{
 "version": "2026-10-20",
 "license": "Dimension sheets are written by Xem Studio from the cited sources and are free to use (CC BY 4.0, attribute 'Xem Studio'). Linked files belong to their publishers under the license shown; Xem Studio does not host them. 'license_verified: false' means the license shown is from memory or the publisher's page as last read and should be confirmed at the link before commercial use.",
 "slug": "stirling-linkage-fittings",
 "name": "Stirling linkage fittings: rod clevises, shaft adapter, 625 crank stands, Ø3 crank discs, rhombic frame heads",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Drives & mechanisms",
 "year": null,
 "question": "What small fittings connect a Stirling engine's rods, cranks, flywheel and rhombic drive together?",
 "tags": [
  "clevis",
  "crank stand",
  "shaft adapter",
  "rhombic",
  "gamma",
  "stirling",
  "tri-clamp",
  "long earth society",
  "con-rod"
 ],
 "aliases": [
  "how to connect a displacer rod to a con rod",
  "stirling engine rod clevis",
  "crank stand 625 bearing",
  "flywheel on 5mm shaft adapter",
  "rhombic drive mount tri clamp"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 11,
 "url": "https://xemstudio.com/objects/stirling-linkage-fittings/",
 "sheet_txt": "https://xemstudio.com/objects/stirling-linkage-fittings/sheet.txt",
 "sheet": {
  "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)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "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."
  ],
  "table": {
   "columns": [
    "spool",
    "part",
    "use"
   ],
   "rows": [
    [
     "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"
    ]
   ]
  }
 },
 "sheet_text": "Stirling linkage fittings: rod clevises, shaft adapter, 625 crank stands, Ø3 crank discs, rhombic frame heads — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/stirling-linkage-fittings/  (CC BY 4.0)\nBasis: 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)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- 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).\n- 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.\n- 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.\n- 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).\n- Rhombic plates now specify 625 bearings (the earlier note said 623; the gears have Ø5 bores).\n- LES: the bits between the kits.\n\nspool  part  use\n1.5  rhombic head  gear axes 70 mm above face; plates on M3 × 10\n2  rhombic head  gear axes 70 mm above face; plates on M3 × 10\n3  rhombic head  gear axes 70 mm above face; plates on M3 × 10\nany  rod-clevis-3mm  displacer rod → con-rod (623 end on the Ø3 pin)\nany  rod-clevis-5mm-tube  tube piston rod → con-rod\nany  shaft-adapter-5-to-8  Ø8 flywheel on Ø5 crank\nany  crank-stand-625  40 / 60 mm axis height, 625 bearing\nany  crank-disc-b3  for a Ø3 crankshaft: the crank head's 623 towers or the can engine's skewer\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Long Earth Society: Tri-clamp Stirling engine builds — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 11 parts): https://xemstudio.com/files/hardware/stirling-linkage-fittings/index.json\nAPI: https://xemstudio.com/api/geometry?object=stirling-linkage-fittings\n",
 "sources": [
  {
   "publisher": "Long Earth Society",
   "title": "Tri-clamp Stirling engine builds",
   "url": "https://longearthsociety.com/engineering/",
   "formats": [
    "web",
    "video"
   ],
   "license": "LES site",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "tri-clamp-power-pistons",
  "tri-clamp-displacers-and-heads",
  "rhombic-drive-kit",
  "crank-conrod-flywheel-kit",
  "counterweighted-cranks",
  "power-cylinder-piston-crosshead",
  "gamma-base-plate-and-beam",
  "ball-bearings-metric",
  "shaft-collars-clips-and-shafts",
  "bearing-housings-and-rod-supports",
  "pins-clevises-and-joints",
  "dowel-pins-metric"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "tri-clamp-spool",
     "why": "rhombic frame head clamps on its ferrule"
    },
    {
     "slug": "gamma-base-plate-and-beam",
     "why": "crank stands bolt into the base plate slots"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "nut-weighted-flywheels",
     "why": "Ø5-hub flywheel on the crank stands' shaft"
    },
    {
     "slug": "crank-conrod-flywheel-kit",
     "why": "con-rods onto the clevises; flywheel on the 5→8 adapter"
    },
    {
     "slug": "counterweighted-cranks",
     "why": "crank discs on the shaft in the 625 stands"
    },
    {
     "slug": "rhombic-drive-kit",
     "why": "gear plates onto the rhombic frame head"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "stirling-shafts-and-rods",
     "why": "Ø5 D-flat crankshaft, Ø3 pins, spacers"
    },
    {
     "slug": "ball-bearings-metric",
     "why": "625 in the stands, 623 in the con-rods"
    },
    {
     "slug": "dowel-pins-metric",
     "why": "Ø3 clevis and crank pins"
    },
    {
     "slug": "set-screws-metric",
     "why": "M3 grubs"
    },
    {
     "slug": "shaft-collars-clips-and-shafts",
     "why": "Ø5 crankshaft"
    }
   ]
  }
 ],
 "faq": [
  {
   "q": "How do I connect a plain 3 mm displacer rod to a connecting rod?",
   "a": "Rod clevis: its Ø3 socket (H7/h6) slides on the rod and an M3 grub locks it; the con-rod's 623 end sits in the 5.2 mm gap on a Ø3 pin."
