardware
- Basis: Xem Studio drawing; classic mechanism (Brown No. 92)
- Page: https://xemstudio.com/objects/slider-crank-mechanism/ · JSON: https://xemstudio.com/api/geometry?object=slider-crank-mechanism · Plain text: https://xemstudio.com/objects/slider-crank-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

- A crank of radius r drives a connecting rod of length L whose other end slides on a line through the crank centre. Stroke = 2r (40 mm here).
- Slider position x = r·cosθ + √(L² − r²·sin²θ); the rod ratio L/r (4 here) sets how far the motion departs from simple harmonic.
- It is the piston-engine and pump layout; running backwards (slider drives) it needs a flywheel to pass the dead centres.
- Parts (each has its own page): crank-discs-5mm-bore, connecting-rods-623, crosshead-8mm, crosshead-guide-8mm, pins-3mm. Brown's movement No. 92 shows it (1868).

## Sizes

| parameter | value |
|---|---|
| crank radius r | 20 mm |
| rod length L | 80 mm |
| stroke | 40 mm |
| pins | Ø3 |
| shaft | Ø5 |

## 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

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

Index: https://xemstudio.com/files/hardware/slider-crank-mechanism/index.json

- slider-crank-mechanism-assembly: [STEP](https://xemstudio.com/files/hardware/slider-crank-mechanism/slider-crank-mechanism-assembly.step) · [STL](https://xemstudio.com/files/hardware/slider-crank-mechanism/slider-crank-mechanism-assembly.stl) — Assembled mechanism, all parts placed (STEP keeps each part separate)

## Questions

**How does a slider-crank turn rotation into straight-line motion?**

A crank of radius r drives a connecting rod of length L whose other end slides on a line through the crank centre. Stroke = 2r (40 mm here).

## Fits with

- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/)
- [Connecting rods 30 to 80 mm centres with 623 pockets](https://xemstudio.com/objects/connecting-rods-623/)
- [Crosshead Ø8 × 24 for a Ø3 piston rod](https://xemstudio.com/objects/crosshead-8mm/)
- [Crosshead guide, Ø8 bore × 30](https://xemstudio.com/objects/crosshead-guide-8mm/)
- [Crank and wrist pins Ø3 × 12, 16, 19, 20 and 23](https://xemstudio.com/objects/pins-3mm/)