{
 "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": "htd-crank-linkage",
 "name": "HTD crank and linkage: webs, link web, con-rods, clevis and Ø12 shafts for a 3 in cross crankcase",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Tri-clamp engine parts",
 "year": null,
 "question": "How is the crank of the 10 in HTD engine laid out?",
 "tags": [
  "htd",
  "crank",
  "crankshaft",
  "con-rod",
  "stirling"
 ],
 "aliases": [
  "stirling built up crank",
  "gamma stirling crank 90 degrees",
  "tri clamp cross crankcase crank"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 8,
 "url": "https://xemstudio.com/objects/htd-crank-linkage/",
 "sheet_txt": "https://xemstudio.com/objects/htd-crank-linkage/sheet.txt",
 "sheet": {
  "basis": "Exact geometry; designed running gaps between every moving plane",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Built-up crank on Ø12 shafts in 6001 bearings: web A (displacer throw r 4) – Ø5 pin through the displacer con-rod's 625 – link web – Ø5 pin through the piston con-rod's 625 – web C (piston throw r 20). The displacer pin leads the piston pin by 90°.",
   "Planes along the shaft (x): web A disc −9.5..−3.5, displacer con-rod −2.5..2.5, link web 3.5..9.5, piston con-rod 10.5..15.5, web C 16.5..22.5: 1.0 between every rod and web (designed). Pins are Ø5 × 16 dowels pressed in the webs.",
   "Con-rods 60 (displacer, to the clevis on the rod) and 237 (piston, down through the reducer to the piston's cheeks); every eye runs on a 625. Sweep radius 31 (piston eye) inside the 3 in cross bore Ø72.9."
  ],
  "table": {
   "columns": [
    "part",
    "role",
    "size"
   ],
   "rows": [
    [
     "crank-web-r8-b12",
     "displacer web",
     "r 4"
    ],
    [
     "crank-web-link-r8-r20",
     "link web",
     "r 4 / 20"
    ],
    [
     "crank-web-r20-b12",
     "piston web",
     "r 20"
    ],
    [
     "conrod-60-625",
     "con-rod",
     60
    ],
    [
     "conrod-237-625",
     "con-rod",
     237
    ],
    [
     "rod-clevis-6-pin5",
     "rod clevis",
     "Ø6 rod, Ø5 pin"
    ],
    [
     "shaft-12x76",
     "shaft",
     76
    ],
    [
     "shaft-12x210",
     "shaft",
     210
    ]
   ]
  }
 },
 "sheet_text": "HTD crank and linkage: webs, link web, con-rods, clevis and Ø12 shafts for a 3 in cross crankcase — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/htd-crank-linkage/  (CC BY 4.0)\nBasis: Exact geometry; designed running gaps between every moving plane\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Built-up crank on Ø12 shafts in 6001 bearings: web A (displacer throw r 4) – Ø5 pin through the displacer con-rod's 625 – link web – Ø5 pin through the piston con-rod's 625 – web C (piston throw r 20). The displacer pin leads the piston pin by 90°.\n- Planes along the shaft (x): web A disc −9.5..−3.5, displacer con-rod −2.5..2.5, link web 3.5..9.5, piston con-rod 10.5..15.5, web C 16.5..22.5: 1.0 between every rod and web (designed). Pins are Ø5 × 16 dowels pressed in the webs.\n- Con-rods 60 (displacer, to the clevis on the rod) and 237 (piston, down through the reducer to the piston's cheeks); every eye runs on a 625. Sweep radius 31 (piston eye) inside the 3 in cross bore Ø72.9.\n\npart  role  size\ncrank-web-r8-b12  displacer web  r 4\ncrank-web-link-r8-r20  link web  r 4 / 20\ncrank-web-r20-b12  piston web  r 20\nconrod-60-625  con-rod  60.0\nconrod-237-625  con-rod  237.0\nrod-clevis-6-pin5  rod clevis  Ø6 rod, Ø5 pin\nshaft-12x76  shaft  76\nshaft-12x210  shaft  210\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\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, 8 parts): https://xemstudio.com/files/hardware/htd-crank-linkage/index.json\nAPI: https://xemstudio.com/api/geometry?object=htd-crank-linkage\n",
 "sources": [
  {
   "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": [
  "list-htd-10in",
  "htd-crankcase-caps-3in",
  "htd-power-pistons",
  "dowel-pins-metric",
  "ball-bearings-metric"
 ],
 "fits": [],
