Free-piston displacer liner: Ø40 bore, regenerator inner wall, rim clamped in the tri-clamp joint — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/fpse-displacer-cylinder/  (CC BY 4.0)
Basis: Design values of the free-piston generator: displacer bore Ø40.00 (0.30 radial gap to the Ø39.4 displacer), regenerator annulus Ø41.5–Ø47.5, rim at the ISO 2852 flange diameter
Catalog version: 2026-10-20

Sizes: see table below
- It hangs from joint A: its Ø64 × 0.8 rim is clamped between two half gaskets exactly like the flexure leaves, so it is centred by the clamp and sealed by the gaskets; six windows in the rim over r 20.75–23.75 let the gas from the regenerator through to the cooler.
- The tube (Ø40 bore, 0.75 wall) is the regenerator's inner wall and the displacer's bore, from 5 mm above the outer bottom (the gas turns under its end) to the joint.
- Six 10° spokes 2 thick at 73.05–75.05 mm carry the 389 screen rings and centre the tube in the bore; below them the heater insert slides onto the tube from the bottom (optional).
- Fits: bore Ø40 is the displacer's designed 0.30 gap (no contact); spokes and rim OD locate in the Ø47.5 bore and the clamp; the rim is clamped.

feature  value
bore  Ø40.00 (displacer gap 0.30)
tube OD  41.5
rim  Ø64 × 0.8, 6 windows
spokes  6 × 10°, 2 thick, z 73.05–75.05
bottom end  z 5 (2 above the floor)

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Ohio University (Urieli): Stirling cycle machine analysis: ideal adiabatic and simple analysis (after Urieli & Berchowitz, Stirling Cycle Engine Analysis, 1984) — web — author's site — https://www.ohio.edu/mechanical/stirling/
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/fpse-displacer-cylinder/index.json
API: https://xemstudio.com/api/geometry?object=fpse-displacer-cylinder