{
 "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": "flexure-rim-clamp-plate",
 "name": "Flexure rim clamp plate: Ø40 to Ø120 × 3 mm, 3 × M3",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Free-piston",
 "year": null,
 "question": "What clamps the rims of a flexure bearing stack?",
 "tags": [
  "flexure",
  "clamp plate",
  "free piston",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "flexure clamp plate",
  "flexure rim clamp",
  "flexure stack clamp ring"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 5,
 "url": "https://xemstudio.com/objects/flexure-rim-clamp-plate/",
 "sheet_txt": "https://xemstudio.com/objects/flexure-rim-clamp-plate/sheet.txt",
 "sheet": {
  "basis": "Ring = the flexure rim (OD, width 0.12 OD), 3 mm thick, 3 × Ø3.4 on the 0.88 × OD circle",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A 3 mm ring the size of the leaf rim with three Ø3.4 holes on the rim-hole circle: it clamps the stack of leaf rims and spacers down to the head.",
   "Ø40 to Ø120; hole circles Ø35.2 / 52.8 / 70.4 / 88 / 105.6, matching the leaves and the tri-clamp flexure head."
  ],
  "table": {
   "columns": [
    "od_mm",
    "width_mm",
    "thickness_mm",
    "holes",
    "hole_circle_mm"
   ],
   "rows": [
    [
     40,
     4.8,
     3,
     "3 × Ø3.4",
     35.2
    ],
    [
     60,
     7.2,
     3,
     "3 × Ø3.4",
     52.8
    ],
    [
     80,
     9.6,
     3,
     "3 × Ø3.4",
     70.4
    ],
    [
     100,
     12,
     3,
     "3 × Ø3.4",
     88
    ],
    [
     120,
     14.4,
     3,
     "3 × Ø3.4",
     105.6
    ]
   ]
  }
 },
 "sheet_text": "Flexure rim clamp plate: Ø40 to Ø120 × 3 mm, 3 × M3 — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/flexure-rim-clamp-plate/  (CC BY 4.0)\nBasis: Ring = the flexure rim (OD, width 0.12 OD), 3 mm thick, 3 × Ø3.4 on the 0.88 × OD circle\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A 3 mm ring the size of the leaf rim with three Ø3.4 holes on the rim-hole circle: it clamps the stack of leaf rims and spacers down to the head.\n- Ø40 to Ø120; hole circles Ø35.2 / 52.8 / 70.4 / 88 / 105.6, matching the leaves and the tri-clamp flexure head.\n\nod_mm  width_mm  thickness_mm  holes  hole_circle_mm\n40  4.8  3  3 × Ø3.4  35.2\n60  7.2  3  3 × Ø3.4  52.8\n80  9.6  3  3 × Ø3.4  70.4\n100  12  3  3 × Ø3.4  88.0\n120  14.4  3  3 × Ø3.4  105.6\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- NASA (NTRS, public domain): Free-piston Stirling convertor flexure bearing development and life testing (2005) — PDF — US Government work, public domain — https://ntrs.nasa.gov/search?q=20050182933\n- NASA (NTRS, public domain): Flexure bearing design for free-piston Stirling engines (1986) — PDF — US Government work, public domain — https://ntrs.nasa.gov/search?q=19860020334\n- NASA (NTRS, public domain): Advanced Stirling Radioisotope Generator (ASRG) engineering unit (2011) — PDF — US Government work, public domain — https://ntrs.nasa.gov/search?q=20110016393\n- Wikipedia: Flexure bearing — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Flexure_bearing\n- Sunpower (AMETEK): Free-piston Stirling technology overview — web — Sunpower site [verify license at link] — https://sunpowerinc.com/\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, 5 parts): https://xemstudio.com/files/hardware/flexure-rim-clamp-plate/index.json\nAPI: https://xemstudio.com/api/geometry?object=flexure-rim-clamp-plate\n",
 "sources": [
  {
   "publisher": "NASA (NTRS, public domain)",
   "title": "Free-piston Stirling convertor flexure bearing development and life testing (2005)",
   "url": "https://ntrs.nasa.gov/search?q=20050182933",
