{
 "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-rd-power-head",
 "name": "Tri-clamp rolling-diaphragm power head, 2 in: standard clamp face, cylinder, rod guide and crank tower, with its diaphragm seat ring",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "How do I mount a rolling diaphragm power piston on a tri-clamp fitting?",
 "tags": [
  "power head",
  "rolling diaphragm",
  "crank",
  "cylinder",
  "tri-clamp",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "rolling diaphragm power cylinder",
  "tri clamp power piston head",
  "stirling power head tri clamp",
  "rolling diaphragm cylinder",
  "rolling diaphragm seat ring"
 ],
 "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-rd-power-head/",
 "sheet_txt": "https://xemstudio.com/objects/tri-clamp-rd-power-head/sheet.txt",
 "sheet": {
  "basis": "ISO 2852 face, rim, recess and 20° back cone as the flat end cap on this site; rolling-diaphragm bore, radii and stroke from the published 1.50 in size; 625 and 5 × 8 × 12 bushing sizes from their standards; crank geometry is a design value",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "One part behind a standard 2 in clamp joint. Its clamped end is a standard ISO 2852 2 in face: the land, the 2.85 mm rim, the 1.6 mm recess inside Ø56.5 and the 20° back cone, exactly as an end cap's, so the standard clamp closes on it and it goes on any 2 in ferrule.",
   "The diaphragm's flange (0.51) takes the place of the gasket. Between the flange and the head sits the seat ring: 1.19 mm on the land and down into the head's recess inside Ø56.5, so flange plus ring are the 1.7 mm of a Type B gasket's web and the clamp closes exactly as it does on a gasket. The ring carries the 1/16 in mouth radius the diaphragm wall rolls off, and its Ø38.10 bore runs on into the head's.",
   "Behind the ring: the Ø38.10 bore the diaphragm rolls in, down to a floor 49 mm from the clamp plane with four Ø6 vents so the back of the diaphragm is at air pressure; a Ø16 boss with an Ø8 seat for two 5 × 8 × 12 sleeve bushings that guide the Ø5 tube piston rod.",
   "A tower on −Y carries two 625 bearings (Ø16 × 5 pockets, 24 apart) on a Ø5 crankshaft 188 mm from the clamp plane: a 20 mm stroke crank disc on the shaft end, a conrod-80 down to the rod yoke. The flywheel goes on the far end.",
   "The same head goes on the 2 in cup of the beta (straight up) and on the branch of a standard 2 in tee in the Ringbom and gamma (sideways)."
  ],
  "table": {
   "columns": [
    "feature",
    "value_mm"
   ],
   "rows": [
    [
     "clamp face",
     "ISO 2852 2 in, face plane 0.85 from the clamp plane"
    ],
    [
     "seat ring on the land",
     1.19
    ],
    [
     "seat ring in the recess",
     2.79
    ],
    [
     "bore Ø",
     38.1
    ],
    [
     "bore depth",
     49
    ],
    [
     "bushing seat",
     "Ø8 × 24"
    ],
    [
     "bearing pockets",
     "Ø16 × 5, y −26 and −50"
    ],
    [
     "shaft axis",
     188
    ],
    [
     "stroke",
     20
    ]
   ]
  }
 },
 "sheet_text": "Tri-clamp rolling-diaphragm power head, 2 in: standard clamp face, cylinder, rod guide and crank tower, with its diaphragm seat ring — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/tri-clamp-rd-power-head/  (CC BY 4.0)\nBasis: ISO 2852 face, rim, recess and 20° back cone as the flat end cap on this site; rolling-diaphragm bore, radii and stroke from the published 1.50 in size; 625 and 5 × 8 × 12 bushing sizes from their standards; crank geometry is a design value\nCatalog version: 2026-10-20\n\nSizes: see table below\n- One part behind a standard 2 in clamp joint. Its clamped end is a standard ISO 2852 2 in face: the land, the 2.85 mm rim, the 1.6 mm recess inside Ø56.5 and the 20° back cone, exactly as an end cap's, so the standard clamp closes on it and it goes on any 2 in ferrule.\n- The diaphragm's flange (0.51) takes the place of the gasket. Between the flange and the head sits the seat ring: 1.19 mm on the land and down into the head's recess inside Ø56.5, so flange plus ring are the 1.7 mm of a Type B gasket's web and the clamp closes exactly as it does on a gasket. The ring carries the 1/16 in mouth radius the diaphragm wall rolls off, and its Ø38.10 bore runs on into the head's.