# Build list: Thermoacoustic-Stirling ring generator, three 2 in units, pressurised

> What parts do I need to build a Thermoacoustic-Stirling ring generator, three 2 in units, pressurised?

- 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, gasket and clamp. Numbers from the linear network model in tools/gen_ta_power.py (Rott / Swift equations, written from the published method).
- Page: https://xemstudio.com/objects/list-ta-ring-3x2in/ · JSON: https://xemstudio.com/api/geometry?object=list-ta-ring-3x2in · Plain text: https://xemstudio.com/objects/list-ta-ring-3x2in/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 double-acting thermoacoustic-Stirling generator in 2 in tri-clamp: three cores and three free-piston alternators in a loop, charged with helium, one propane / butane torch under a drum.
- Numbers: 3 units · 20 bar helium · 25 Hz · onset 67 °C with the alternators open, 550 °C on the design load · ≈ 90 W electric for ≈ 341 W into the hot exchangers (27 %) at ±8 mm (model)

## Sizes

| subsystem | object | parts | qty | note |
|---|---|---|---|---|
| None | tri-clamp-custom-length-spools | spool-2in-340.7mm | 3 | core, one per unit: plain 2 in tube with full ferrules; exchangers, regenerator and buffer-tube liner inside |
| None | thermoacoustic-bore-spacer | ta-spacer-2in-8.4 | 6 | gasket lip to each ambient exchanger, both ends of each core |
| None | thermoacoustic-slotted-exchanger-insert | hx-insert-2in-14 | 6 | main ambient (top) and secondary ambient (bottom) exchanger of each core |
| None | regenerator-screen-disc-47-5 | screen-disc-47.5-m100 | 1500 | regenerator: 500 per core, 100 mm of 100-mesh × 0.10 screen |
| None | thermoacoustic-slotted-exchanger-insert | hx-insert-2in-12 | 3 | hot exchanger, under each regenerator |
| None | thermoacoustic-buffer-tube-liner | tbt-liner-2in-180 | 3 | thermal buffer tube: hot exchanger down to the secondary exchanger |
| None | tri-clamp-honed-cylinder-spool | spool-2in-6in-honed-48.00 | 3 | piston cylinder under each core |
| None | free-piston-mover-2in | mover-core-2in-130 | 3 | mover core: the piston's magnetic return path and crown |
| None | free-piston-mover-2in | mover-sleeve-48x130 | 3 | mover sleeve: the running surface in the honed bore |
| None | neodymium-block-magnets | magnet-block-30x10x4 | 144 | 48 per mover: four rows of 12, rows alternately N and S outward |
| None | canned-linear-alternator-stator-2in | stator-bobbin-half-2in-112 | 6 | two halves round each honed spool's tube |
| None | canned-linear-alternator-stator-2in | stator-coil-2in-14x7 | 12 | four per alternator, wound in place, alternate hands, in series |
| None | canned-linear-alternator-stator-2in | stator-iron-half-2in-112 | 6 | return-path shell halves, clamp the bobbin to the tube |
| None | socket-head-cap-screws-metric | shcs-m4x16 | 18 | return-shell ears, three each side |
| None | tri-clamp-flexure-carrier | flexure-carrier-2in-60 | 3 | under each cylinder: flexure stack A on its upper ledge, B on its lower |
| None | spiral-flexure-bearing | flexure-40-3arm-w1.6-t0.5 | 12 | two per stack, opposite spiral hand |
| None | flexure-stack-spacer | spacer-40-t2 | 6 | between the leaf rims |
| None | flexure-rim-clamp-plate | clamp-plate-40 | 6 | on each stack's rims |
| None | flexure-hub-clamp-washer | hub-clamp-40-b4 | 6 | between the leaf hubs |
