Base plate for 1.5, 2 and 3 in tri-clamp Stirling engines — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/tri-clamp-engine-base-plate/  (CC BY 4.0)
Basis: Spool passage = ISO 2852 flange Ø + 2 (50.5 / 64 / 91); width flange + 90, depth max(70, flange + 30); M5 clearance Ø5.5 (ISO 273 medium)
Catalog version: 2026-10-20

Sizes: see table below
- A 6 mm plate with 6 mm corner radii, sized to the tri-clamp flange: 140.5 × 80.5 (1.5 in), 154 × 94 (2 in), 181 × 121 (3 in).
- On centre a passage Ø52.5 / Ø66 / Ø93 (flange Ø + 2) that the spool or its cap goes through without contact.
- Either side, a 16 × 3.4 slot at flange radius + 18 for the crank stands' M3 screws; at the ends, 4 × Ø5.5 holes (50 mm apart across, 12 in from each end) for M5 into 2020 extrusion.

file  plate  spool passage  stand slots at  M5 holes
base-plate-1.5in  140.5 × 80.5 × 6  52.5  ±43.25  4 × Ø5.5, 116.5 × 50
base-plate-2in  154 × 94 × 6  66  ±50  4 × Ø5.5, 130 × 50
base-plate-3in  181 × 121 × 6  93  ±63.5  4 × Ø5.5, 157 × 50

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Wikipedia: Beam engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Beam_engine
- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 3 parts): https://xemstudio.com/files/hardware/tri-clamp-engine-base-plate/index.json
API: https://xemstudio.com/api/geometry?object=tri-clamp-engine-base-plate