# Build list: Thermoacoustic standing-wave engine, half-wave, propane, 2 in tri-clamp

> What parts do I need to build a Thermoacoustic standing-wave engine, half-wave, propane, 2 in tri-clamp?

- Category: Stirling engines › Assembled engines
- Kind: List / guide
- Basis: Every part is a free STEP/STL on this site or a standard part with its own page; quantities are the full count, every screw, nut, pin, gasket and clamp; acoustic numbers from the low-amplitude network model in tools/gen_ta_family.py (Rott's equations, Swift).
- Page: https://xemstudio.com/objects/list-ta-standing-half-wave-2in/ · JSON: https://xemstudio.com/api/geometry?object=list-ta-standing-half-wave-2in · Plain text: https://xemstudio.com/objects/list-ta-standing-half-wave-2in/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

- The propane standing-wave engine as a half-wave: closed at both ends, the top closed by the output: a 40 mm loudspeaker cap or the free-piston's linear alternator.
- Numbers: Gas column 747 mm between two closed ends (λ/2) · 242 Hz at 427 °C · onset ≈ 271 °C with the loudspeaker (270 °C with the alternator) · ≈ 0.46 W of sound into a matched end load at 3 kPa at the hot end

## Sizes

| subsystem | object | parts | qty | note |
|---|---|---|---|---|
| None | tri-clamp-cups | cup-2in-133.35 | 1 | closed hot end: a plain 2 in × 133.35 closed-end spool, no joint and no gasket in the flame |
| None | thermoacoustic-hot-fin-sleeve | ta-fin-sleeve-2in-16x80 | 1 | optional heat exchanger: radial-fin sleeve slid over the closed end; without it the flame heats the bare cup and the engine needs more heat to start |
| None | set-screws-metric | set-m4x4 | 3 | optional: hold the fin sleeve (only with the sleeve) |
| None | thermoacoustic-bore-spacer | ta-spacer-2in-60 | 1 | hot-cavity liner: from the closed end to the hot exchanger |
| None | thermoacoustic-heat-exchanger | heat-exchanger-hot-2in | 1 |  |
| None | thermoacoustic-stack | stack-honeycomb-2in-40-c1.5 | 1 |  |
| None | thermoacoustic-heat-exchanger | heat-exchanger-cold-2in | 1 | inside the water jacket |
| None | thermoacoustic-bore-spacer | ta-spacer-2in-8.4 | 1 | gasket lip to the cold exchanger |
| None | thermoacoustic-water-jacket | ta-jacket-half-2in-14 | 2 | optional heat exchanger: water jacket over the cold exchanger, 9.35 below the cup's face; or cool that band any way you like (a wet rag works) |
| None | socket-head-cap-screws-metric | shcs-m4x25 | 2 | optional: jacket ears (only with the jacket) |
| None | hex-nuts-metric | nut-m4 | 2 | optional: jacket ears (only with the jacket) |
| None | hex-nuts-metric | nut-m4 | 4 | hangers |
| None | tri-clamp-torch-stand | torch-stand-40 | 1 | under the cup, 40 below the closed end; the heat source is a propane / butane torch head in the ring |
| None | set-screws-metric | set-m4x10 | 3 | centre the torch head in the ring |
| None | tri-clamp-spool | tc-spool-2in-12in | 2 | resonator: two 12 in spools (both hangers on the lower) |
| None | tri-clamp-gasket | tc-gasket-2in | 2 | Type B: cup to spool, spool to spool |
| None | tri-clamp-clamps | clamp-half-2in | 4 | 2 joints, two halves each |
| None | socket-head-cap-screws-metric | shcs-m5x30 | 4 | two per clamp |
| None | hex-nuts-metric | nut-m5 | 4 | in the clamps' hex traps |
| None | tri-clamp-gasket | tc-gasket-2in | 1 | choose one output, A (loudspeaker): top of the upper spool |
| None | tri-clamp-clamps | clamp-half-2in | 2 | choose one output, A (loudspeaker): 1 joint, two halves each |
| None | socket-head-cap-screws-metric | shcs-m5x30 | 2 | choose one output, A (loudspeaker): two per clamp |
| None | hex-nuts-metric | nut-m5 | 2 | choose one output, A (loudspeaker): in the clamps' hex traps |
| None | thermoacoustic-driver-cap | driver-cap-2in-40mm-speaker | 1 | choose one output, A (loudspeaker): closes the top: the half-wave's second closed end |
| None | loudspeaker-envelope-40mm | speaker-envelope-40mm | 1 | choose one output, A (loudspeaker): 40 mm loudspeaker in the cap's socket, cone toward the gas |
| None | tri-clamp-gasket | tc-gasket-2in | 1 | choose one output, B (linear alternator): top of the upper spool to the 3 in spool |
| None | tri-clamp-clamps | clamp-half-2in | 4 | choose one output, B (linear alternator): 2 joints, two halves each |
| None | socket-head-cap-screws-metric | shcs-m5x30 | 4 | choose one output, B (linear alternator): two per clamp |
| None | hex-nuts-metric | nut-m5 | 4 | choose one output, B (linear alternator): in the clamps' hex traps |
