# Free-piston cylinder liner Ø30 × 120 and Ø40 × 160

> What size cylinder does a free-piston Stirling core use?

- Category: Stirling engines › Free-piston
- Kind: Hardware
- Basis: Bore 30 / 40, length 4 × bore, 3 mm wall
- Page: https://xemstudio.com/objects/free-piston-cylinder-liner/ · JSON: https://xemstudio.com/api/geometry?object=free-piston-cylinder-liner · Plain text: https://xemstudio.com/objects/free-piston-cylinder-liner/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**Exact dimensions.** Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part.

## Notes

- The bore that the displacer and power piston share in the beta free-piston core: Ø30 × 120 (Ø36 outside) or Ø40 × 160 (Ø46 outside), 3 mm wall.
- The displacer runs in it with a 0.5 mm radial gap, the power piston with 0.05 mm, and the stop bumpers fit its bore (fit: press).

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| rod bores | Ø5 | Ø5 rod | slide | all |

## Sizes

| file | bore | outside | length | wall |
|---|---|---|---|---|
| cylinder-liner-30x120 | 30 | 36 | 120 | 3 |
| cylinder-liner-40x160 | 40 | 46 | 160 | 3 |

## Where the files are

- NASA (NTRS, public domain): [Free-piston Stirling engine design and analysis (RE-1000 test results) (1984)](https://ntrs.nasa.gov/search?q=19840017543) — PDF — US Government work, public domain
- NASA (NTRS, public domain): [Dynamics of free-piston Stirling engines (1987)](https://ntrs.nasa.gov/search?q=19870011457) — PDF — US Government work, public domain
- Wikipedia: [Free-piston engine](https://en.wikipedia.org/wiki/Free-piston_engine) — web — CC BY-SA 4.0 (text)
- Wikipedia: [Beale number](https://en.wikipedia.org/wiki/Beale_number) — web — CC BY-SA 4.0 (text)
- Ohio University: [Stirling cycle machine analysis (Urieli), free online](https://www.ohio.edu/mechanical/stirling/) — web — Author's site
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (2 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/free-piston-cylinder-liner/index.json

- cylinder-liner-30x120: [STEP](https://xemstudio.com/files/hardware/free-piston-core/cylinder-liner-30x120.step) · [STL](https://xemstudio.com/files/hardware/free-piston-core/cylinder-liner-30x120.stl) — cylinder liner Ø30 bore × 120, 3 wall
- cylinder-liner-40x160: [STEP](https://xemstudio.com/files/hardware/free-piston-core/cylinder-liner-40x160.step) · [STL](https://xemstudio.com/files/hardware/free-piston-core/cylinder-liner-40x160.stl) — cylinder liner Ø40 bore × 160, 3 wall

## How it fits

### Connects to
- [Free-piston Stirling displacer Ø29 × 75 and Ø39 × 100](https://xemstudio.com/objects/free-piston-displacer/): displacer inside
- [Free-piston Stirling power piston Ø29.9 × 30 and Ø39.9 × 40](https://xemstudio.com/objects/free-piston-power-piston/): piston inside
- [Piston stop bumper Ø30 and Ø40 × 6](https://xemstudio.com/objects/piston-stop-bumper/): bumpers in the bore

### Alternatives
- [Borosilicate test tubes, 10×75 to 30×200 mm](https://xemstudio.com/objects/borosilicate-test-tubes/): glass tube bores
- [Flanged power cylinder liner Ø16, 20, 25, 30](https://xemstudio.com/objects/power-cylinder-liner/): flanged liners Ø16–30

## Questions

**How long is the free-piston cylinder?**

Four bores: 120 mm for Ø30, 160 mm for Ø40, room for displacer, piston and stops in one bore.

**What runs in the liner?**

The displacer (0.5 mm radial gap) and the power piston (0.05 mm), one behind the other.

## Fits with

- [Free-piston Stirling displacer Ø29 × 75 and Ø39 × 100](https://xemstudio.com/objects/free-piston-displacer/)
- [Free-piston Stirling power piston Ø29.9 × 30 and Ø39.9 × 40](https://xemstudio.com/objects/free-piston-power-piston/)
- [Piston stop bumper Ø30 and Ø40 × 6](https://xemstudio.com/objects/piston-stop-bumper/)
- [Borosilicate test tubes, 10×75 to 30×200 mm](https://xemstudio.com/objects/borosilicate-test-tubes/)
- [Tri-clamp spool (two ferrules on a tube), 1.5 and 2 inch](https://xemstudio.com/objects/tri-clamp-spool/)