{
 "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": "connecting-rods-623",
 "name": "Connecting rods 30 to 80 mm centres with 623 pockets",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Drives & mechanisms",
 "year": null,
 "question": "What does a model engine connecting rod with 623 bearings look like?",
 "tags": [
  "connecting rod",
  "con-rod",
  "623",
  "crank",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "connecting rod 3d model",
  "con rod 623 bearing",
  "model engine connecting rod",
  "conrod stl"
 ],
 "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/connecting-rods-623/",
 "sheet_txt": "https://xemstudio.com/objects/connecting-rods-623/sheet.txt",
 "sheet": {
  "basis": "Flat rod 5 thick, Ø14 ends with Ø10 pockets (623 OD) at the stated centres",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A flat rod 5 thick: an 8 mm wide web between two Ø14 bosses, each with a Ø10 pocket through for a 623 (3 × 10 × 4).",
   "Centres 30, 40, 50, 60 and 80 mm; overall length centres + 14.",
   "Both ends run on Ø3 pins. A rod at least twice the stroke keeps the piston side load low; the 2 in engines pair conrod-50 with a 20 mm stroke."
  ],
  "table": {
   "columns": [
    "file",
    "centres",
    "overall",
    "thickness",
    "pockets"
   ],
   "rows": [
    [
     "conrod-30",
     30,
     44,
     5,
     "2 × Ø10"
    ],
    [
     "conrod-40",
     40,
     54,
     5,
     "2 × Ø10"
    ],
    [
     "conrod-50",
     50,
     64,
     5,
     "2 × Ø10"
    ],
    [
     "conrod-60",
     60,
     74,
     5,
     "2 × Ø10"
    ],
    [
     "conrod-80",
     80,
     94,
     5,
     "2 × Ø10"
    ]
   ]
  }
 },
 "sheet_text": "Connecting rods 30 to 80 mm centres with 623 pockets — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/connecting-rods-623/  (CC BY 4.0)\nBasis: Flat rod 5 thick, Ø14 ends with Ø10 pockets (623 OD) at the stated centres\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A flat rod 5 thick: an 8 mm wide web between two Ø14 bosses, each with a Ø10 pocket through for a 623 (3 × 10 × 4).\n- Centres 30, 40, 50, 60 and 80 mm; overall length centres + 14.\n- Both ends run on Ø3 pins. A rod at least twice the stroke keeps the piston side load low; the 2 in engines pair conrod-50 with a 20 mm stroke.\n\nfile  centres  overall  thickness  pockets\nconrod-30  30  44  5  2 × Ø10\nconrod-40  40  54  5  2 × Ø10\nconrod-50  50  64  5  2 × Ø10\nconrod-60  60  74  5  2 × Ø10\nconrod-80  80  94  5  2 × Ø10\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Crank (mechanism) — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Crank_(mechanism)\n- Wikipedia: Flywheel — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Flywheel\n- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine\n- Long Earth Society: Engine builds that use these parts (videos and write-ups) — 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/connecting-rods-623/index.json\nAPI: https://xemstudio.com/api/geometry?object=connecting-rods-623\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Crank (mechanism)",
   "url": "https://en.wikipedia.org/wiki/Crank_(mechanism)",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Flywheel",
   "url": "https://en.wikipedia.org/wiki/Flywheel",
   "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 that use these parts (videos and write-ups)",
   "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": [
  "crank-discs-5mm-bore",
  "rod-clevises",
  "pins-3mm",
  "ball-bearings-metric",
  "power-cylinder-liner"
 ],
 "fits": [
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "crank-discs-5mm-bore",
     "why": "623 on the Ø3 crank pin"
    },
    {
     "slug": "rod-clevises",
     "why": "5 mm rod end in the 5 mm gap"
    },
    {
     "slug": "tri-clamp-power-piston",
     "why": "wrist-pin end"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "ball-bearings-metric",
     "why": "623 in each Ø10 pocket"
    }
   ]
  }
 ],
 "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": "con-rod bearing pockets",
   "exact": "Ø10",
   "mates": "623 bearing",
   "fit": "press",
   "files": "conrod-"
  }
 ],
 "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 bearings go in the connecting rod?",
   "a": "A 623 (3 × 10 × 4) in each Ø10 pocket, on Ø3 pins."
  },
  {
   "q": "How long a con-rod for a 20 mm stroke?",
   "a": "At least 40 mm centres; the 2 in tri-clamp engines run 50."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "conrod-30",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-30.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-30.stl",
   "note": "connecting rod, 30 mm centres, Ø10 pockets for 623 bearings both ends, 5 thick"
  },
  {
   "file": "conrod-40",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-40.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-40.stl",
   "note": "connecting rod, 40 mm centres, Ø10 pockets for 623 bearings both ends, 5 thick"
  },
  {
   "file": "conrod-50",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-50.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-50.stl",
   "note": "connecting rod, 50 mm centres, Ø10 pockets for 623 bearings both ends, 5 thick"
  },
  {
   "file": "conrod-60",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-60.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-60.stl",
   "note": "connecting rod, 60 mm centres, Ø10 pockets for 623 bearings both ends, 5 thick"
  },
  {
   "file": "conrod-80",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-80.step",
   "stl": "https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-80.stl",
   "note": "connecting rod, 80 mm centres, Ø10 pockets for 623 bearings both ends, 5 thick"
  }
 ],
 "markdown": "https://xemstudio.com/objects/connecting-rods-623/index.md"
}