Flexure hub centring bush: Ø5 and Ø8 OD × Ø3 / Ø5 bore × 6 — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/flexure-hub-centring-bush/  (CC BY 4.0)
Basis: OD = flexure leaf hub bore (Ø5 for Ø60/Ø80 leaves, Ø8 for Ø100), ID = rod or tube, 6 long = two 2 mm leaf hubs and the 2 mm hub washer between them
Catalog version: 2026-10-20

Sizes: see table below
- A plain sleeve that centres flexure leaves whose hub hole is bigger than the rod: the two leaf hubs and the hub washer between them sit on its OD, the rod runs through its bore, and the two hub collars (bore = rod) clamp its ends.
- Hub-bush-60-b3 and hub-bush-80-b3: Ø5 OD × Ø3 bore × 6 for Ø60 / Ø80 leaves on the Ø3 displacer rod. hub-bush-100-b3: Ø8 × Ø3 × 6. hub-bush-100-b5: Ø8 × Ø5 × 6 for Ø100 leaves on the 5 mm tube piston rod.

file  od_mm  bore_mm  length_mm  for
hub-bush-60-b3  5  3  6  Ø60 leaves, Ø3 rod
hub-bush-80-b3  5  3  6  Ø80 leaves, Ø3 rod
hub-bush-100-b3  8  3  6  Ø100 leaves, Ø3 rod
hub-bush-100-b5  8  5  6  Ø100 leaves, 5 mm tube

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- NASA NTRS: Free-piston Stirling convertor flexure bearing development and life testing — pdf — US Government work — https://ntrs.nasa.gov/citations/20050182933
- Long Earth Society: Tri-clamp Stirling engine builds — web, video — LES site — https://longearthsociety.com/engineering/
- Wikipedia: Free-piston engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Free-piston_engine

Free files (CC BY 4.0, Xem Studio; STEP + STL, 4 parts): https://xemstudio.com/files/hardware/flexure-hub-centring-bush/index.json
API: https://xemstudio.com/api/geometry?object=flexure-hub-centring-bush