   "formats": [
    "PDF"
   ],
   "license": "US Government work, public domain",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "NASA (NTRS, public domain)",
   "title": "Flexure bearing design for free-piston Stirling engines (1986)",
   "url": "https://ntrs.nasa.gov/search?q=19860020334",
   "formats": [
    "PDF"
   ],
   "license": "US Government work, public domain",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "NASA (NTRS, public domain)",
   "title": "Advanced Stirling Radioisotope Generator (ASRG) engineering unit (2011)",
   "url": "https://ntrs.nasa.gov/search?q=20110016393",
   "formats": [
    "PDF"
   ],
   "license": "US Government work, public domain",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Flexure bearing",
   "url": "https://en.wikipedia.org/wiki/Flexure_bearing",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Sunpower (AMETEK)",
   "title": "Free-piston Stirling technology overview",
   "url": "https://sunpowerinc.com/",
   "formats": [
    "web"
   ],
   "license": "Sunpower site",
   "license_verified": false,
   "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": [
  "spiral-flexure-bearing",
  "flexure-stack-spacer",
  "tri-clamp-flexure-head",
  "socket-head-cap-screws-metric"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "spiral-flexure-bearing",
     "why": "on top of the leaf rims"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "tri-clamp-flexure-head",
     "why": "same three-hole circle"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "socket-head-cap-screws-metric",
     "why": "3 × M3"
    }
   ]
  }
 ],
 "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": "clamp-plate holes",
   "exact": "Ø3.4",
   "mates": "M3 screw clearance",
   "fit": "designed",
   "files": "clamp-plate-"
  }
 ],
 "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": "What screws hold the flexure clamp plate?",
   "a": "Three M3 through Ø3.4 holes on the rim circle (Ø70.4 for the Ø80 plate)."
  },
  {
   "q": "How thick is the clamp plate?",
   "a": "3 mm."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "clamp-plate-40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/spiral-flexure-bearings/clamp-plate-40.step",
   "stl": "https://xemstudio.com/files/hardware/spiral-flexure-bearings/clamp-plate-40.stl",
   "note": "rim clamp plate Ø40, 3 thick, 3 × Ø3.4 (M3) on R17.6"
  },
  {
   "file": "clamp-plate-60",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/spiral-flexure-bearings/clamp-plate-60.step",
   "stl": "https://xemstudio.com/files/hardware/spiral-flexure-bearings/clamp-plate-60.stl",
   "note": "rim clamp plate Ø60, 3 thick, 3 × Ø3.4 (M3) on R26.4"
  },
  {
   "file": "clamp-plate-80",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/spiral-flexure-bearings/clamp-plate-80.step",
   "stl": "https://xemstudio.com/files/hardware/spiral-flexure-bearings/clamp-plate-80.stl",
   "note": "rim clamp plate Ø80, 3 thick, 3 × Ø3.4 (M3) on R35.2"
  },
  {
   "file": "clamp-plate-100",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/spiral-flexure-bearings/clamp-plate-100.step",
   "stl": "https://xemstudio.com/files/hardware/spiral-flexure-bearings/clamp-plate-100.stl",
   "note": "rim clamp plate Ø100, 3 thick, 3 × Ø3.4 (M3) on R44"
  },
  {
   "file": "clamp-plate-120",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/spiral-flexure-bearings/clamp-plate-120.step",
   "stl": "https://xemstudio.com/files/hardware/spiral-flexure-bearings/clamp-plate-120.stl",
   "note": "rim clamp plate Ø120, 3 thick, 3 × Ø3.4 (M3) on R52.8"
  }
 ],
 "markdown": "https://xemstudio.com/objects/flexure-rim-clamp-plate/index.md"
}