| None | tri-clamp-spool | tc-spool-2in-3in | 1 | choose one output, B (linear alternator): piston cylinder at the resonator end |
| None | tri-clamp-hot-gasket | hot-gasket-2in | 1 | choose one output, B (linear alternator): flat, bore ID, under the flexure head: the piston skirt passes it |
| None | tri-clamp-flexure-head | fp-flexure-head-2in | 1 | choose one output, B (linear alternator): clamps on the 3 in spool, carries flexure stack A |
| None | tri-clamp-power-piston | piston-2in | 1 | choose one output, B (linear alternator): full-bore, closed crown (no rod hole: the resonator stays sealed) |
| None | tri-clamp-piston-plug | fp-piston-plug-2in | 1 | choose one output, B (linear alternator): in the skirt, carries the tube rod |
| None | dowel-pins-metric | dowel-3x16 | 2 | choose one output, B (linear alternator): wrist dowels through bosses and plug legs |
| None | tube-piston-rods-5mm | tube-rod-5x3.4x120 | 1 | choose one output, B (linear alternator): plug to stack B, through stack A and the mover |
| None | linear-alternator-mover | alt-mover-35-2x8-10x3 | 1 | choose one output, B (linear alternator): on the tube rod, centred in the coils |
| None | set-screws-metric | set-m3x3 | 1 | choose one output, B (linear alternator): mover hub grub |
| None | neodymium-disc-magnets | magnet-10x3 | 16 | choose one output, B (linear alternator): row 1 all N out, row 2 all S out |
| None | linear-alternator-bobbin | alt-bobbin-37-2x10 | 1 | choose one output, B (linear alternator): |
| None | linear-alternator-coil | alt-coil-bay | 2 | choose one output, B (linear alternator): one per bay, the second wound the other way |
| None | linear-alternator-back-iron-sleeve | alt-back-iron-sleeve | 1 | choose one output, B (linear alternator): |
| None | linear-alternator-housing | alt-housing-2in-flex80 | 1 | choose one output, B (linear alternator): |
| None | linear-alternator-cap-ring | alt-cap-2in-flex80 | 1 | choose one output, B (linear alternator): |
| None | tri-clamp-flexure-ring | fp-flexure-ring-80 | 1 | choose one output, B (linear alternator): carries stack B |
| None | spiral-flexure-bearing | flexure-80-3arm-w2.5-t2 | 4 | choose one output, B (linear alternator): two per stack, opposite spiral hand |
| None | flexure-stack-spacer | spacer-80-t2 | 2 | choose one output, B (linear alternator): between the leaf rims |
| None | flexure-rim-clamp-plate | clamp-plate-80 | 2 | choose one output, B (linear alternator): on each stack's rims |
| None | flexure-hub-clamp-washer | hub-clamp-80-b5 | 2 | choose one output, B (linear alternator): 2 mm hub washer between the leaf hubs |
| None | flexure-hub-collar | hub-collar-80-b5 | 4 | choose one output, B (linear alternator): two per stack on the tube rod |
| None | threaded-standoffs-metric | standoff-m3x15 | 3 | choose one output, B (linear alternator): head to alternator housing |
| None | threaded-standoffs-metric | standoff-m3x10 | 3 | choose one output, B (linear alternator): alternator cap to the flexure ring |
| None | socket-head-cap-screws-metric | shcs-m3x20 | 3 | choose one output, B (linear alternator): up through head and stack A into the 15 mm standoffs |
| None | socket-head-cap-screws-metric | shcs-m3x10 | 7 | choose one output, B (linear alternator): 3 housing base flange, 4 hub-collar pinch screws |
| None | socket-head-cap-screws-metric | shcs-m3x12 | 3 | choose one output, B (linear alternator): up through the housing's top flange and cap into the 10 mm standoffs |
| None | socket-head-cap-screws-metric | shcs-m3x16 | 3 | choose one output, B (linear alternator): down through stack B and the ring into the 10 mm standoffs |
| None | 2020-aluminum-extrusion | 2020-200 | 2 | rails on the bench |
| None | 2020-aluminum-extrusion | 2020-400 | 2 | uprights; the hangers bolt to their faces |
| None | t-slot-corner-brackets | corner-bracket-20 | 4 | two per upright, front and back, onto its rail |
| None | button-head-screws-metric | button-m5x10 | 8 | bracket screws, a washer each |
| None | flat-washers-metric | washer-m5 | 8 |  |
| None | drop-in-t-nuts | tnut-dropin-20-m5 | 12 | 8 per stand for the brackets, 2 per hanger |
| None | spool-hanger-collars | hanger-2in-tab | 2 | clamps a spool tube; its bar bolts to both uprights |
| None | spool-hanger-collars | hanger-2in-plain | 2 | the other half of each hanger |
| None | socket-head-cap-screws-metric | shcs-m5x16 | 4 | hanger bar into the uprights' T-nuts |
| None | socket-head-cap-screws-metric | shcs-m4x20 | 4 | close each hanger on its tube |

