Tri-clamp crank web: Ø8 bore, Ø3 crank pin at 8, 12 and 18 mm throw — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/tri-clamp-crank-web/  (CC BY 4.0)
Basis: Stroke 16 / 24 / 36 mm (0.46 × bore) for the 1.5 / 2 / 3 in pistons; web Ø = 2 × (throw + 6)
Catalog version: 2026-10-20

Sizes: see table below
- A round crank web: Ø8 shaft bore, Ø3 crank-pin hole at half the stroke, and an Ø2.5 radial hole for an M3 grub onto the shaft. Two webs face each other with the pin between them.
- 1.5 in: Ø28, pin at 8 mm (16 mm stroke). 2 in: Ø36, pin at 12 mm (24 mm stroke). 3 in: Ø48, pin at 18 mm (36 mm stroke). All 5 mm thick.
- Shaft order: tower, web, con-rod, web, tower with 1 mm gaps, inside the crank frame's 21 mm tower gap; the crank pin between the webs is Ø3 × 19.

spool_in  web_od_mm  shaft_bore_mm  pin_hole_mm  throw_mm  stroke_mm  thickness_mm
1.5  28  8  3  8  16  5
2  36  8  3  12  24  5
3  48  8  3  18  36  5

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, 3 parts): https://xemstudio.com/files/hardware/tri-clamp-crank-web/index.json
API: https://xemstudio.com/api/geometry?object=tri-clamp-crank-web