| None | socket-head-cap-screws-metric | shcs-m3x10 | 18 | stack rims into the carrier ledges (tapped M3) |
| None | threaded-rods-metric | rod-m4x195.9 | 3 | mover crown (tapped M4) down through both stacks |
| None | hex-nuts-metric | nut-m4 | 39 | hub nuts (4 per rod), return-shell ears (6 per unit), drum tabs (3), hangers (2 per hanger) |
| None | flat-washers-metric | washer-m4 | 12 | under each hub nut |
| None | tri-clamp-caps-with-welded-boss | cap-2in-x-0.75in-ferrule | 6 | top of each core and bottom of each carrier: the ¾ in lines join here |
| None | tri-clamp-gasket | tc-gasket-2in | 12 | Type B profile at every 2 in joint, rated above the relief setting at the joint's temperature |
| None | sanitary-clamp-elbows | elbow-90-0.75in | 12 | four per line |
| None | sanitary-clamp-spools | spool-0.75in-3in | 6 | bottom run and the riser's lowest spool |
| None | sanitary-clamp-spools | spool-0.75in-6in | 3 | top of each riser |
| None | tri-clamp-custom-length-spools | spool-0.75in-146.7mm | 3 | riser between the tee and the cross |
| None | sanitary-clamp-tees | tee-0.75in | 3 | fill branch |
| None | sanitary-clamp-crosses | cross-0.75in | 3 | gauge and relief branches |
| None | tri-clamp-caps-with-welded-boss | cap-0.75in-x-1-4npt | 9 | close the tee and cross branches; each carries a 1/4 NPT instrument |
| None | npt-thread-envelopes | npt-1-4-male | 9 | 1/4 NPT stems of the fill valve, pressure gauge and relief valve on each line |
| None | sanitary-clamp-gaskets | gasket-0.75in | 42 | Type B profile at every ¾ in joint, rated above the relief setting |
| None | thermoacoustic-burner-drum | drum-ring-lower | 1 | round the three hot zones; its flue comes down to the torch |
| None | thermoacoustic-burner-drum | drum-ring-upper | 1 | vents in the top |
| None | socket-head-cap-screws-metric | shcs-m4x20 | 9 | drum tabs (3), hangers (2 per hanger) |
| None | tri-clamp-torch-stand | torch-stand-40 | 1 | on the bench under the flue; the heat source is a propane / butane torch head in its ring |
| None | set-screws-metric | set-m4x10 | 3 | centre the torch head |
| None | thermoacoustic-water-jacket | ta-jacket-half-2in-14 | 12 | optional: over the two ambient exchangers of each core, two halves each |
| None | socket-head-cap-screws-metric | shcs-m4x25 | 12 | optional: jacket ears |
| None | hex-nuts-metric | nut-m4 | 12 | optional: jacket ears |
| None | thermoacoustic-fin-sleeve | fin-sleeve-half-2in-34 | 6 | optional: over each hot exchanger inside the drum, two halves each |
| None | socket-head-cap-screws-metric | shcs-m4x16 | 6 | optional: fin-sleeve ears |
| None | hex-nuts-metric | nut-m4 | 6 | optional: fin-sleeve ears |
| None | 2020-aluminum-extrusion | 2020-200 | 12 | per stand: two rails on the bench, two uprights |
| None | t-slot-corner-brackets | corner-bracket-20 | 12 | two per upright |
| None | button-head-screws-metric | button-m5x10 | 24 | bracket screws, a washer each |
| None | flat-washers-metric | washer-m5 | 24 |  |
| None | drop-in-t-nuts | tnut-dropin-20-m5 | 30 | 8 per stand for the brackets, 2 for its hanger |
| None | spool-hanger-collars | hanger-2in-tab | 3 | round each flexure carrier's neck: the column hangs from it |
| None | spool-hanger-collars | hanger-2in-plain | 3 |  |
| None | socket-head-cap-screws-metric | shcs-m5x16 | 6 | hanger bars into the uprights |

