Tri-clamp flexure leaf: spiral planar spring clamped in a 2 in joint like a gasket (displacer and piston) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/tri-clamp-flexure-leaf/  (CC BY 4.0)
Basis: Leaf stiffness and stress from a 3D Euler-Bernoulli frame model of the spiral arms (rim clamped at the bore, hub rigid), modulus 200 GPa assumed
Catalog version: 2026-10-20

Sizes: see table below
- Each leaf is a flat disc the size of the gasket web (Ø64) with three spiral arms inside the bore. It sits in a tri-clamp joint between two half gaskets whose webs add up, with the leaf, to the Type B gasket's 1.7: the clamp closes on it exactly as on a gasket, and it centres on the Ø64 flange rims.
- Displacer leaf (joint B, 0.5 thick, 3 arms × 3 wide, 400°): axial 730 N/m, radial 40 kN/m, bending stress 14.3 MPa per mm of travel (86 MPa at ±6).
- Piston leaves (joints C and D, 0.8 thick, 3 × 4 wide, 330°, the second turned over for the opposite hand): axial 3949 N/m each, radial 154 kN/m each, 23.3 MPa per mm (117 MPa at the ±5 design stroke, 140 MPa at ±6).
- The two piston leaves hold the piston against the stator's magnetic side pull: about 55 kN/m of negative radial stiffness (estimate) against 308 kN/m from the leaves (5.6 ×).
- The leaf must not fatigue at the stress above for 10⁹ cycles and more: the leaf's material and finish are the builder's choice and the builder's check.

leaf  t_mm  arm_w_mm  sweep_deg  hub_bore_mm  k_axial_N_m  k_radial_kN_m  MPa_per_mm
displacer  0.5  3.0  400  12.0  730  40.0  14.3
piston  0.8  4.0  330  18  3949  154.1  23.3

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- NASA (NTRS, public domain): Wong, Wood & Wilson (2008), Advanced Stirling Convertor (ASC): 88 We, 850 °C hot end, 38 % efficiency, 1.3 kg — PDF — US Government work, public domain — https://ntrs.nasa.gov/api/citations/20080047351/downloads/20080047351.pdf
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 2 parts): https://xemstudio.com/files/hardware/tri-clamp-flexure-leaf/index.json
API: https://xemstudio.com/api/geometry?object=tri-clamp-flexure-leaf