{
 "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": "rhombic-frame-head",
 "name": "Rhombic frame head for the 2 in tri-clamp beta: gear-shaft walls on a clamp-on cap",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Drives & mechanisms",
 "year": null,
 "question": "What holds the gears of a rhombic drive on a 2 inch tri-clamp spool?",
 "tags": [
  "rhombic",
  "frame",
  "tri-clamp",
  "beta",
  "stirling",
  "cap",
  "long earth society"
 ],
 "aliases": [
  "rhombic drive mount tri clamp",
  "rhombic drive frame",
  "beta stirling tri clamp head",
  "rhombic gear plate mount"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/rhombic-frame-head/",
 "sheet_txt": "https://xemstudio.com/objects/rhombic-frame-head/sheet.txt",
 "sheet": {
  "basis": "ISO 2852 cap face; 625 bearing (5 × 16 × 5) pockets on the rhombic gear centre distance 66; heights and planes from the rhombic kinematics in tools/rhombic_geom.py",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "An ISO 2852 cap face for the 2 in ferrule, a Ø50.8 pedestal clear of the clamp, and a 96 × 87 × 4 platform at 14 mm with a Ø24 rod window on the spool axis.",
   "Two walls, 5 mm thick and 96 wide, stand on the platform behind the spool axis (y -31..-26 and -61..-56); each has two Ø16 through pockets for 625 bearings (fit: press) at x ±33, 62 mm above the face: the two Ø5 gear shafts, 66 mm apart, the meshing distance of the module 1.5 × 44 T gears.",
   "The gears hang in front of the front wall on the shaft ends; links and yokes are in front of them on the rod axis. At 62 mm the gears, the lower links and the lower yoke all stay above the platform through a full turn.",
   "The rear wall's shaft collars and the 1 mm spacers between gear hubs and front bearings hold each shaft axially."
  ],
  "table": {
   "columns": [
    "feature",
    "size_mm",
    "position_mm"
   ],
   "rows": [
    [
     "ISO 2852 face",
     "2 in (Ø64 rim)",
     "z 0"
    ],
    [
     "platform",
     "96 × 87 × 4",
     "z 14..18"
    ],
    [
     "walls",
     "96 × 5, to z 75",
     "y -31..-26, -61..-56"
    ],
    [
     "625 pockets",
     "Ø16 through",
     "x ±33, z 62"
    ],
    [
     "rod window",
     "Ø24",
     "on the axis"
    ]
   ]
  }
 },
 "sheet_text": "Rhombic frame head for the 2 in tri-clamp beta: gear-shaft walls on a clamp-on cap — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/rhombic-frame-head/  (CC BY 4.0)\nBasis: ISO 2852 cap face; 625 bearing (5 × 16 × 5) pockets on the rhombic gear centre distance 66; heights and planes from the rhombic kinematics in tools/rhombic_geom.py\nCatalog version: 2026-10-20\n\nSizes: see table below\n- An ISO 2852 cap face for the 2 in ferrule, a Ø50.8 pedestal clear of the clamp, and a 96 × 87 × 4 platform at 14 mm with a Ø24 rod window on the spool axis.\n- Two walls, 5 mm thick and 96 wide, stand on the platform behind the spool axis (y -31..-26 and -61..-56); each has two Ø16 through pockets for 625 bearings (fit: press) at x ±33, 62 mm above the face: the two Ø5 gear shafts, 66 mm apart, the meshing distance of the module 1.5 × 44 T gears.\n- The gears hang in front of the front wall on the shaft ends; links and yokes are in front of them on the rod axis. At 62 mm the gears, the lower links and the lower yoke all stay above the platform through a full turn.\n- The rear wall's shaft collars and the 1 mm spacers between gear hubs and front bearings hold each shaft axially.\n\nfeature  size_mm  position_mm\nISO 2852 face  2 in (Ø64 rim)  z 0\nplatform  96 × 87 × 4  z 14..18\nwalls  96 × 5, to z 75  y -31..-26, -61..-56\n625 pockets  Ø16 through  x ±33, z 62\nrod window  Ø24  on the axis\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, 1 parts): https://xemstudio.com/files/hardware/rhombic-frame-head/index.json\nAPI: https://xemstudio.com/api/geometry?object=rhombic-frame-head\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": [
  "rhombic-crank-gear",
  "tri-clamp-spool",
  "tri-clamp-clamps",
  "list-beta-rhombic-2in"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "tri-clamp-spool",
     "why": "ISO 2852 face on the ferrule with a gasket"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "rhombic-crank-gear",
     "why": "gear shafts in the 625s, 66 apart"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "tri-clamp-clamps",
     "why": "clamp over the ferrule"
    },
    {
     "slug": "ball-bearings-metric",
     "why": "four 625s"
    }
   ]
  }
 ],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [
  {
   "feature": "rhombic head face",
   "exact": "ISO 2852",
   "mates": "ferrule face + Type B gasket",
   "fit": "clamp",
   "files": "rhombic-frame-head-"
  },
  {
   "feature": "rhombic head bearing pockets",
   "exact": "Ø16 through, 5",
   "mates": "625 bearing (gear shafts)",
   "fit": "press",
   "files": "rhombic-frame-head-"
  },
  {
   "feature": "rhombic head rod window",
   "exact": "Ø24",
   "mates": "tube rod, plug stub, lower yoke boss (no contact)",
   "fit": "designed",
   "files": "rhombic-frame-head-"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. Typical FDM: hole +0.0 to +0.1 mm on diameter.",
  "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. Typical FDM: +0.2 mm.",
  "run": "turns or slides in use: pin in a link, rod through a guide. Typical FDM: +0.3 mm.",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. Typical FDM: +0.3 mm.",
  "clamp": "split part that closes on the mating part with screws: make it at size.",
  "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change."
 },
 "faq": [
  {
   "q": "How does the rhombic drive attach to a tri-clamp spool?",
   "a": "The frame head clamps on the spool's open ferrule like any cap; its two walls carry the two gear shafts in 625 bearings, 66 mm apart and 62 mm above the face."
  },
  {
   "q": "Which bearings does the rhombic frame head take?",
   "a": "Four 625s (5 × 16 × 5), two per wall, flush in Ø16 through pockets."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "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, Ø50.8 pedestal to 14, 96 × 87 platform 14..18, two 5 mm walls (y -31..-26 and -61..-56 behind the spool axis) with Ø16 through pockets for 625 bearings at x ±33, 62 above the face; Ø24 rod window on the axis"
  }
 ],
 "markdown": "https://xemstudio.com/objects/rhombic-frame-head/index.md"
}