## Where the files are

- Applied Energy (Z. Wu, G. Yu, L. Zhang, W. Dai, E. Luo): [Development of a 3 kW double-acting thermoacoustic Stirling electric generator, 136, 866-872 (2014): three engines and three linear alternators in a loop, 5 MPa helium, 86 Hz, 1.57 kW electric, 16.8 %](https://doi.org/10.1016/j.apenergy.2014.04.105) — web — journal article; cited (verify at link)
- Applied Energy (T. Bi, Z. Wu, L. Zhang, G. Yu, E. Luo, W. Dai): [Development of a 5 kW traveling-wave thermoacoustic electric generator, 185, 1355-1361 (2017): three-stage looped engine, 6 MPa helium, 650 °C, 4.69 kW at 15.6 %, 18.4 % peak](https://doi.org/10.1016/j.apenergy.2015.12.034) — web — journal article; cited (verify at link)
- J. Acoust. Soc. Am. (S. Backhaus, G. W. Swift): [A thermoacoustic-Stirling heat engine: detailed study, JASA 107(6), 3148 (2000): torus with inertance and compliance, thermal buffer tube, jet pump against Gedeon streaming](https://doi.org/10.1121/1.429343) — web — journal article; cited (verify at link)
- Appl. Phys. Lett. (S. Backhaus, E. Tward, M. Petach): [Traveling-wave thermoacoustic electric generator, APL 85, 1085 (2004): a thermoacoustic-Stirling engine driving linear alternators, 18 % heat to electricity](https://doi.org/10.1063/1.1781739) — web — journal article; cited (verify at link)
- Applied Energy (D. M. Sun, K. Wang, X. J. Zhang, Y. N. Guo, Y. Xu, L. M. Qiu): [A traveling-wave thermoacoustic electric generator with a variable electric R-C load, 106, 377-382 (2013): 3 MPa helium, about 65 Hz, 345 W at 9.3 %, 12.3 % peak; series capacitor on the alternator](https://doi.org/10.1016/j.apenergy.2013.01.051) — web — journal article; cited (verify at link)
- Applied Energy (Z. Yu, A. J. Jaworski, S. Backhaus): [Travelling-wave thermoacoustic electricity generator using an ultra-compliant alternator, 99, 135-145 (2012): atmospheric air, a loudspeaker as the alternator, 11.6 W](https://doi.org/10.1016/j.apenergy.2012.04.046) — web — journal article; cited (verify at link)
- G. W. Swift (Acoustical Society of America / LANL): [Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators (Rott's equations, the energy equation, screen relations; the method behind DeltaEC)](https://www.lanl.gov/org/ddste/aldps/materials-physics-applications/condensed-matter-magnet-science/thermoacoustics/) — web, book — cited (verify at link)
- J. Thermophysics and Heat Transfer (G. W. Swift, W. C. Ward): [Simple harmonic analysis of regenerators, 10(4), 652-662 (1996): stacked-screen friction c1(φ) = 1268 − 3545φ + 2544φ²](https://doi.org/10.2514/3.842) — web — journal article; cited (verify at link)
- Steel & O'Brien: [Clamp ratings (clamp + elastomer gasket assembly): 2 in single-pin 450 psi at 70 °F / 300 psi at 250 °F; high-pressure bolted 1000 / 800 psi](https://www.steelobrien.com/wp-content/uploads/2020/06/SOB-Clamp-Ratings.pdf) — PDF — manufacturer's rating sheet; numbers cited
- NIST Chemistry WebBook: [Thermophysical properties of fluid systems (helium, air): viscosity and conductivity used for the model's fits](https://webbook.nist.gov/chemistry/fluid/) — web — US Government data
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Build order

