HTD displacers: Ø240 flat hollow displacers for a 10 in chamber — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/htd-displacers-10in/  (CC BY 4.0)
Basis: Exact geometry: Ø240 shells in the 10 in bore (Ø247.19), 3.6 radial gap
Catalog version: 2026-10-20

Sizes: see table below
- A thin closed shell: 0.5 skins top and bottom and a 0.5 rim, a Ø20 hub through the middle with the rod socket, a Ø1 hole in the top skin so the inside follows the mean pressure (the skins never carry the charge pressure, only the flow's few pascals).
- Mass about 0.57 kg at a density of 7.9 g/cm³ (a lighter shell material scales it). Gap to the bore 3.6 radial: the annulus is the only passage between hot and cold space and the shuttle-loss path (0.5 W air, 2.4 W helium, Martini).
- Heat leaks through the displacer: the rim skin about 44 W and radiation between the skins about 71 W (ε 0.3, no shield); a foil shield inside cuts the radiation.

part  diameter_mm  thickness_mm  stroke_mm  socket_mm
displacer-240x40-rod6  240.0  40.0  8.0  30.0

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- NASA (NTRS, public domain): W. R. Martini, Stirling Engine Design Manual, NASA CR-168088 (1983): shuttle loss — PDF — US Government work, public domain — https://ntrs.nasa.gov/citations/19830022057
- 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/htd-displacers-10in/index.json
API: https://xemstudio.com/api/geometry?object=htd-displacers-10in