{
 "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": "tri-clamp-cross-crank-webs",
 "name": "Inner crank webs for the tri-clamp cross gamma: two throws 90° apart on a Ø3 shaft",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "How do I make a two-throw crank at 90° that fits inside a 2 inch tri-clamp cross?",
 "tags": [
  "crank",
  "crank web",
  "two throw",
  "90 degree",
  "gamma",
  "tri-clamp",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "two throw crank 90 degrees",
  "built up crank stirling",
  "inner crank tri clamp",
  "crank inside crankcase stirling"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 2,
 "url": "https://xemstudio.com/objects/tri-clamp-cross-crank-webs/",
 "sheet_txt": "https://xemstudio.com/objects/tri-clamp-cross-crank-webs/sheet.txt",
 "sheet": {
  "basis": "Design values: 6 mm throws (12 mm strokes), Ø3 pins and shaft, 623 con-rod eyes (R7)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A built-up crank small enough to turn inside a Ø29 chamber in the middle of the cross. The hub web goes on the end of the Ø3 shaft (M3 grub); a Ø3 × 12 dowel pressed through its disc is the diaphragm crank pin; the con-rod for the diaphragm turns on it; the link web is pressed on the pin's far end.",
   "The link web carries the displacer pin, a second Ø3 × 12 dowel, 90° on from the diaphragm pin. Each pin passes only through its own con-rod: the shaft stops in the hub web, the diaphragm pin stops in the link web, the displacer pin starts there, so no con-rod eye ever meets another pin.",
   "Both throws are 6 mm. The con-rod eyes sweep a radius of 13; the webs are Ø20."
  ],
  "table": {
   "columns": [
    "file",
    "hub_mm",
    "disc_mm",
    "pins"
   ],
   "rows": [
    [
     "inner-crank-web-hub-r6",
     "Ø10 × 6, Ø3 bore, M3 grub",
     "Ø20 × 4",
     "1 at r 6"
    ],
    [
     "inner-crank-web-link-r6",
     "",
     "Ø20 × 5.5",
     "2 at r 6, 90° apart"
    ]
   ]
  }
 },
 "sheet_text": "Inner crank webs for the tri-clamp cross gamma: two throws 90° apart on a Ø3 shaft — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/tri-clamp-cross-crank-webs/  (CC BY 4.0)\nBasis: Design values: 6 mm throws (12 mm strokes), Ø3 pins and shaft, 623 con-rod eyes (R7)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A built-up crank small enough to turn inside a Ø29 chamber in the middle of the cross. The hub web goes on the end of the Ø3 shaft (M3 grub); a Ø3 × 12 dowel pressed through its disc is the diaphragm crank pin; the con-rod for the diaphragm turns on it; the link web is pressed on the pin's far end.\n- The link web carries the displacer pin, a second Ø3 × 12 dowel, 90° on from the diaphragm pin. Each pin passes only through its own con-rod: the shaft stops in the hub web, the diaphragm pin stops in the link web, the displacer pin starts there, so no con-rod eye ever meets another pin.\n- Both throws are 6 mm. The con-rod eyes sweep a radius of 13; the webs are Ø20.\n\nfile  hub_mm  disc_mm  pins\ninner-crank-web-hub-r6  Ø10 × 6, Ø3 bore, M3 grub  Ø20 × 4  1 at r 6\ninner-crank-web-link-r6    Ø20 × 5.5  2 at r 6, 90° apart\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, 2 parts): https://xemstudio.com/files/hardware/tri-clamp-cross-crank-webs/index.json\nAPI: https://xemstudio.com/api/geometry?object=tri-clamp-cross-crank-webs\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": [
  "tri-clamp-bearing-cap",
  "tri-clamp-cross-crankcase-insert",
  "connecting-rods-623",
  "dowel-pins-metric",
  "list-tri-clamp-cross-diaphragm-gamma"
 ],
 "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": "shaft bore",
   "exact": "Ø3",
   "mates": "Ø3 crankshaft (M3 grub)",
   "fit": "slide",
   "files": "inner-crank-web-hub-"
  },
  {
   "feature": "grub hole",
   "exact": "Ø2.5 (M3 tapped)",
   "mates": "set-m3x3",
   "fit": "designed",
   "files": "inner-crank-web-hub-"
  },
  {
   "feature": "crank-pin holes",
   "exact": "Ø3 at r 6 (link web: two, 90° apart)",
   "mates": "dowel-3x12 crank pins",
   "fit": "press",
   "files": "all"
  },
  {
   "feature": "throw",
   "exact": "6 (12 mm strokes), displacer pin 90° on",
   "mates": "conrod-30 eyes (623)",
   "fit": "designed",
   "files": "all"
  }
 ],
 "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": "Which way does it turn?",
   "a": "So that the displacer pin is a quarter turn ahead of the diaphragm pin: the build list states the direction."
  },
  {
   "q": "How is the link web held?",
   "a": "Pressed on the diaphragm pin, which is pressed in the hub web; the displacer pin is pressed in the link web."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "inner-crank-web-hub-r6",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-cross-crank-webs/inner-crank-web-hub-r6.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-cross-crank-webs/inner-crank-web-hub-r6.stl",
   "note": "hub web: Ø10 × 6 hub with Ø3 shaft bore and M3 grub hole (Ø2.5), Ø20 × 4 disc with the Ø3 crank-pin hole at r 6"
  },
  {
   "file": "inner-crank-web-link-r6",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-cross-crank-webs/inner-crank-web-link-r6.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-cross-crank-webs/inner-crank-web-link-r6.stl",
   "note": "link web: Ø20 × 5.5 disc, Ø3 pin holes at r 6, 90° apart"
  }
 ],
 "markdown": "https://xemstudio.com/objects/tri-clamp-cross-crank-webs/index.md"
}