1. Stands: three short 2020 stands, one behind each column, rails on the bench; each column hangs from a hanger round its flexure carrier's neck.
2. Cores (bottom face down): 8.4 spacer, secondary exchanger, 180 liner, hot exchanger, 500 screen discs, main ambient exchanger, 8.4 spacer; gaskets and 2 in caps with the ¾ in ferrule on top.
3. Drum lower half over the three cores' lower ends before the cylinders go on; fin sleeves (optional) on the hot zones; drum upper half from the top; tabs bolted.
4. Power modules: mover (48 magnets on the core, sleeve over them, M4 rod into the crown) into each honed spool; carrier with stacks A and B threaded on the rod, nuts set so the leaves are flat at mid-stroke; stator halves round each spool, coils wound in place, return shell clamped; each module clamped under its core, a capped ¾ in ferrule under each carrier.
5. ¾ in lines: from under each column, elbow, 3 in spool, elbow up, riser (3 in spool, tee, custom spool, cross, 6 in spool), two elbows over into the top of the next column; caps with the fill valve on the tee, gauge and relief valve on the cross.
6. Water jackets (optional) over the ambient exchangers; torch stand under the flue; charge each line through its fill valve to 20 bar; leak-check; connect each alternator through its capacitor to its load before lighting the torch.

All printed STLs: https://xemstudio.com/objects/list-ta-ring-3x2in/stl-list.txt

## Questions

**How much electricity does it make?**

About 90 W in the model at 20 bar helium and 550 °C, limited by the alternators' ±8 mm stroke; I expect half to two-thirds of that on the built engine.

**Can it run unpressurised?**

It starts at 1 bar only near 511 °C (helium) or 204 °C (air) and makes milliwatts to a fraction of a watt: its pistons and alternators are sized for 20 bar.

**Why helium?**

Same pressure, more power: helium's sound speed and conductivity let the regenerator pass more acoustic power with less loss. Air at 20 bar gives about nine-tenths of helium's output in the model.

**Why three units?**

Each piston must be 120° from the next for the regenerators to see a traveling wave; with three units the pistons themselves do the phasing, and they block the steady flow a loop would otherwise carry.

## Fits with

- [Free-piston mover for a 2 in honed spool: piston and alternator magnets in one, Ø48.00 × 130](https://xemstudio.com/objects/free-piston-mover-2in/)
- [Linear-alternator stator that clamps round a 2 in tri-clamp tube: four coils outside the pressure wall](https://xemstudio.com/objects/canned-linear-alternator-stator-2in/)
- [Tri-clamp honed cylinder spool: 2 in × 6 in, bore finished Ø48.00](https://xemstudio.com/objects/tri-clamp-honed-cylinder-spool/)
- [Tri-clamp flexure carrier: clamp-in 2 in, two Ø40 flexure stacks](https://xemstudio.com/objects/tri-clamp-flexure-carrier/)
- [Thermoacoustic slotted exchanger insert: 2 in bore, 14 and 12 mm](https://xemstudio.com/objects/thermoacoustic-slotted-exchanger-insert/)
- [Regenerator screen disc: Ø47.5, 100 mesh × 0.10 mm wire](https://xemstudio.com/objects/regenerator-screen-disc-47-5/)
- [Thermoacoustic burner drum: one torch heats one or three vertical 2 in tubes](https://xemstudio.com/objects/thermoacoustic-burner-drum/)
- [Tri-clamp spools to a custom length (fabrication spec): 2 in × 340.7 and 310.7 mm, ¾ in × 146.7 and 80.4 mm](https://xemstudio.com/objects/tri-clamp-custom-length-spools/)
- [Tri-clamp end caps with a welded boss (fabrication spec): 2 in cap with a ¾ in ferrule, ¾ in cap with a 1/4 NPT boss](https://xemstudio.com/objects/tri-clamp-caps-with-welded-boss/)
- [Build list: Thermoacoustic-Stirling engine with twin free-piston alternators, 2 in, pressurised](https://xemstudio.com/objects/list-ta-twin-piston-2in/)
- [Build list: Free-piston Stirling, 2 in tri-clamp (flexure-suspended)](https://xemstudio.com/objects/list-free-piston-2in/)