Xem Studiomeasured geometryFree-piston Stirling, 2 in tri-clamp
No crank: displacer rod through the piston, both hung on spiral flexure stacks; the demonstrator NASA's convertors grew from.
Ø46 × 90 displacer · Ø47.3 lapped piston · Ø80 flexures, 2 stacks · 10–20 Hz on printed leaves
19 printed parts · 9 bought lines · all printed STL URLs · Markdown · tick lines as you go (saved in this browser)
| subsystem | object | parts | qty | note | ||
|---|---|---|---|---|---|---|
| Hot end | Tri-clamp cups | cup-2in-90 STEP · STL | 1 | printed for a warm-plate demonstrator; stainless capped spool for flame | ||
| Cylinder | Tri-clamp spool (two ferrules on a tube) | tc-spool-2in-6in STEP · STL | 1 | buy | 16 ga, 47.5 bore | |
| Joints | Tri-clamp end cap and gasket | tc-gasket-2in STEP · STL | 2 | buy | ISO 2852 Type B gaskets on the cold joints | |
| Clamps | Tri-clamp clamps (printable two-bolt) | clamp-half-2in STEP · STL | 4 | two halves per joint; stainless clamp at the flame side | ||
| Displacer | Tri-clamp displacers and engine heads | displacer-shell-2in-90 STEP · STL displacer-cap-2in STEP · STL | 1 | Ø3 rod on the cap's M3 grub | ||
| Power piston | Tri-clamp power pistons and crank linkag | piston-2in-f020-rod STEP · STL lapping-handle-2in STEP · STL | 1 | lap to fit; bushing in the crown | ||
| Piston plug | Tri-clamp free-piston kit | fp-piston-plug-2in STEP · STL | 1 | carries the 5 mm tube rod | ||
| Wrist dowels | Dowel pins | dowel-3x16 STEP · STL | 2 | buy | retain the plug | |
| Rod bushing | Bearing housings and linear supports | bushing-3x5x6 STEP · STL | 1 | buy | dry: graphite-bronze, or sintered bronze degreased in acetone; no oil | |
| Rods | Hobby brass tube (K&S) | brass-5mm STEP · STL | 1 | buy | 5 mm K&S tube piston rod | |
| Displacer rod | Stirling shafts and rods | rod-3x200 STEP · STL | 1 | through the piston bushing and the tube; steel Ø3 for running | ||
| Flexure head | Tri-clamp free-piston kit | fp-flexure-head-2in STEP · STL | 1 | clamps on the spool's open ferrule | ||
| Flexure ring | Tri-clamp free-piston kit | fp-flexure-ring-80 STEP · STL | 1 | stack B, on standoffs | ||
| Stand | Spool hanger collars | hanger-2in-tab STEP · STL hanger-2in-plain STEP · STL | 1 | hangs the engine from a 2020 crossbar over the heat | ||
| Frame rails | Aluminium T-slot extrusion | 2020-100 STEP · STL | 3 | buy | two uprights + crossbar; M5 T-nuts | |
| Leaves | Planar spiral flexure bearings (Sunpower | flexure-80-3arm-w2.5-t2-print STEP · STL | 4 | 2 per stack; alternate spiral hand; steel DXF for a runner | ||
| Stack hardware | Planar spiral flexure bearings (Sunpower | spacer-80-t2 STEP · STL clamp-plate-80 STEP · STL hub-clamp-80-b5 STEP · STL | 2 | one set per stack | ||
| Hub collars | Tri-clamp free-piston kit | hub-collar-80-b5 STEP · STL hub-collar-80-b3 STEP · STL | 2 | two b5 on the tube, two b3 on the displacer rod | ||
| Centring bush | Tri-clamp free-piston kit | hub-bush-80-b3 STEP · STL | 1 | centres stack B's Ø5 hub bores on the Ø3 rod | ||
| Standoffs | Threaded standoffs | standoff-m3x30 STEP · STL | 3 | buy | head to ring | |
| Fasteners | Socket head cap screws | shcs-m3x10 STEP · STL | 12 | buy | rims to head and ring | |
| Heat | Tea lights | tea-light-maxi-58x24 STEP · STL | 1 | buy | or a hot plate under the cup |
Build order
- Print the calibration coupons; set slicer offsets.
- Print the displacer + cap, cup, piston (f020-rod), plug, flexure head, flexure ring, hub collars, centring bush, and the Ø80 printed leaves, spacers, clamp plates and hub washers.
- Lap the piston in the spool; press the bushing into the crown; plug and dowels in; 5 mm tube into the plug.
- Displacer on its Ø3 rod; rod through the piston bushing and up the tube.
- Cup + gasket + spool + gasket + flexure head, clamped.
- Stack A on the tube: collar · leaf · washer · leaf · collar; rims to the head with spacer and clamp plate (3 × M3).
- 3 × M3 × 30 standoffs; flexure ring on top; stack B on the centring bush on the displacer rod, rims to the ring.
- Centre both at mid-stroke before tightening the collars; heat the cup; tap the tube to start.
Agents: each row's object has /api/geometry?object=slug and the MCP tool get_free_files; the STL list above is the whole print job.