{
 "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": "stirling-precision-rods",
 "name": "Ground rods, hollow piston rod and crank shafts for the performance engines (Ø6, Ø8, Ø10 / 7)",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "What rods and shafts does a tri-clamp crosshead Stirling engine need?",
 "tags": [
  "rod",
  "shaft",
  "piston rod",
  "tri-clamp",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "stirling rod lengths",
  "hollow piston rod"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 13,
 "url": "https://xemstudio.com/objects/stirling-precision-rods/",
 "sheet_txt": "https://xemstudio.com/objects/stirling-precision-rods/sheet.txt",
 "sheet": {
  "basis": "Design values; lengths from the engines' layouts",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Ground rods cut to length with threaded ends (threads drawn at the major diameter): the displacer rods (Ø6, M6), the gamma's piston rod (Ø8, M8), the beta's hollow piston rod (Ø10 / Ø7, M10 × 1; the displacer rod runs inside it) and the Ø8 crank shafts the built-up cranks are pressed onto."
  ],
  "table": {
   "columns": [
    "part",
    "size"
   ],
   "rows": [
    [
     "rod-6x423.2-m6",
     "Ø6 × 423.20"
    ],
    [
     "rod-8x304.85-m8",
     "Ø8 × 304.85"
    ],
    [
     "rod-6x300.25-m6",
     "Ø6 × 300.25"
    ],
    [
     "tube-10x7x158.6-m10x1",
     "Ø10/7 × 158.60"
    ],
    [
     "shaft-8x56.5",
     "Ø8 × 56.50"
    ],
    [
     "shaft-8x88",
     "Ø8 × 88.00"
    ],
    [
     "shaft-8x46.3",
     "Ø8 × 46.30"
    ],
    [
     "shaft-8x103.95",
     "Ø8 × 103.95"
    ],
    [
     "shaft-8x138.3",
     "Ø8 × 138.30"
    ]
   ]
  }
 },
 "sheet_text": "Ground rods, hollow piston rod and crank shafts for the performance engines (Ø6, Ø8, Ø10 / 7) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/stirling-precision-rods/  (CC BY 4.0)\nBasis: Design values; lengths from the engines' layouts\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Ground rods cut to length with threaded ends (threads drawn at the major diameter): the displacer rods (Ø6, M6), the gamma's piston rod (Ø8, M8), the beta's hollow piston rod (Ø10 / Ø7, M10 × 1; the displacer rod runs inside it) and the Ø8 crank shafts the built-up cranks are pressed onto.\n\npart  size\nrod-6x423.2-m6  Ø6 × 423.20\nrod-8x304.85-m8  Ø8 × 304.85\nrod-6x300.25-m6  Ø6 × 300.25\ntube-10x7x158.6-m10x1  Ø10/7 × 158.60\nshaft-8x56.5  Ø8 × 56.50\nshaft-8x88  Ø8 × 88.00\nshaft-8x46.3  Ø8 × 46.30\nshaft-8x103.95  Ø8 × 103.95\nshaft-8x138.3  Ø8 × 138.30\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, 13 parts): https://xemstudio.com/files/hardware/stirling-precision-rods/index.json\nAPI: https://xemstudio.com/api/geometry?object=stirling-precision-rods\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": [
  "stirling-crosshead-yokes",
  "list-tri-clamp-horizontal-gamma",
  "list-tri-clamp-charged-beta"
 ],
 "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": "displacer rods",
   "exact": "Ø6, M6 × 12 ends",
   "mates": "gland bushings (run), cap and yoke M6 holes",
   "fit": "run",
   "files": "rod-6x"
  },
  {
   "feature": "piston rod",
   "exact": "Ø8, M8 × 12 ends",
   "mates": "gland bushings 8 × 12 × 20 (run)",
   "fit": "run",
   "files": "rod-8x"
  },
  {
   "feature": "hollow rod",
   "exact": "Ø10 / Ø7, M10 × 1 × 16 ends",
   "mates": "guide bushings 10 × 14 × 15 (run); Ø6 displacer rod inside (no contact)",
   "fit": "run",
   "files": "tube-10x7"
  },
  {
   "feature": "crank shafts",
   "exact": "Ø8",
   "mates": "crank webs (press), 608 bores, collars, flywheel, pulley",
   "fit": "press",
   "files": "shaft-8x"
  },
  {
   "feature": "transfer tube",
   "exact": "Ø12.7 × 0.89",
   "mates": "1/2 in tube compression fittings",
   "fit": "designed",
   "files": "transfer-tube"
  }
 ],
 "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 hollow piston rod?",
   "a": "In the beta the displacer rod runs inside it, coaxial."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "rod-6x423.2-m6",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/rod-6x423.2-m6.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/rod-6x423.2-m6.stl",
   "note": "Ø6 × 423.20 ground rod: horizontal gamma displacer rod, M6 × 12 both ends (drawn at Ø6)"
  },
  {
   "file": "rod-8x304.85-m8",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/rod-8x304.85-m8.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/rod-8x304.85-m8.stl",
   "note": "Ø8 × 304.85 ground rod: horizontal gamma piston rod, M8 × 12 both ends"
  },
  {
   "file": "rod-6x300.25-m6",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/rod-6x300.25-m6.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/rod-6x300.25-m6.stl",
   "note": "Ø6 × 300.25 ground rod: charged beta displacer rod, M6 × 12 both ends"
  },
  {
   "file": "rod-6x315.4-m6",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/rod-6x315.4-m6.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/rod-6x315.4-m6.stl",
   "note": "Ø6 × 315.40 ground rod: walking-beam gamma displacer rod, M6 × 12 both ends"
  },
  {
   "file": "transfer-tube-12.7x0.89x64",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/transfer-tube-12.7x0.89x64.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/transfer-tube-12.7x0.89x64.stl",
   "note": "transfer tube Ø12.7 × 0.89 wall × 64 (1/2 in tube) between the two 1/2 NPT fittings"
  },
  {
   "file": "tube-10x7x158.6-m10x1",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/tube-10x7x158.6-m10x1.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/tube-10x7x158.6-m10x1.stl",
   "note": "hollow piston rod Ø10 / Ø7 × 158.60, M10 × 1 × 16 both ends (drawn at Ø10)"
  },
  {
   "file": "shaft-8x56.5",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x56.5.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x56.5.stl",
   "note": "Ø8 × 56.50 crank shaft (pressed into the webs)"
  },
  {
   "file": "shaft-8x88",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x88.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x88.stl",
   "note": "Ø8 × 88.00 crank shaft (pressed into the webs)"
  },
  {
   "file": "shaft-8x46.3",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x46.3.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x46.3.stl",
   "note": "Ø8 × 46.30 crank shaft (pressed into the webs)"
  },
  {
   "file": "shaft-8x103.95",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x103.95.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x103.95.stl",
   "note": "Ø8 × 103.95 crank shaft (pressed into the webs)"
  },
  {
   "file": "shaft-8x138.3",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x138.3.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x138.3.stl",
   "note": "Ø8 × 138.30 crank shaft (pressed into the webs)"
  },
  {
   "file": "shaft-8x95.8",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x95.8.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x95.8.stl",
   "note": "Ø8 × 95.80 crank shaft (pressed into the webs)"
  },
  {
   "file": "shaft-8x91",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x91.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-precision-rods/shaft-8x91.stl",
   "note": "Ø8 × 91.00 crank shaft (twin: both webs pressed on it)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/stirling-precision-rods/index.md"
}