Tri-clamp displacers and engine heads: 1.5, 2 and 3 in spools

sizes

9 in table

Notes

• Displacer diameter = bore − 2 × gap: 1.5 in → Ø33.6, 2 in → Ø46.0, 3 in → Ø70.9. Length 1.5–2.5 × bore (the longer, the bigger the temperature difference it can hold across itself); stroke 0.3–0.4 × length. A 2 in × 6 in spool takes the Ø46 × 90 displacer with a 30 mm stroke.
• Shell displacers: 1 mm wall, closed hot end, internal rings every 25 mm, printed open end up (no supports); the cap presses in and carries the Ø3 rod on an M3 grub. Mass matters less than you think at 2–5 Hz; stiffness and straightness matter more. PETG for a cold end under 80 °C; the hot end of the displacer sees the hot plate only by radiation: PETG survives a tea-light engine, use a foam-and-foil or a thin stainless cup over the nose for a burner engine.
• Regenerative (annular-gap) displacer: 1.5 mm gap and 12 slots packed with #100 stainless mesh turn the gap into the regenerator (Senft's LTD trick); use it in a single spool with no separate regenerator section. Foam templates: cut closed-cell foam (EVA, pool noodle) to Ø and length with the cross lines for centring the rod.
• Heads (ISO 2852 caps with features on the back, so a stock clamp and gasket seal them): displacer head (3/32 in brass guide tube press-fit on centre + 4 mm barb), power head (10 mL syringe barrel socket, Ø15.9, as the power cylinder + M5 port), instrument head (DS18B20, K-type and a barb), crank head (Ø3 rod gland with an O-ring groove and two 623 towers 24 mm up for a crankshaft right on the cap). Heads print flat, face down, at 0.15 mm layers; sand the sealing land.
• Engine recipes: Gamma, 2 in: hot ferrule + 6 in spool + displacer head on top, Ø46 × 90 shell displacer, power head with a 10 mL syringe on a side tee or the crank head; flywheel Ø100 on the crank kit. Beta: one spool, regenerative displacer, crank head on the cold end. Free-piston: 2 in spool, Ø46 displacer on the spiral flexures, power piston from the free-piston core.
• LES: this is the shelf the LES engines are literally built from; every head here replaces a flat cap that used to be drilled by hand.

Sizes

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

Long Earth Society	Tri-clamp Stirling engine builds	web, video	LES site
James R. Senft	An Introduction to Low Temperature Differential Stirling Engines (displacer and gap design)	book	Moriya Press verify
Wikipedia	Stirling engine	web	CC BY-SA 4.0 (text)

Free files

★ Free files 46 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

Plain text: sheet.txt · JSON: /api/geometry?object=tri-clamp-displacers-and-heads

Fits with