# Build list: HTD engine, 10 in tri-clamp (high-temperature-differential flat engine)

> What parts do I need to build the HTD engine, 10 in tri-clamp (high-temperature-differential flat engine)?

- 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.
- Page: https://xemstudio.com/objects/list-htd-10in/ · JSON: https://xemstudio.com/api/geometry?object=list-htd-10in · Plain text: https://xemstudio.com/objects/list-htd-10in/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 big flat gamma Stirling for a propane burner: a Ø240 displacer in a 10 in welded-bottom cup, a 48 mm power piston in a bored 2 in spool on the cold cap, a 3 in cross crankcase, a Ø400 flywheel and a geared generator; sealed and charged with helium.
- Numbers: Displacer Ø240 × 40, 8 stroke: 362 mL swept · power piston Ø48.00 × 40: 72.4 mL · dead volume 405 mL · swept/dead 0.179 · Schmidt at 650 / 350 K: 1.47 J per cycle in air at 1 bar, 7.3 J in helium at 5 bar abs · heat-transfer-limited best: air 0.39 W at the shaft near 60 rpm, helium 3.9–4.7 W near 150 rpm · generator 3.4–4.2 W at 11 V (helium) · charge 4 bar gauge helium, relief 6 bar gauge · hot face ≤ 450 °C

## Sizes

| subsystem | object | parts | qty | note |
|---|---|---|---|---|
| None | htd-burner-stand-10in | burner-stand-10in | 1 | on the bench over the burner; its ring carries the 10 in clamp |
| None | htd-burner-shroud-10in | burner-shroud-10in | 1 | optional heat exchanger: round the cup's floor, tabs to the legs |
| None | socket-head-cap-screws-metric | shcs-m5x20 | 3 | optional: shroud tabs to the legs |
| None | htd-hot-cup-10in | hot-cup-10in-60.4 | 1 | face up, through the ring; the displacer inside |
| None | htd-displacers-10in | displacer-240x40-rod6 | 1 | Ø240 × 40, 8 stroke, 1.5 from floor and ceiling at the ends |
| None | htd-displacer-rods | displacer-rod-6x356.7 | 1 | M6 into the displacer, up through guide, spool and piston to the clevis |
| None | sanitary-clamp-gaskets-10-12in | gasket-10in | 1 | cup to cold cap |
| None | sanitary-clamp-bolted-clamps-10-12in | clamp-half-10in-m8 | 2 | the 10 in joint, resting on the stand's ring |
| None | socket-head-cap-screws-metric | shcs-m8x40 | 2 | 10 in clamp bolts |
| None | hex-nuts-metric | nut-m8 | 2 | in the 10 in clamp's traps |
| None | htd-cold-caps-10in | cold-cap-10in-main | 1 | 2 in ferrule up |
| None | npt-thread-envelopes | npt-1-8-male | 1 | the working-space gauge's 1/8 NPT stem in the cap's boss (the gauge body is the builder's choice) |
| None | htd-water-tray-10in | water-tray-10in | 1 | optional heat exchanger: on the cap's flat top round the ferrule |
| None | tri-clamp-gasket | tc-gasket-2in | 2 | cap ferrule to bored spool, bored spool to reducer |
| None | tri-clamp-clamps | clamp-half-2in | 4 | two 2 in joints |
| None | htd-bored-power-spool | spool-2in-5in-bored-48.00 | 1 | the power cylinder |
| None | htd-power-pistons | piston-48-rod6 | 1 | crown down, cheeks up |
| None | sanitary-clamp-reducers | reducer-concentric-3inx2in | 1 | small end down |
| None | sanitary-clamp-gaskets | gasket-3in | 4 | reducer to cross, cross to port cap, the two branch caps |
| None | tri-clamp-clamps | clamp-half-3in | 8 | four 3 in joints |
| None | socket-head-cap-screws-metric | shcs-m5x30 | 12 | 2 and 3 in clamp bolts |
| None | hex-nuts-metric | nut-m5 | 15 | clamp nuts (12), shroud tabs (3, optional) |
| None | sanitary-clamp-crosses | cross-3in | 1 | the crankcase: run vertical, branches along the crankshaft |
| None | htd-crankcase-caps-3in | port-cap-3in-3x-npt14 | 1 | top of the cross: fill valve, gauge, relief valve |
| None | npt-thread-envelopes | npt-1-4-male | 3 | the 1/4 NPT stems of the fill valve, gauge and relief valve (bodies are the builder's choice) |
| None | htd-crankcase-caps-3in | bearing-cap-3in-blind-6001 | 1 | −X branch |
| None | htd-crankcase-caps-3in | seal-cap-3in-6001-seal12 | 1 | +X branch: the shaft leaves here |
| None | ball-bearings-metric | bearing-6001 | 3 | blind cap (1), seal cap (2) |
| None | radial-shaft-seal-12x22x7 | shaft-seal-12x22x7 | 1 | in the seal cap's outer housing; rated for the relief pressure |
| None | htd-crank-linkage | shaft-12x76 | 1 | −X shaft |
| None | htd-crank-linkage | shaft-12x210 | 1 | +X shaft |
| None | htd-crank-linkage | crank-web-r8-b12 | 1 | displacer throw |
| None | htd-crank-linkage | crank-web-link-r8-r20 | 1 | between the two con-rods |
| None | htd-crank-linkage | crank-web-r20-b12 | 1 | piston throw |
| None | set-screws-metric | set-m4x6 | 2 | web hubs |
| None | dowel-pins-metric | dowel-5x16 | 4 | two crank pins, the piston pin, the clevis pin |
| None | ball-bearings-metric | bearing-625 | 4 | con-rod eyes |
| None | htd-crank-linkage | conrod-60-625 | 1 | displacer |
| None | htd-crank-linkage | conrod-237-625 | 1 | piston |
| None | htd-crank-linkage | rod-clevis-6-pin5 | 1 | on top of the displacer rod |
| None | set-screws-metric | set-m4x4 | 1 | clevis to rod |
| None | htd-generator-drive | gear-m1-210t-b12 | 1 | on the +X shaft outside the seal cap |
| None | set-screws-metric | set-m4x8 | 1 | gear hub |
| None | htd-flywheel-400 | flywheel-400-b12 | 1 | on the +X shaft end |
| None | set-screws-metric | set-m6x16 | 2 | flywheel hub |
| None | htd-generator-drive | motor-bracket-2208-3in | 1 | on the seal cap's outer face |
| None | socket-head-cap-screws-metric | shcs-m4x12 | 3 | bracket to the seal cap |
| None | gimbal-motor-2208-envelope | gimbal-motor-2208-envelope | 1 | the generator: 2208 gimbal-class outrunner (KV 128), envelope at its published size |
| None | countersunk-screws-metric | csk-m3x8 | 4 | motor base to the bracket, heads in the countersinks |
| None | tri-clamp-generator-step-up-gears | pinion-adaptor-2208 | 1 | on the motor's rotor top |
| None | socket-head-cap-screws-metric | shcs-m2x4 | 4 | adaptor to the rotor |
| None | tri-clamp-generator-step-up-gears | pinion-m1-15t-b6 | 1 | meshes with the 210 T gear, 14 : 1 |
| None | set-screws-metric | set-m3x3 | 1 | pinion grub |

