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Free-piston Stirling power piston Ø29.9 × 30 and Ø39.9 × 40

What size is the power piston of a free-piston Stirling engine? · Hardware · basis: Beta free-piston layout; piston drawn at liner bore − 0.1 (0.05 mm radial clearance-seal gap as drawn)

Long Earth Society build part. The LES free-piston test bed: Ø40 core on flexures in a 2 in tri-clamp vessel. 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
2 in table

Notes

  • The ring-less power piston of the free-piston core: Ø29.9 × 30 for the Ø30 liner, Ø39.9 × 40 for the Ø40.
  • As drawn it is 0.1 mm under the bore, a 0.05 mm radial gap: the seal is that gap, with no rings.
  • Hollow with 2 mm walls, open at the top, with a Ø5 bore (fit: slide) for the Ø5 rod in its closed end.

Sizes

filediameterlengthliner boreradial gaprod bore
power-piston-30x3029.930300.055
power-piston-40x4039.940400.055

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.

featureexactmates withfitfiles
rod boresØ5Ø5 rodslideall
power piston in the linerØ30 / Ø40 (= liner bore)cylinder liner bore Ø30 / Ø40runpower-piston-*

Where the files are

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

NASA (NTRS, public domain)Free-piston Stirling engine design and analysis (RE-1000 test results) (1984)PDFUS Government work, public domain
NASA (NTRS, public domain)Dynamics of free-piston Stirling engines (1987)PDFUS Government work, public domain
WikipediaFree-piston enginewebCC BY-SA 4.0 (text)
WikipediaBeale numberwebCC BY-SA 4.0 (text)
Ohio UniversityStirling cycle machine analysis (Urieli), free onlinewebAuthor's site
Long Earth SocietyEngine buildsweb, videoLES site

Free files

★ Free files 2 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

power-piston-30x30power piston Ø30 (= the Ø30 liner bore; clearance-seal running fit) × 30, Ø5 rod boreSTEP · STL
power-piston-40x40power piston Ø40 (= the Ø40 liner bore; clearance-seal running fit) × 40, Ø5 rod boreSTEP · STL

Plain text: sheet.txt · JSON: /api/geometry?object=free-piston-power-piston

Free-piston Stirling power piston Ø29.9 × 30 and Ø39.9 × 40, isometric render of a generated part
Render of power-piston-40x40 from the free STEP; not to scale.

How it fits

Goes in or on

Free-piston cylinder liner Ø30 × 120 and Ø40 × 160in the Ø30 / Ø40 bore

Connects to

Ø5 rods with E-clip grooves, 120 and 150 mmØ5 × 120 rodLinear alternator movermover on the same rodPiston stop bumper Ø30 and Ø40 × 6bumpers at both ends of its travel

Alternatives

Power piston Ø16, 20, 25, 30 with Ø3 wrist-pin bossflanged-liner pistons Ø16–30

You might also need

Free-piston Stirling displacer Ø29 × 75 and Ø39 × 100, isometric render of a generated part
Free-piston Stirling displacer Ø29 × 75 and Ø39 × 1002 sizes★ 2 files
Gas-spring piston Ø14.9 × 15 and Ø19.9 × 20, isometric render of a generated part
Gas-spring piston Ø14.9 × 15 and Ø19.9 × 202 sizes★ 2 files

Questions

What is a clearance seal?

A piston with no rings that seals by running very close to its bore; leakage through the gap over one cycle is kept to a few percent of the swept volume.

What size is the 40 mm free-piston power piston?

Ø39.9 × 40, hollow, Ø5 rod bore, for the Ø40 liner.