{
 "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": "alpha-twin-crank-90",
 "name": "Alpha V-twin: 90° two-pin crank discs, V block, transfer tee",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Drives & mechanisms",
 "year": null,
 "question": "How do I set the 90 degree phase on an alpha Stirling engine?",
 "tags": [
  "alpha",
  "v-twin",
  "crank",
  "phase",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "alpha stirling engine design",
  "alpha stirling 90 degree phase",
  "v twin stirling",
  "alpha stirling syringe",
  "two cylinder stirling"
 ],
 "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/alpha-twin-crank-90/",
 "sheet_txt": "https://xemstudio.com/objects/alpha-twin-crank-90/sheet.txt",
 "sheet": {
  "basis": "Alpha configuration: two pistons in separate hot and cold cylinders, 90° apart in phase; here with one crank disc carrying both pins 90° apart (V-twin) or two discs clocked on one shaft",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Alpha phase: the cold piston follows the hot piston by 90°. Simplest way: one crank disc with two pins 90° apart, cylinders in a 90° V over it (V-twin); both con-rods ride the same disc, each pin at the same throw e. Or two separate crank discs on one shaft, clocked 90° with set screws.",
   "V block: two 10 mL syringe barrels at 90° over the shaft; the hot barrel is glass if you have it (a plastic syringe survives a tea-light hot end at 80 °C only with the heat going into a copper tube, not the barrel). Transfer tee: 4 mm bores, hot → regenerator → cold.",
   "Strokes 12–20 mm (e 6–10) suit 10 mL syringes (Ø14.5: 1.65 mL per 10 mm). Alpha engines have the highest specific power of the three but need the piston seal on the hot side; the Ross yoke kit is the parallel-cylinder alternative."
  ],
  "table": {
   "columns": [
    "part",
    "size",
    "note"
   ],
   "rows": [
    [
     "crank disc 2-pin",
     "e 6 / 8 / 10",
     "pins 90° apart"
    ],
    [
     "V block",
     "2 × Ø16.05 @ 90°",
     "10 mL syringes"
    ],
    [
     "transfer tee",
     "4 mm",
     "regenerator between"
    ]
   ]
  }
 },
 "sheet_text": "Alpha V-twin: 90° two-pin crank discs, V block, transfer tee — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/alpha-twin-crank-90/  (CC BY 4.0)\nBasis: Alpha configuration: two pistons in separate hot and cold cylinders, 90° apart in phase; here with one crank disc carrying both pins 90° apart (V-twin) or two discs clocked on one shaft\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Alpha phase: the cold piston follows the hot piston by 90°. Simplest way: one crank disc with two pins 90° apart, cylinders in a 90° V over it (V-twin); both con-rods ride the same disc, each pin at the same throw e. Or two separate crank discs on one shaft, clocked 90° with set screws.\n- V block: two 10 mL syringe barrels at 90° over the shaft; the hot barrel is glass if you have it (a plastic syringe survives a tea-light hot end at 80 °C only with the heat going into a copper tube, not the barrel). Transfer tee: 4 mm bores, hot → regenerator → cold.\n- Strokes 12–20 mm (e 6–10) suit 10 mL syringes (Ø14.5: 1.65 mL per 10 mm). Alpha engines have the highest specific power of the three but need the piston seal on the hot side; the Ross yoke kit is the parallel-cylinder alternative.\n\npart  size  note\ncrank disc 2-pin  e 6 / 8 / 10  pins 90° apart\nV block  2 × Ø16.05 @ 90°  10 mL syringes\ntransfer tee  4 mm  regenerator between\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, 5 parts): https://xemstudio.com/files/hardware/alpha-twin-crank-90/index.json\nAPI: https://xemstudio.com/api/geometry?object=alpha-twin-crank-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": [
  "ross-yoke-kit",
  "crank-conrod-flywheel-kit",
  "plastic-syringes",
  "regenerator-and-heat-materials",
  "stirling-configurations-guide"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "plastic-syringes",
     "why": "10 mL barrels in the V-block"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "syringe-pistons",
     "why": "con-rods into the piston forks"
    },
    {
     "slug": "crank-conrod-flywheel-kit",
     "why": "con-rods and flywheel"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "ross-yoke-kit",
     "why": "parallel cylinders"
    },
    {
     "slug": "tri-clamp-power-pistons",
     "why": "two tri-clamp cups as the cylinders"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "dowel-pins-metric",
     "why": "Ø3 crank pin"
    }
   ]
  }
 ],
 "faq": [
  {
   "q": "What phase angle does an alpha Stirling use?",
   "a": "90°: the cold piston lags the hot piston by a quarter turn. One disc with two pins 90° apart (and cylinders in a 90° V) gives it automatically."
  },
  {
   "q": "Which alpha cylinder gets the heat?",
   "a": "The one whose piston leads: expansion space hot, compression space cold; gas flows through the regenerator between them."
  }
 ],
 "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": "single crank disc with two Ø3 pin holes 90° apart at 6 mm (stroke 12): both alpha con-rods on one disc"
  },
  {
   "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": "single crank disc with two Ø3 pin holes 90° apart at 8 mm (stroke 16): both alpha con-rods on one disc"
  },
  {
   "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": "single crank disc with two Ø3 pin holes 90° apart at 10 mm (stroke 20): both alpha con-rods on one disc"
  },
  {
   "file": "v-block-90-2x-syringe-10ml",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/alpha-twin-crank-90/v-block-90-2x-syringe-10ml.step",
   "stl": "https://xemstudio.com/files/hardware/alpha-twin-crank-90/v-block-90-2x-syringe-10ml.stl",
   "note": "90° V block for two 10 mL syringe barrels over one crank (alpha V-twin): bores meet 12 mm above the base"
  },
  {
   "file": "transfer-tee-4mm",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/alpha-twin-crank-90/transfer-tee-4mm.step",
   "stl": "https://xemstudio.com/files/hardware/alpha-twin-crank-90/transfer-tee-4mm.stl",
   "note": "4 mm transfer tee (hot cylinder → regenerator → cold cylinder)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/alpha-twin-crank-90/index.md"
}