{
 "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-clearance-seal-pistons",
 "name": "Clearance-seal pistons Ø48.00 × 34 for a bored 2 in spool: rod (gamma) and gland (beta)",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "What piston goes in a bored and honed 2 in tri-clamp spool?",
 "tags": [
  "piston",
  "clearance seal",
  "power piston",
  "tri-clamp",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "clearance seal piston",
  "tri clamp piston",
  "stirling power piston 48 mm"
 ],
 "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/stirling-clearance-seal-pistons/",
 "sheet_txt": "https://xemstudio.com/objects/stirling-clearance-seal-pistons/sheet.txt",
 "sheet": {
  "basis": "Design values; leakage from plane Poiseuille flow in the clearance (Hagen–Poiseuille)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Ø48.00 × 34, no rings: the ground OD in the honed Ø48.00 bore is the seal. It is driven through a rod and a crosshead guided outside the cylinder, so it carries no side load and keeps its clearance.",
   "Gamma piston: the Ø8 rod screws into the boss and is locked with an M8 nut on the boss end.",
   "Beta piston: the displacer rod passes through a 6 × 10 × 10 sleeve bushing at the crown (its gland), and the hollow Ø10 piston rod screws into the boss until it bottoms.",
   "Leakage loss in the cycle model (charged air, 600 rpm): 0.44 / 1.50 / 3.54 W at 10 / 15 / 20 µm radial clearance on the gamma."
  ],
  "table": {
   "columns": [
    "part",
    "od_mm",
    "length_mm",
    "rod"
   ],
   "rows": [
    [
     "piston-48-gamma-m8",
     48,
     34,
     "M8 socket"
    ],
    [
     "piston-48-beta-gland",
     48,
     34,
     "gland + M10 × 1 socket"
    ]
   ]
  }
 },
 "sheet_text": "Clearance-seal pistons Ø48.00 × 34 for a bored 2 in spool: rod (gamma) and gland (beta) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/stirling-clearance-seal-pistons/  (CC BY 4.0)\nBasis: Design values; leakage from plane Poiseuille flow in the clearance (Hagen–Poiseuille)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Ø48.00 × 34, no rings: the ground OD in the honed Ø48.00 bore is the seal. It is driven through a rod and a crosshead guided outside the cylinder, so it carries no side load and keeps its clearance.\n- Gamma piston: the Ø8 rod screws into the boss and is locked with an M8 nut on the boss end.\n- Beta piston: the displacer rod passes through a 6 × 10 × 10 sleeve bushing at the crown (its gland), and the hollow Ø10 piston rod screws into the boss until it bottoms.\n- Leakage loss in the cycle model (charged air, 600 rpm): 0.44 / 1.50 / 3.54 W at 10 / 15 / 20 µm radial clearance on the gamma.\n\npart  od_mm  length_mm  rod\npiston-48-gamma-m8  48.0  34.0  M8 socket\npiston-48-beta-gland  48.0  34.0  gland + M10 × 1 socket\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Hagen–Poiseuille equation: annular clearance leakage Q = π D δ³ Δp / 12 μ L — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Hagen%E2%80%93Poiseuille_equation\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/stirling-clearance-seal-pistons/index.json\nAPI: https://xemstudio.com/api/geometry?object=stirling-clearance-seal-pistons\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Hagen–Poiseuille equation: annular clearance leakage Q = π D δ³ Δp / 12 μ L",
   "url": "https://en.wikipedia.org/wiki/Hagen%E2%80%93Poiseuille_equation",
   "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": [
  "tri-clamp-spool-bored-honed",
  "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": "OD",
   "exact": "Ø48.00 × 34",
   "mates": "honed bore Ø48.00 (clearance seal)",
   "fit": "run",
   "files": "all"
  },
  {
   "feature": "rod socket",
   "exact": "M8 tapped (Ø6.8) z 8–20",
   "mates": "Ø8 rod, M8 end",
   "fit": "designed",
   "files": "piston-48-gamma"
  },
  {
   "feature": "gland seat",
   "exact": "Ø10 × 10 at the crown",
   "mates": "6 × 10 × 10 sleeve bushing",
   "fit": "press",
   "files": "piston-48-beta"
  },
  {
   "feature": "tube socket",
   "exact": "M10 × 1 tapped (Ø9.0) z 14–30",
   "mates": "hollow rod, M10 × 1 end",
   "fit": "designed",
   "files": "piston-48-beta"
  }
 ],
 "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 clearance?",
   "a": "The fit class is a running fit to the honed bore; the leakage table shows what 10, 15 and 20 µm radial cost."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "piston-48-gamma-m8",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-clearance-seal-pistons/piston-48-gamma-m8.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-clearance-seal-pistons/piston-48-gamma-m8.stl",
   "note": "clearance-seal piston Ø48.00 × 34: crown 6, skirt 3, boss Ø18 with an M8 tapped (Ø6.8) socket z 8–20 for the rod"
  },
  {
   "file": "piston-48-beta-gland",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/stirling-clearance-seal-pistons/piston-48-beta-gland.step",
   "stl": "https://xemstudio.com/files/hardware/stirling-clearance-seal-pistons/piston-48-beta-gland.stl",
   "note": "clearance-seal piston Ø48.00 × 34 for a beta: Ø10 × 10 gland seat at the crown (6 × 10 × 10 bushing, the displacer rod's gland), Ø7 on, M10 × 1 tapped (Ø9.0) socket z 14–30 for the hollow rod"
  }
 ],
 "markdown": "https://xemstudio.com/objects/stirling-clearance-seal-pistons/index.md"
}