# Thermoacoustic fin sleeve for the flame-shroud band: 2 in tube, 34 mm, fins to Ø72, ears inside Ø73

> What fin sleeve fits inside the thermoacoustic flame shroud?

- Category: Stirling engines › Thermoacoustic & fluidyne
- Kind: Hardware
- Basis: Design values: the band of ta-shroud-2in-front / -back is Ø75 inside (r 37.5) and 35 between its end walls; the sleeve, its ears, M4 heads and nuts stay inside r 37
- Page: https://xemstudio.com/objects/thermoacoustic-shroud-fin-sleeve/ · JSON: https://xemstudio.com/api/geometry?object=thermoacoustic-shroud-fin-sleeve · Plain text: https://xemstudio.com/objects/thermoacoustic-shroud-fin-sleeve/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.** 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

- Two halves clamped round a plain 2 in tube over a hot exchanger, inside the flame shroud's band: the flame gas from the flue passes between the fins, the fins conduct into the tube wall and the wall into the exchanger inside.
- Everything stays inside the band: fins to r 36, ears to r 36, the M4 × 12 head and nut at x ±32 inside r 37; 34 long in the band's 35. No fin within ±20° of the ears, so the screw head and nut have room.
- Optional: the engine runs without it (the flame heats the bare tube). Fits: bore clamps the tube (1 mm split take-up); ear holes M4 clearance.

## 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 |
|---|---|---|---|---|
| bore | Ø50.8 | 2 in tube outside over the hot exchanger | clamp | all |
| split | 1.0 total (0.5 per half) | the other half | clamp | all |
| ear holes | Ø4.5 at x ±32 | M4 clearance (ISO 273 medium) | designed | all |
| fins and ears | to r 36 | flame shroud band's chamber wall at r 37.5 (no contact) | designed | all |

## Sizes

| part | bore_mm | length_mm | fins | fin_tip_dia_mm | ears_to_r_mm | screws |
|---|---|---|---|---|---|---|
| ta-fin-sleeve-half-2in-34-r36 | 50.8 | 34.0 | 20 per sleeve, 1.5 thick | 72.0 | 36.0 | 2 × M4 × 12 + nuts |

## Where the files are

- Xem Studio: [tools/gen_ta_modular.py: the section geometry, the network model and every number on these pages](https://xemstudio.com/) — code — CC BY 4.0
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

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

Index: https://xemstudio.com/files/hardware/thermoacoustic-shroud-fin-sleeve/index.json

- ta-fin-sleeve-half-2in-34-r36: [STEP](https://xemstudio.com/files/hardware/thermoacoustic-shroud-fin-sleeve/ta-fin-sleeve-half-2in-34-r36.step) · [STL](https://xemstudio.com/files/hardware/thermoacoustic-shroud-fin-sleeve/ta-fin-sleeve-half-2in-34-r36.stl) — fin-sleeve half (y ≥ 0.5): bore Ø50.8, wall 3, radial fins 1.5 thick to Ø72 every 15° (none within ±20° of the ears), 34 long; ears x ±27.9..36 with Ø4.5 at x ±32: fits inside the flame shroud's band

## Questions

**Why not the other fin sleeves?**

Their ears reach r 44, through the band's wall; this one keeps everything inside the band.

## Fits with

- [Build list: Modular free-piston thermoacoustic engine, 2 in tri-clamp (stack sections and a clamp-in linear alternator)](https://xemstudio.com/objects/list-ta-modular-free-piston-2in/)
- [Thermoacoustic hot-head shroud: flame shroud and flue for a vertical 2 in tri-clamp core](https://xemstudio.com/objects/thermoacoustic-hot-shroud/)
- [Thermoacoustic fin sleeve: clamp-on, 2 in tube, 34 mm (optional)](https://xemstudio.com/objects/thermoacoustic-fin-sleeve/)
- [Tri-clamp closed-end spool: 2 in × 152.4 mm (6 in) with a welded closed end](https://xemstudio.com/objects/tri-clamp-closed-end-spool/)