# Thermoacoustic bore spacers and liners for 2 in tri-clamp spools: 8.4, 60 and 61.7 mm

> How do I hold heat exchangers, a regenerator or a stack at the right place inside a 2 inch tri-clamp spool?

- Category: Stirling engines › Thermoacoustic & fluidyne
- Kind: Hardware
- Basis: ASME BPE 2 in bore Ø47.5; ISO 2852 Type B lip 1.95 past the face; inside Ø44 = the regenerator cage bore; lengths from the engine layouts in tools/gen_ta_family.py
- Page: https://xemstudio.com/objects/thermoacoustic-bore-spacer/ · JSON: https://xemstudio.com/api/geometry?object=thermoacoustic-bore-spacer · Plain text: https://xemstudio.com/objects/thermoacoustic-bore-spacer/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

- Thin tubes at the spool bore (Ø47.5 outside, Ø44 inside) that stand between the parts of a thermoacoustic core and hold each one where the acoustic design wants it. Their ends bear on the exchangers' 1.0 mm outer ring and on the gasket lip, so the whole stack is held between the two gasket lips of the spool with nothing loose.
- 8.4: from a gasket lip to an exchanger at 10.35 mm from the face, so the exchanger sits under a 14 mm water jacket that starts 9.35 mm from the face (clear of the clamp).
- 61.7: the loop core's thermal buffer tube liner. In a 6 in spool the stack of parts is lip, 8.4 spacer, exchanger 10, buffer tube 61.7, hot exchanger 10, regenerator 40, exchanger 10, 8.4 spacer, lip: exactly the 148.5 mm between the two lips.
- 60: the hot-cavity liner of the standing-wave engines' closed hot end; it holds the hot exchanger 60 mm off the closed end, which in the model lowers the half-wave engine's onset from about 680 °C (exchanger on the closed end) to about 271 °C.
- Fits: outside slide in the bore; inside is gas passage; the end faces are flat rings.

## 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 |
|---|---|---|---|---|
| outside | Ø47.5 | 2 in tri-clamp spool / head bore | slide | all |
| inside | Ø44 | gas passage (no contact) | designed | all |
| end faces | flat ring Ø44–Ø47.5 | heat-exchanger outer ring, regenerator cage end, Type B gasket lip | designed | all |
| length | 8.4 / 60 / 61.7 | positions of the exchangers, stack and regenerator in the layout | designed | all |

## Sizes

| file | outside_mm | inside_mm | length_mm | use |
|---|---|---|---|---|
| ta-spacer-2in-8.4 | 47.5 | 44.0 | 8.4 | end spacer |
| ta-spacer-2in-60 | 47.5 | 44.0 | 60.0 | hot-cavity liner |
| ta-spacer-2in-61.7 | 47.5 | 44.0 | 61.7 | thermal buffer tube |

## Where the files are

- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (3 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/index.json

- ta-spacer-2in-8.4: [STEP](https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/ta-spacer-2in-8.4.step) · [STL](https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/ta-spacer-2in-8.4.stl) — Ø47.5 / Ø44 × 8.4: end spacer: from the Type B gasket lip (1.95 inside the face) to an exchanger at 8.0
- ta-spacer-2in-60: [STEP](https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/ta-spacer-2in-60.step) · [STL](https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/ta-spacer-2in-60.stl) — Ø47.5 / Ø44 × 60: hot-cavity liner of the standing-wave head: closed end to the hot exchanger
- ta-spacer-2in-61.7: [STEP](https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/ta-spacer-2in-61.7.step) · [STL](https://xemstudio.com/files/hardware/thermoacoustic-bore-spacer/ta-spacer-2in-61.7.stl) — Ø47.5 / Ø44 × 61.7: thermal buffer tube liner of the loop core: hot exchanger to the secondary ambient exchanger

## Questions

**Why does the buffer tube have a liner?**

It is what the hot exchanger and the regenerator stand on: without it they would slide down the empty buffer tube.

**Do the spacers change the acoustics?**

Slightly: the gas passage is Ø44 instead of Ø47.5 over their length; the model on the build lists includes it.

## Fits with

- [Thermoacoustic heat exchangers, hot and cold, parallel plate, for 1.5, 2 and 3 in tri-clamp spools](https://xemstudio.com/objects/thermoacoustic-heat-exchanger/)
- [Regenerator cage for 2 in and 1.5 in tri-clamp spools (Ø47.5 and Ø34.8)](https://xemstudio.com/objects/regenerator-cage/)
- [Tri-clamp cups: closed-end spools (ferrule on a capped tube), 1.5, 2 and 3 in](https://xemstudio.com/objects/tri-clamp-cups/)
- [Build list: Thermoacoustic traveling-wave loop, 2 in tri-clamp](https://xemstudio.com/objects/list-ta-loop-2in/)
- [Build list: Thermoacoustic standing-wave engine, half-wave, propane, 2 in tri-clamp](https://xemstudio.com/objects/list-ta-standing-half-wave-2in/)