Tri-clamp regenerative displacer: Ø31.8, Ø44.5 and Ø69.9 with 12 slots, 1.5 mm gap — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/tri-clamp-regenerative-displacer/  (CC BY 4.0)
Basis: Spool bore minus a 1.5 mm radial gap (Senft annular-gap regenerator); 16 ga ASME BPE bores 34.8 / 47.5 / 72.9 mm
Catalog version: 2026-10-20

Sizes: see table below
- An annular-gap regenerative displacer: the 1.5 mm radial gap between it and the spool is the regenerator path, so one spool with this displacer is a complete engine with no separate regenerator section.
- Sizes: 1.5 in Ø31.8 × 75, 2 in Ø44.5 × 90, 3 in Ø69.9 × 120 mm. Wall 1.5 mm, closed rounded end, open at the cap end.
- Twelve radial slots 1.2 mm wide run through the wall over the middle 70 % of the length (from 15 % to 85 % of L); they are the pockets for the regenerator matrix.
- Its cap has a spigot Ø(D − 3) × 3 into the shell, a Ø D × 1.5 flange and a Ø16 × 6 boss with the Ø3 rod hole; 10.5 mm overall.

spool_in  bore_mm  displacer_od_mm  length_mm  radial_gap_mm  slots
1.5  34.8  31.8  75  1.5  12
2  47.5  44.5  90  1.5  12
3  72.9  69.9  120  1.5  12

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 Low Temperature Differential Stirling Engines (displacer and gap design) — book — Moriya Press [verify license at link] — https://www.stirlingengine.com/
- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine

Free files (CC BY 4.0, Xem Studio; STEP + STL, 6 parts): https://xemstudio.com/files/hardware/tri-clamp-regenerative-displacer/index.json
API: https://xemstudio.com/api/geometry?object=tri-clamp-regenerative-displacer