Stirling linkage fittings: rod clevises, shaft adapter, 625 crank stands, Ø3 crank discs, rhombic frame heads — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/stirling-linkage-fittings/  (CC BY 4.0)
Basis: The Ø3 rod / Ø5 shaft / 623-625-608 bearing / M3 conventions used across the shelf; rhombic kit plates 80 × 50 with 625 pockets on 32 mm centres and M3 holes at (±20, −15)
Catalog version: 2026-10-20

Sizes: see table below
- These are the parts that were missing between the kits: a plain Ø3 displacer rod had no way to take a con-rod (rod clevis: grub on the rod, 623 end on its pin); the Ø100 flywheel has a Ø8 bore and the gamma crankshaft is Ø5 (shaft adapter); the can-engine stands carry 623s but the gamma shaft needs 625s (crank stands); the crank head's towers take a Ø3 crankshaft and no disc had a Ø3 bore (crank discs b3); the rhombic gear plates had nothing to stand on (rhombic frame head).
- Gamma, 2 in, crank on the base plate: displacer rod Ø3 → rod-clevis-3mm → conrod-50 → cw-crank-disc on a Ø5 shaft in two crank-stand-625-h60 → shaft-adapter-5-to-8 → flywheel-100. Piston side: crosshead-8mm-rod3 (its own clevis) → conrod-40 → second crank disc 90° behind.
- Gamma, crank on the head: head-crank-2in (623 towers, Ø3 shaft) + crank-disc-b3 + conrod-40 to a rod clevis; flywheel-50 (Ø5 bore) needs a Ø3 → Ø5 bushing: use bushing-3x5x6 from the bearing housings entry.
- Beta, rhombic, 2 in: -rod piston + piston plug + 5 mm tube rod → yoke-lower-piston; displacer Ø3 rod through the tube → yoke-upper-displacer; gear frame plates on the rhombic frame head, 625s in the plates, Ø5 shafts, gears meshed 180° apart. Gear axes 70 mm above the ferrule face so the lower yoke clears the plug stub at bottom dead centre (yoke travel 32–48 mm below the gear line).
- Rhombic plates now specify 625 bearings (the earlier note said 623; the gears have Ø5 bores).
- LES: the bits between the kits.

spool  part  use
1.5  rhombic head  gear axes 70 mm above face; plates on M3 × 10
2  rhombic head  gear axes 70 mm above face; plates on M3 × 10
3  rhombic head  gear axes 70 mm above face; plates on M3 × 10
any  rod-clevis-3mm  displacer rod → con-rod (623 end on the Ø3 pin)
any  rod-clevis-5mm-tube  tube piston rod → con-rod
any  shaft-adapter-5-to-8  Ø8 flywheel on Ø5 crank
any  crank-stand-625  40 / 60 mm axis height, 625 bearing
any  crank-disc-b3  for a Ø3 crankshaft: the crank head's 623 towers or the can engine's skewer

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/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 11 parts): https://xemstudio.com/files/hardware/stirling-linkage-fittings/index.json
API: https://xemstudio.com/api/geometry?object=stirling-linkage-fittings