  },
  {
   "q": "The flywheel has an 8 mm bore and my crankshaft is 5 mm. What now?",
   "a": "The Ø5 → Ø8 shaft adapter: a 20 mm sleeve with two grubs, one on the shaft and one under the flywheel's set screw."
  },
  {
   "q": "How does the rhombic drive attach to a tri-clamp spool?",
   "a": "The rhombic frame head clamps on the spool's open ferrule like any cap; its two uprights take the gear frame plates on M3 screws, putting the gear axes 70 mm above the face."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "rod-clevis-3mm",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/rod-clevis-3mm.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/rod-clevis-3mm.stl",
   "note": "clevis for a Ø3 displacer or piston rod: Ø3 socket 12 deep with a tapped M3 grub, 5.2 mm gap, Ø3 pin: takes a con-rod's 623 end"
  },
  {
   "file": "rod-clevis-5mm-tube",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/rod-clevis-5mm-tube.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/rod-clevis-5mm-tube.stl",
   "note": "clevis for the 5 mm tube piston rod: Ø5 socket with a tapped M3 grub, 5.2 mm gap, Ø3 pin"
  },
  {
   "file": "shaft-adapter-5-to-8",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/shaft-adapter-5-to-8.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/shaft-adapter-5-to-8.stl",
   "note": "Ø5 → Ø8 shaft adapter × 20 with two M3 grubs: puts a Ø8-bore flywheel (Ø80–150) on a Ø5 crankshaft"
  },
  {
   "file": "crank-stand-625-h40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-stand-625-h40.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-stand-625-h40.stl",
   "note": "crank stand, Ø5 shaft axis 40 mm up, Ø16 pocket for a 625 bearing (H7/m6), slotted feet 2 × M3 at 42 mm (print two; fits the gamma base plate slots)"
  },
  {
   "file": "crank-stand-625-h60",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-stand-625-h60.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-stand-625-h60.stl",
   "note": "crank stand, Ø5 shaft axis 60 mm up, Ø16 pocket for a 625 bearing (H7/m6), slotted feet 2 × M3 at 42 mm (print two; fits the gamma base plate slots)"
  },
  {
   "file": "crank-disc-b3-stroke10",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke10.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke10.stl",
   "note": "crank disc Ø30 for a Ø3 crankshaft (the crank head's 623 towers), pin at 5.0 mm (10 mm stroke), M3 grub"
  },
  {
   "file": "crank-disc-b3-stroke15",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke15.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke15.stl",
   "note": "crank disc Ø30 for a Ø3 crankshaft (the crank head's 623 towers), pin at 7.5 mm (15 mm stroke), M3 grub"
  },
  {
   "file": "crank-disc-b3-stroke20",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke20.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke20.stl",
   "note": "crank disc Ø30 for a Ø3 crankshaft (the crank head's 623 towers), pin at 10.0 mm (20 mm stroke), M3 grub"
  },
  {
   "file": "rhombic-frame-head-1.5in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/rhombic-frame-head-1.5in.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/rhombic-frame-head-1.5in.stl",
   "note": "1.5 in rhombic frame head: ISO 2852 cap face, pedestal, two uprights 24 mm apart with 2 × M3 at ±20 mm, 55 mm above the face, matching the rhombic gear frame plates' mounting holes; gear axes land 70 mm above the face"
  },
  {
   "file": "rhombic-frame-head-2in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/rhombic-frame-head-2in.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/rhombic-frame-head-2in.stl",
   "note": "2 in rhombic frame head: ISO 2852 cap face, pedestal, two uprights 24 mm apart with 2 × M3 at ±20 mm, 55 mm above the face, matching the rhombic gear frame plates' mounting holes; gear axes land 70 mm above the face"
  },
  {
   "file": "rhombic-frame-head-3in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/rhombic-frame-head-3in.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-linkage-fittings/rhombic-frame-head-3in.stl",
   "note": "3 in rhombic frame head: ISO 2852 cap face, pedestal, two uprights 24 mm apart with 2 × M3 at ±20 mm, 55 mm above the face, matching the rhombic gear frame plates' mounting holes; gear axes land 70 mm above the face"
  }
 ],
 "markdown": "https://xemstudio.com/objects/stirling-linkage-fittings/index.md"
}