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Power piston Ø16, 20, 25, 30 with Ø3 wrist-pin boss
What are the dimensions of a power piston for a Stirling engine power cylinder? · Hardware · basis: Piston OD = liner bore (fit: run), length 0.9 × bore; Ø3 rod hole and Ø3 wrist-pin hole
Long Earth Society build part. The power piston and liner on the LES gamma. The engines
Exact dimensions. Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part. Mating features
- sizes
- 4 in table
Notes
- The piston for the flanged liners, drawn at the liner bore exactly: Ø16 × 14, Ø20 × 18, Ø25 × 22, Ø30 × 27, with a 0.5 chamfer at the crown.
- Hollow with 2 mm walls; its closed end has a Ø3 hole (fit: slide) for a Ø3 piston rod.
- Inside the -blank piston, a wrist-pin bar across the bore carries a Ø3 hole (fit: press) at 0.4 × length + 4 from the closed end.
- Two kinds per bore: the -blank piston has a Ø3 rod hole in its crown and a solid wrist-pin bar (for a crosshead and piston rod); the -trunk piston has a closed 2 mm crown and two wrist-pin bosses 7 mm apart, so a 5 mm con-rod's small end (R7 eye) goes straight on its Ø3 wrist pin with 1 mm each side.
Sizes
| file | diameter | length | rod hole | wrist-pin hole |
|---|---|---|---|---|
| piston-16x14-blank | 16 | 14 | 3 | 3 |
| piston-20x18-blank | 20 | 18 | 3 | 3 |
| piston-25x22-blank | 25 | 22 | 3 | 3 |
| piston-30x27-blank | 30 | 27 | 3 | 3 |
Mating features
Drawn at the exact size. Open press, slide, run and socket features by your process's clearance; leave designed gaps and clamp fits as drawn.
| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| piston OD in the liner | Ø16 / Ø20 / Ø25 / Ø30 (= liner bore) | liner bore (lapped clearance seal) | run | piston-* |
| piston rod hole | Ø3 | Ø3 piston rod | slide | piston-* |
| piston wrist-pin hole | Ø3 | wrist-pin-3x16 | press | piston-* |
| trunk-piston boss gap | 7 | 5 mm con-rod small end, R7 eye (no contact) | designed | piston-* |
Where the files are
Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.
| Wikipedia | Crosshead | web | CC BY-SA 4.0 (text) |
| Wikipedia | Piston | web | CC BY-SA 4.0 (text) |
| James R. Senft | Miniature Stirling engine piston fits (LTD book) | book | reference verify |
| Long Earth Society | Engine builds | web, video | LES site |
Free files
★ Free files 8 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json
| piston-16x14-blank | piston Ø16 (= the liner bore; clearance-seal running fit) × 14: Ø3 rod hole and a Ø3 wrist-pin boss | STEP · STL |
| piston-16x14-trunk | trunk piston Ø16 (= the liner bore) × 14: closed 2 mm crown, open skirt, two wrist-pin bosses 7 apart for a 5 mm con-rod's small end, Ø3 wrist pin across the bore 9.6 above the crown face | STEP · STL |
| piston-20x18-blank | piston Ø20 (= the liner bore; clearance-seal running fit) × 18: Ø3 rod hole and a Ø3 wrist-pin boss | STEP · STL |
| piston-20x18-trunk | trunk piston Ø20 (= the liner bore) × 18: closed 2 mm crown, open skirt, two wrist-pin bosses 7 apart for a 5 mm con-rod's small end, Ø3 wrist pin across the bore 11.2 above the crown face | STEP · STL |
| piston-25x22-blank | piston Ø25 (= the liner bore; clearance-seal running fit) × 22: Ø3 rod hole and a Ø3 wrist-pin boss | STEP · STL |
| piston-25x22-trunk | trunk piston Ø25 (= the liner bore) × 22: closed 2 mm crown, open skirt, two wrist-pin bosses 7 apart for a 5 mm con-rod's small end, Ø3 wrist pin across the bore 12.8 above the crown face | STEP · STL |
| piston-30x27-blank | piston Ø30 (= the liner bore; clearance-seal running fit) × 27: Ø3 rod hole and a Ø3 wrist-pin boss | STEP · STL |
| piston-30x27-trunk | trunk piston Ø30 (= the liner bore) × 27: closed 2 mm crown, open skirt, two wrist-pin bosses 7 apart for a 5 mm con-rod's small end, Ø3 wrist pin across the bore 14.8 above the crown face | STEP · STL |
Plain text: sheet.txt · JSON: /api/geometry?object=power-piston
How it fits
Goes in or on
Flanged power cylinder liner Ø16, 20, 25, 30in the liner of the same bore (run)Connects to
Wrist pin Ø3 × 16pin pressed in the boss
Crosshead Ø8 × 24 for a Ø3 piston rodØ3 piston rod to the crosshead
Crank discs for a Ø5 shaft, 10 to 30 mm strokecon-rod on the wrist pin (trunk style)Alternatives
Syringe pistonssyringe pistons
Free-piston Stirling power piston Ø29.9 × 30 and…Ø30 / Ø40 clearance-seal pistonsIn these build lists
Gamma Stirling, 2 in tri-clampHot spool with a shell displacer, a crank head that carries the crankshaft, the …You might also need
Questions
What size piston goes in the 20 mm liner?
Ø20 × 18, drawn at the bore; the fit is run (see Mating features).
Does the piston need a crosshead?
With a crosshead the piston only moves axially; trunk style, the con-rod goes straight on the wrist pin, fine for rods at least 4 × the stroke.