## Where the files are

- Wiley / Ohio University (I. Urieli): [Urieli & Berchowitz, Stirling Cycle Engine Analysis (Adam Hilger, 1984): isothermal (Schmidt) and simple analyses; course pages](https://www.ohio.edu/mechanical/stirling/isothermal/Schmidt.html) — book, web — analysis methods are facts (verify at link)
- J. R. Senft: [An Introduction to Low Temperature Differential Stirling Engines (Moriya Press, 1996); Mechanical Efficiency of Heat Engines (Cambridge, 2007): forced work and the fundamental efficiency theorem](https://www.cambridge.org/core/books/mechanical-efficiency-of-heat-engines/) — book — methods are facts (verify at link)
- Steel & O'Brien: [Sanitary products catalog 2024: 16AMP end caps 10 / 12 in (A 0.480, B 10.570 / 12.570 in); L14AM7 ferrules 1.500 in; clamp ratings 13MHHM, 13MHP, 13ASME](https://www.steelobrien.com/wp-content/uploads/2024/03/Sanitary-2024-FINAL.pdf) — PDF — publisher's catalogue; dimensions cited, nothing copied
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Build order


All printed STLs: https://xemstudio.com/objects/list-htd-10in/stl-list.txt

## Questions

**How much power does the 10 in HTD make?**

In air at 1 bar about 0.39 W at the shaft near 60 rpm; charged with helium at 4 bar gauge about 3.9–4.7 W near 150 rpm, 3.4–4.2 W of it out of the generator.

**What pressure is it charged to?**

4 bar gauge of helium, relief valve at 6 bar gauge. The 10 in joint then carries 21–32 kN; every clamp, gasket and fitting has to be rated above 6 bar at its temperature.

**Why is the hot face a welded cup?**

So there is no gasket or clamp in the flame: the only joint is at the cold cap.

**Why so slow?**

No regenerator, and the gas heats by conduction across its layer; past a couple of hundred rpm the gas temperatures close up and the friction wins.

## Fits with

- [HTD hot cup: 10 in tri-clamp closed-end cup (welded floor)](https://xemstudio.com/objects/htd-hot-cup-10in/)
- [HTD cold caps: 10 in tri-clamp caps with a 2 in ferrule at the centre](https://xemstudio.com/objects/htd-cold-caps-10in/)
- [Two-bolt high-pressure clamps for 10 and 12 in tri-clamp joints](https://xemstudio.com/objects/sanitary-clamp-bolted-clamps-10-12in/)
- [HTD crank and linkage: webs, link web, con-rods, clevis and Ø12 shafts for a 3 in cross crankcase](https://xemstudio.com/objects/htd-crank-linkage/)
- [Ø400 flywheel on a Ø12 shaft](https://xemstudio.com/objects/htd-flywheel-400/)