## Where the files are

- G. W. Swift (LANL / Acoustical Society of America): [Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators (Rott's equations, screen relations, DeltaEC)](https://www.lanl.gov/org/ddste/aldps/materials-physics-applications/condensed-matter-magnet-science/thermoacoustics/) — web, software — LANL (verify at link)
- Phys. Rev. (H. Levine, J. Schwinger): [On the radiation of sound from an unflanged circular pipe, Phys. Rev. 73, 383 (1948): end correction 0.6133 a](https://doi.org/10.1103/PhysRev.73.383) — web — journal article; cited (verify at link)
- Xem Studio: [Free-piston Stirling build list and its checked assembly (tools/asm_free-piston-2in.py): the alternator section reused here](https://xemstudio.com/objects/list-free-piston-2in/) — web — CC BY 4.0
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Build order

1. Stand: rails, uprights, brackets; torch stand on the bench at the column axis, ring toward the back.
2. Cup closed end down: 60 liner, hot exchanger, stack, cold exchanger, 8.4 spacer to the lip, all from the face.
3. Optional: fin sleeve over the closed end, three M4 set screws; water jacket halves on the cup 9.35 mm below the face, M4 × 25 each side.
4. Type B gasket, 12 in spool, clamp; Type B gasket, 12 in spool, clamp.
5. Output A: Type B gasket, driver cap with the speaker, clamp.
6. Output B: Type B gasket, 3 in spool, clamp; piston, plug, dowels and tube rod into the 3 in spool; flat gasket, flexure head; stacks, standoffs, alternator and ring as on the free-piston build.
7. Two hangers on the lower 12 in spool; torch head in the ring.

All printed STLs: https://xemstudio.com/objects/list-ta-standing-half-wave-2in/stl-list.txt

## Questions

**What frequency does it run at?**

66 parts, every one a free STEP/STL on this site; see the table and the build order on this page.

**How hot does the head need to get?**

The model starts it at about 271 °C at the hot exchanger; I expect 50–150 °C more on the real engine.

**Which output should I build?**

The loudspeaker cap (A) is simpler and takes about the same sound power in the model; the linear alternator (B) fits exactly but its piston hardly moves at this frequency.

**Why a water jacket?**

The engine runs on the temperature difference across the stack; the jacket holds the cold exchanger near room temperature while the torch heats the other end.

**Do I need the fin sleeve and the water jacket?**

No. Both are optional heat exchangers on the plain cup; without them the engine needs more heat to start. Any cooling of the band over the cold exchanger works, even a wet rag.

## Fits with

- [Thermoacoustic hot-end fin sleeve: radial fins that slide over a 2 in closed-end cup](https://xemstudio.com/objects/thermoacoustic-hot-fin-sleeve/)
- [Tri-clamp cups: closed-end spools (ferrule on a capped tube), 1.5, 2 and 3 in](https://xemstudio.com/objects/tri-clamp-cups/)
- [Thermoacoustic water jacket: 14 mm clamp-on halves for a 2 in tri-clamp tube](https://xemstudio.com/objects/thermoacoustic-water-jacket/)
- [Thermoacoustic bore spacers and liners for 2 in tri-clamp spools: 8.4, 60 and 61.7 mm](https://xemstudio.com/objects/thermoacoustic-bore-spacer/)
- [Thermoacoustic stack for tri-clamp spools: Ø34.8, Ø47.5 and Ø72.9, honeycomb and spiral](https://xemstudio.com/objects/thermoacoustic-stack/)
- [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/)
- [Torch stand for a horizontal tri-clamp hot leg](https://xemstudio.com/objects/tri-clamp-torch-stand/)
- [Build list: Thermoacoustic standing-wave engine, 2 in spools](https://xemstudio.com/objects/list-thermoacoustic-2in/)
- [Thermoacoustic driver cap: ISO 2852 cap with a Ø40 speaker socket, 1.5, 2 and 3 in](https://xemstudio.com/objects/thermoacoustic-driver-cap/)
- [40 mm loudspeaker envelope (the speaker in the thermoacoustic driver cap)](https://xemstudio.com/objects/loudspeaker-envelope-40mm/)
- [Linear alternator mover: Ø35 carrier for 16 Ø10 × 3 magnets](https://xemstudio.com/objects/linear-alternator-mover/)
- [Build list: Free-piston Stirling, 2 in tri-clamp (flexure-suspended)](https://xemstudio.com/objects/list-free-piston-2in/)
- [Build list: Thermoacoustic standing-wave engine, quarter-wave, propane, 2 in tri-clamp](https://xemstudio.com/objects/list-ta-standing-quarter-wave-2in/)