{
 "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": "two-pin-crank-disc-90",
 "name": "Two-pin crank disc, pins 90° apart, 6 / 8 / 10 mm throw",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Drives & mechanisms",
 "year": null,
 "question": "What crank disc gives 90° phase for an alpha Stirling with parallel cylinders?",
 "tags": [
  "alpha",
  "crank disc",
  "phase",
  "two pin",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "90 degree crank disc",
  "two pin crank disc",
  "alpha stirling crank 90 degrees"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 3,
 "url": "https://xemstudio.com/objects/two-pin-crank-disc-90/",
 "sheet_txt": "https://xemstudio.com/objects/two-pin-crank-disc-90/sheet.txt",
 "sheet": {
  "basis": "Alpha phase 90°: two pins a quarter-turn apart for parallel or in-line cylinders",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Ø30 × 6 disc with a Ø5 bore (fit: slide), a Ø2.5 radial hole (M3 tap size) for a grub screw, and two Ø3 pin holes (fit: press) 90° apart at the same throw.",
   "Throws 6, 8 and 10 mm give strokes of 12, 16 and 20 mm; on a 10 mL syringe (Ø14.5) that is 1.65 mL per 10 mm of stroke.",
   "For parallel or in-line cylinders only. Cylinders in a 90° V share one pin instead (alpha V-twin crank disc)."
  ],
  "table": {
   "columns": [
    "file",
    "throw",
    "stroke",
    "disc",
    "bore",
    "pins"
   ],
   "rows": [
    [
     "crank-disc-2pin-90deg-e6",
     6,
     12,
     "Ø30 × 6",
     5,
     "2 × Ø3 at 90°"
    ],
    [
     "crank-disc-2pin-90deg-e8",
     8,
     16,
     "Ø30 × 6",
     5,
     "2 × Ø3 at 90°"
    ],
    [
     "crank-disc-2pin-90deg-e10",
     10,
     20,
     "Ø30 × 6",
     5,
     "2 × Ø3 at 90°"
    ]
   ]
  }
 },
 "sheet_text": "Two-pin crank disc, pins 90° apart, 6 / 8 / 10 mm throw — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/two-pin-crank-disc-90/  (CC BY 4.0)\nBasis: Alpha phase 90°: two pins a quarter-turn apart for parallel or in-line cylinders\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Ø30 × 6 disc with a Ø5 bore (fit: slide), a Ø2.5 radial hole (M3 tap size) for a grub screw, and two Ø3 pin holes (fit: press) 90° apart at the same throw.\n- Throws 6, 8 and 10 mm give strokes of 12, 16 and 20 mm; on a 10 mL syringe (Ø14.5) that is 1.65 mL per 10 mm of stroke.\n- For parallel or in-line cylinders only. Cylinders in a 90° V share one pin instead (alpha V-twin crank disc).\n\nfile  throw  stroke  disc  bore  pins\ncrank-disc-2pin-90deg-e6  6  12  Ø30 × 6  5  2 × Ø3 at 90°\ncrank-disc-2pin-90deg-e8  8  16  Ø30 × 6  5  2 × Ø3 at 90°\ncrank-disc-2pin-90deg-e10  10  20  Ø30 × 6  5  2 × Ø3 at 90°\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine\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, 3 parts): https://xemstudio.com/files/hardware/two-pin-crank-disc-90/index.json\nAPI: https://xemstudio.com/api/geometry?object=two-pin-crank-disc-90\n",
 "sources": [
  {
   "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",
   "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": [
  "alpha-v-twin-crank-disc",
  "transfer-tee-4mm",
  "ross-yoke",
  "pin-end-con-rods",
  "dowel-pins-metric"
 ],
 "fits": [
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "stirling-crankshafts",
     "why": "Ø5 shaft in the bore"
    },
    {
     "slug": "pin-end-con-rods",
     "why": "one con-rod per pin"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "alpha-v-twin-crank-disc",
     "why": "one-pin disc for a 90° V"
    },
    {
     "slug": "ross-yoke",
     "why": "parallel cylinders on a Ross yoke"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "dowel-pins-metric",
     "why": "Ø3 crank pins"
    }
   ]
  }
 ],
 "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": "disc bore",
   "exact": "Ø5",
   "mates": "Ø5 shaft (M3 grub)",
   "fit": "slide",
   "files": "crank-disc-"
  },
  {
   "feature": "disc pin holes",
   "exact": "Ø3",
   "mates": "Ø3 crank pins",
   "fit": "press",
   "files": "crank-disc-"
  },
  {
   "feature": "disc grub hole",
   "exact": "Ø2.5",
   "mates": "M3 tap drill",
   "fit": "designed",
   "files": "crank-disc-"
  }
 ],
 "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 phase angle does an alpha Stirling use?",
   "a": "90°: with parallel cylinders put the two pins a quarter-turn apart, as on this disc."
  },
  {
   "q": "Can I use the two-pin disc on a V-twin?",
   "a": "Not on a 90° V: it would give 0° or 180°. A 90° V uses one pin for both rods."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "crank-disc-2pin-90deg-e6",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/alpha-twin-crank-90/crank-disc-2pin-90deg-e6.step",
   "stl": "https://xemstudio.com/files/hardware/alpha-twin-crank-90/crank-disc-2pin-90deg-e6.stl",
   "note": "crank disc with two Ø3 pin holes 90° apart at 6 mm (stroke 12): for PARALLEL alpha cylinders (not a 90° V, which uses one pin)"
  },
  {
   "file": "crank-disc-2pin-90deg-e8",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/alpha-twin-crank-90/crank-disc-2pin-90deg-e8.step",
   "stl": "https://xemstudio.com/files/hardware/alpha-twin-crank-90/crank-disc-2pin-90deg-e8.stl",
   "note": "crank disc with two Ø3 pin holes 90° apart at 8 mm (stroke 16): for PARALLEL alpha cylinders (not a 90° V, which uses one pin)"
  },
  {
   "file": "crank-disc-2pin-90deg-e10",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/alpha-twin-crank-90/crank-disc-2pin-90deg-e10.step",
   "stl": "https://xemstudio.com/files/hardware/alpha-twin-crank-90/crank-disc-2pin-90deg-e10.stl",
   "note": "crank disc with two Ø3 pin holes 90° apart at 10 mm (stroke 20): for PARALLEL alpha cylinders (not a 90° V, which uses one pin)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/two-pin-crank-disc-90/index.md"
}