Flexure hub washer: Ø12 to Ø26.4 × 2 mm — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/flexure-hub-clamp-washer/  (CC BY 4.0)
Basis: Washer = the leaf hub: Ø hub × leaf bore, 2 mm thick, the same as the rim spacer
Catalog version: 2026-10-20

Sizes: see table below
- A 2 mm washer the size of a leaf's hub, with the leaf's bore, that sits between the two leaf hubs of a stack: as thick as the 2 mm rim spacer between the leaf rims, so both leaves stay flat and parallel.
- Ø12 × Ø4, Ø13.2 × Ø5, Ø17.6 × Ø5, Ø22 × Ø8, Ø26.4 × Ø8 for the Ø40 to Ø120 leaves.

flexure_od_mm  od_mm  bore_mm  thickness_mm
40  12  4  2
60  13.2  5  2
80  17.6  5  2
100  22  8  2
120  26.4  8  2

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- NASA (NTRS, public domain): Free-piston Stirling convertor flexure bearing development and life testing (2005) — PDF — US Government work, public domain — https://ntrs.nasa.gov/search?q=20050182933
- NASA (NTRS, public domain): Flexure bearing design for free-piston Stirling engines (1986) — PDF — US Government work, public domain — https://ntrs.nasa.gov/search?q=19860020334
- NASA (NTRS, public domain): Advanced Stirling Radioisotope Generator (ASRG) engineering unit (2011) — PDF — US Government work, public domain — https://ntrs.nasa.gov/search?q=20110016393
- Wikipedia: Flexure bearing — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Flexure_bearing
- Sunpower (AMETEK): Free-piston Stirling technology overview — web — Sunpower site [verify license at link] — https://sunpowerinc.com/
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 5 parts): https://xemstudio.com/files/hardware/flexure-hub-clamp-washer/index.json
API: https://xemstudio.com/api/geometry?object=flexure-hub-clamp-washer