Tri-clamp power piston: ring-less full-bore pistons Ø34.8, Ø47.5 and Ø72.9 — dimension sheet Source: Xem Studio, https://xemstudio.com/objects/tri-clamp-power-piston/ (CC BY 4.0) Basis: 16 ga ASME BPE bores 34.8 / 47.5 / 72.9 mm; piston drawn at the bore diameter; length 1.2 × bore Catalog version: 2026-10-20 Sizes: see table below - A ring-less full-bore piston: no ring and no O-ring, the seal is the fit in the spool bore. The piston is drawn at exactly the bore, Ø34.8 / 47.5 / 72.9; its running fit to the bore (0.02–0.05 mm on diameter for a clearance seal) is listed under Mating features. - Length 42 / 56 / 88 mm (1.2 × bore). Two 8 mm full-diameter lands at the ends carry the fit; between them the body is relieved 0.4 mm on radius. Crown 2.5 mm, skirt wall 1.6 mm, open skirt. - Wrist-pin bosses cross the skirt at 0.42 L (17.6 / 23.5 / 37.0 mm from the open end) with a Ø3 pin bore; the gap between the bosses is 16 mm (1.5 in) or 18 mm (2 and 3 in) for the con-rod small end. - The -rod pistons add a Ø11 × 6 boss under the crown with a Ø3 bore through crown and boss (8.5 long): the Ø3 displacer rod runs through it (beta, rhombic, free-piston layouts). - The 2 in piston is about 16.8 cm³ of material. spool_in bore_mm piston_od_mm length_mm wrist_pin_z_mm files 1.5 34.8 34.8 42 17.6 piston-1.5in, piston-1.5in-rod 2 47.5 47.5 56 23.5 piston-2in, piston-2in-rod 3 72.9 72.9 88 37.0 piston-3in, piston-3in-rod Files elsewhere (not hosted by Xem Studio; license as stated by the publisher): - Long Earth Society: Tri-clamp Stirling engine builds — web, video — LES site — https://longearthsociety.com/engineering/ - James R. Senft: An Introduction to Stirling Engines (piston fit and leakage) — book — Moriya Press [verify license at link] — https://www.stirlingengine.com/ - ASME: BPE tube dimensions (16 ga sanitary tube) — standard — ASME [verify license at link] — https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment Free files (CC BY 4.0, Xem Studio; STEP + STL, 6 parts): https://xemstudio.com/files/hardware/tri-clamp-power-piston/index.json API: https://xemstudio.com/api/geometry?object=tri-clamp-power-piston