{
 "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": "gamma-base-plate-and-beam",
 "name": "Gamma frame: base plates for tri-clamp engines, rocker beam and pivot post",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Drives & mechanisms",
 "year": null,
 "question": "What frame do I need to mount a tri-clamp Stirling engine with its crank?",
 "tags": [
  "frame",
  "base plate",
  "beam",
  "rocker",
  "gamma",
  "stirling",
  "gamma",
  "long earth society"
 ],
 "aliases": [
  "stirling engine base plate",
  "beam engine stirling",
  "rocker beam stirling displacer",
  "tri clamp engine mount",
  "walking beam stirling"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 7,
 "url": "https://xemstudio.com/objects/gamma-base-plate-and-beam/",
 "sheet_txt": "https://xemstudio.com/objects/gamma-base-plate-and-beam/sheet.txt",
 "sheet": {
  "basis": "Base plate sized to the ISO 2852 flange of each spool size with slotted crank-stand mounts and the 2020 hole pattern; classic beam-driven gamma uses a rocker beam on a 623 pivot to drive the displacer from the crank",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Base plate: the spool (or its cap) sits in the bore; crank stands bolt into the slots so the crank height and rod alignment can be set; four M5 holes drop it onto 2020 extrusion or any bench. Print in PETG 6 mm, or use it as a drilling template for aluminium.",
   "Rocker beam: pivot in the middle on a 623 bearing on the post; one end to the crank con-rod, the other to the displacer rod. It converts the crank's motion to the displacer stroke with a lever ratio (set by where the pins sit) and lets the crank sit beside the engine instead of above it: the classic 'beam engine' gamma. Ratio 1:1 at the end holes; drill nearer the pivot for a shorter displacer stroke.",
   "Everything mounts on Ø3 pins and M3 screws; stands and heads from the other entries."
  ],
  "table": {
   "columns": [
    "part",
    "size",
    "fits"
   ],
   "rows": [
    [
     "base plate 1.5 in",
     "140 × 70 × 6",
     "50.5 flange"
    ],
    [
     "base plate 2 in",
     "154 × 70 × 6",
     "64 flange"
    ],
    [
     "base plate 3 in",
     "181 × 70 × 6",
     "91 flange"
    ],
    [
     "rocker beam",
     "60 / 80 / 100",
     "623 pivot, Ø3 ends"
    ],
    [
     "pivot post",
     "60 tall",
     "M3 foot"
    ]
   ]
  }
 },
 "sheet_text": "Gamma frame: base plates for tri-clamp engines, rocker beam and pivot post — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/gamma-base-plate-and-beam/  (CC BY 4.0)\nBasis: Base plate sized to the ISO 2852 flange of each spool size with slotted crank-stand mounts and the 2020 hole pattern; classic beam-driven gamma uses a rocker beam on a 623 pivot to drive the displacer from the crank\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Base plate: the spool (or its cap) sits in the bore; crank stands bolt into the slots so the crank height and rod alignment can be set; four M5 holes drop it onto 2020 extrusion or any bench. Print in PETG 6 mm, or use it as a drilling template for aluminium.\n- Rocker beam: pivot in the middle on a 623 bearing on the post; one end to the crank con-rod, the other to the displacer rod. It converts the crank's motion to the displacer stroke with a lever ratio (set by where the pins sit) and lets the crank sit beside the engine instead of above it: the classic 'beam engine' gamma. Ratio 1:1 at the end holes; drill nearer the pivot for a shorter displacer stroke.\n- Everything mounts on Ø3 pins and M3 screws; stands and heads from the other entries.\n\npart  size  fits\nbase plate 1.5 in  140 × 70 × 6  50.5 flange\nbase plate 2 in  154 × 70 × 6  64 flange\nbase plate 3 in  181 × 70 × 6  91 flange\nrocker beam  60 / 80 / 100  623 pivot, Ø3 ends\npivot post  60 tall  M3 foot\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Beam engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Beam_engine\n- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine\n- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 7 parts): https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/index.json\nAPI: https://xemstudio.com/api/geometry?object=gamma-base-plate-and-beam\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Beam engine",
   "url": "https://en.wikipedia.org/wiki/Beam_engine",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Stirling engine",
   "url": "https://en.wikipedia.org/wiki/Stirling_engine",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "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": [
  "t-slot-extrusions",
  "t-slot-brackets-and-nuts",
  "can-engine-printed-kit",
  "crank-conrod-flywheel-kit",
  "tri-clamp-displacers-and-heads"
 ],
 "fits": [
  {
   "role": "Parts that fit it",
   "items": [
    {
     "slug": "power-cylinder-piston-crosshead",
     "why": "liner on the base plate"
    }
   ]
  },
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "t-slot-extrusions",
     "why": "4 × M5 to 2020"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "stirling-linkage-fittings",
     "why": "625 crank stands in the slots"
    },
    {
     "slug": "tri-clamp-spool",
     "why": "spool bore"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "t-slot-brackets-and-nuts",
     "why": "T-nuts"
    }
   ]
  }
 ],
 "faq": [
  {
   "q": "How do I mount a tri-clamp Stirling engine?",
   "a": "Base plate with the spool bore and slotted crank-stand mounts; bolt it to 2020 extrusion with M5 button heads or to a board."
  },
  {
   "q": "What is a beam-driven Stirling engine?",
   "a": "The crank drives a rocker beam whose far end lifts the displacer: the crank can sit beside the cylinder and the beam's lever ratio sets the displacer stroke."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "base-plate-1.5in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/base-plate-1.5in.step",
   "stl": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/base-plate-1.5in.stl",
   "note": "base plate for a 1.5 in tri-clamp engine: spool bore, slotted crank-stand mounts, 4 × M5 to 2020 extrusion, 6 thick"
  },
  {
   "file": "base-plate-2in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/base-plate-2in.step",
   "stl": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/base-plate-2in.stl",
   "note": "base plate for a 2 in tri-clamp engine: spool bore, slotted crank-stand mounts, 4 × M5 to 2020 extrusion, 6 thick"
  },
  {
   "file": "base-plate-3in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/base-plate-3in.step",
   "stl": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/base-plate-3in.stl",
   "note": "base plate for a 3 in tri-clamp engine: spool bore, slotted crank-stand mounts, 4 × M5 to 2020 extrusion, 6 thick"
  },
  {
   "file": "rocker-beam-60",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-60.step",
   "stl": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-60.stl",
   "note": "rocker beam 60 mm, centre pivot on a 623, Ø3.2 ends (beam-driven displacer)"
  },
  {
   "file": "rocker-beam-80",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-80.step",
   "stl": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-80.stl",
   "note": "rocker beam 80 mm, centre pivot on a 623, Ø3.2 ends (beam-driven displacer)"
  },
  {
   "file": "rocker-beam-100",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-100.step",
   "stl": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-100.stl",
   "note": "rocker beam 100 mm, centre pivot on a 623, Ø3.2 ends (beam-driven displacer)"
  },
  {
   "file": "pivot-post-60",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/pivot-post-60.step",
   "stl": "https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/pivot-post-60.stl",
   "note": "beam pivot post 60 mm, Ø3 pin, 2 × M3 foot"
  }
 ],
 "markdown": "https://xemstudio.com/objects/gamma-base-plate-and-beam/index.md"
}