 "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": "web and hub bores",
   "exact": "Ø12",
   "mates": "Ø12 shafts (M4 grub on each hub)",
   "fit": "slide",
   "files": "crank-web-"
  },
  {
   "feature": "pin bores",
   "exact": "Ø5",
   "mates": "dowel-5x16 crank pins",
   "fit": "press",
   "files": "crank-web-"
  },
  {
   "feature": "con-rod pockets",
   "exact": "Ø16 × 5",
   "mates": "bearing-625 outer ring",
   "fit": "press",
   "files": "conrod-"
  },
  {
   "feature": "clevis socket",
   "exact": "Ø6 × 14",
   "mates": "displacer rod, M4 grub",
   "fit": "slide",
   "files": "rod-clevis-"
  },
  {
   "feature": "clevis slot and pin",
   "exact": "6.0 wide, Ø5",
   "mates": "5 thick con-rod; dowel-5x16",
   "fit": "press",
   "files": "rod-clevis-"
  },
  {
   "feature": "plane gaps",
   "exact": "1.0 between every web and con-rod plane",
   "mates": "neighbouring webs and rods",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "shafts",
   "exact": "Ø12",
   "mates": "bearing-6001 inner rings",
   "fit": "press",
   "files": "shaft-"
  }
 ],
 "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": "Why a built-up crank?",
   "a": "One-piece con-rod eyes on 625 bearings slide onto the pins before the webs close up; nothing has to be split."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "crank-web-r8-b12",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/htd-crank-linkage/crank-web-r8-b12.step",
   "stl": "https://xemstudio.com/files/hardware/htd-crank-linkage/crank-web-r8-b12.stl",
   "note": "crank web, hub type: disc R12 × 6 with a Ø5 pin at r 4 (8 displacer stroke), hub Ø24 × 8, Ø12 bore in the hub only, M4 tapped radial hole"
  },
  {
   "file": "crank-web-link-r8-r20",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/htd-crank-linkage/crank-web-link-r8-r20.step",
   "stl": "https://xemstudio.com/files/hardware/htd-crank-linkage/crank-web-link-r8-r20.stl",
   "note": "link web 6 thick: Ø5 displacer pin at r 4 and Ø5 piston pin at r 20, 90° apart"
  },
  {
   "file": "crank-web-r20-b12",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/htd-crank-linkage/crank-web-r20-b12.step",
   "stl": "https://xemstudio.com/files/hardware/htd-crank-linkage/crank-web-r20-b12.stl",
   "note": "crank web, hub type: disc R28 × 6 with a Ø5 pin at r 20 (40 piston stroke), hub Ø24 × 8, Ø12 bore through, M4 tapped radial hole"
  },
  {
   "file": "conrod-60-625",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/htd-crank-linkage/conrod-60-625.step",
   "stl": "https://xemstudio.com/files/hardware/htd-crank-linkage/conrod-60-625.stl",
   "note": "con-rod 60 centres, 5 thick, Ø16 pockets for 625 bearings, eyes Ø22"
  },
  {
   "file": "conrod-237-625",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/htd-crank-linkage/conrod-237-625.step",
   "stl": "https://xemstudio.com/files/hardware/htd-crank-linkage/conrod-237-625.stl",
   "note": "con-rod 237 centres, 5 thick, Ø16 pockets for 625 bearings, eyes Ø22"
  },
  {
   "file": "rod-clevis-6-pin5",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/htd-crank-linkage/rod-clevis-6-pin5.step",
   "stl": "https://xemstudio.com/files/hardware/htd-crank-linkage/rod-clevis-6-pin5.stl",
   "note": "rod clevis: 13 × 14 × 41 block, slot 6 wide for a 5 con-rod, Ø5 pin bore, Ø6 rod socket 14 deep, M4 tapped radial hole"
  },
  {
   "file": "shaft-12x76",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/htd-crank-linkage/shaft-12x76.step",
   "stl": "https://xemstudio.com/files/hardware/htd-crank-linkage/shaft-12x76.stl",
   "note": "Ø12 × 76 crankshaft, −X (main): blind-cap 6001 to web A's hub"
  },
  {
   "file": "shaft-12x210",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/htd-crank-linkage/shaft-12x210.step",
   "stl": "https://xemstudio.com/files/hardware/htd-crank-linkage/shaft-12x210.stl",
   "note": "Ø12 × 210 crankshaft, +X: web C, two 6001, the seal, gear and flywheel"
  }
 ],
 "markdown": "https://xemstudio.com/objects/htd-crank-linkage/index.md"
}