\n- Behind the ring: the Ø38.10 bore the diaphragm rolls in, down to a floor 49 mm from the clamp plane with four Ø6 vents so the back of the diaphragm is at air pressure; a Ø16 boss with an Ø8 seat for two 5 × 8 × 12 sleeve bushings that guide the Ø5 tube piston rod.\n- A tower on −Y carries two 625 bearings (Ø16 × 5 pockets, 24 apart) on a Ø5 crankshaft 188 mm from the clamp plane: a 20 mm stroke crank disc on the shaft end, a conrod-80 down to the rod yoke. The flywheel goes on the far end.\n- The same head goes on the 2 in cup of the beta (straight up) and on the branch of a standard 2 in tee in the Ringbom and gamma (sideways).\n\nfeature  value_mm\nclamp face  ISO 2852 2 in, face plane 0.85 from the clamp plane\nseat ring on the land  1.19\nseat ring in the recess  2.79\nbore Ø  38.1\nbore depth  49.0\nbushing seat  Ø8 × 24\nbearing pockets  Ø16 × 5, y −26 and −50\nshaft axis  188.0\nstroke  20.0\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- ISO (via iTeh sample): ISO 2852 clamp liners: face profile and flange / groove diameters — PDF — standard excerpt; dimensions are facts — https://cdn.standards.iteh.ai/samples/7850/eb49c396488d408c8ced3e2961d76cf3/ISO-2852-1974.pdf\n- ASME: BPE Bioprocessing Equipment (clamp fitting dimensions, tube OD and wall) — standard — ASME; dimensions are facts [verify license at link] — https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment\n- Marsh Bellofram: Rolling diaphragm design manual (2022): nomenclature, height formula, standard-size tables, hardware radii — PDF — publisher's manual; dimensions cited, nothing copied — https://damapi.marshbellofram.com/uploads/Bellofram_Diaphragm_Design_Manual_2022_7a922642c3.pdf\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-rd-power-head/index.json\nAPI: https://xemstudio.com/api/geometry?object=tri-clamp-rd-power-head\n",
 "sources": [
  {
   "publisher": "ISO (via iTeh sample)",
   "title": "ISO 2852 clamp liners: face profile and flange / groove diameters",
   "url": "https://cdn.standards.iteh.ai/samples/7850/eb49c396488d408c8ced3e2961d76cf3/ISO-2852-1974.pdf",
   "formats": [
    "PDF"
   ],
   "license": "standard excerpt; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "ASME",
   "title": "BPE Bioprocessing Equipment (clamp fitting dimensions, tube OD and wall)",
   "url": "https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment",
   "formats": [
    "standard"
   ],
   "license": "ASME; dimensions are facts",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Marsh Bellofram",
   "title": "Rolling diaphragm design manual (2022): nomenclature, height formula, standard-size tables, hardware radii",
   "url": "https://damapi.marshbellofram.com/uploads/Bellofram_Diaphragm_Design_Manual_2022_7a922642c3.pdf",
   "formats": [
    "PDF"
   ],
   "license": "publisher's manual; dimensions cited, nothing copied",
   "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": [
  "rolling-diaphragm-top-hat",
  "tri-clamp-rd-piston",
  "tri-clamp-rd-yokes",
  "tri-clamp-rd-link-webs",
  "sleeve-bushings",
  "list-tri-clamp-rd-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": "clamp face",
   "exact": "ISO 2852 2 in (land Ø56.5–Ø64.0, rim 2.85, 1.6 recess, 20° back), face plane 0.85 from the clamp plane",
   "mates": "2 in clamp; seat ring and diaphragm flange in place of a gasket",
   "fit": "clamp",
   "files": "rd-power-head"
  },
  {
   "feature": "face recess",
   "exact": "Ø56.5 × 1.6",
   "mates": "seat ring (fills it)",
   "fit": "slide",
   "files": "rd-power-head"
  },
  {
   "feature": "cylinder bore",
   "exact": "Ø38.10 from the recess floor to 49",
   "mates": "rolling diaphragm outer wall (piston 2.41 clear)",
   "fit": "designed",
   "files": "rd-power-head"
  },
  {
   "feature": "seat ring OD in the recess",
   "exact": "Ø56.5 × 1.6",
   "mates": "power head face recess",
   "fit": "slide",
   "files": "rd-seat-ring"
  },
  {
   "feature": "seat ring on the land",
   "exact": "Ø56.5–Ø63.5 × 1.19",
   "mates": "power head land and the diaphragm flange (flange + ring = 1.7, a Type B web)",
   "fit": "clamp",
   "files": "rd-seat-ring"
  },
  {
   "feature": "seat ring bore",
   "exact": "Ø38.10, 1/16 in mouth radius",
   "mates": "rolling diaphragm wall (rolls off the radius)",
   "fit": "designed",
   "files": "rd-seat-ring"
  },
  {
   "feature": "bushing seat",
   "exact": "Ø8 × 24",
   "mates": "two 5 × 8 × 12 sleeve bushings",
   "fit": "press",
   "files": "all"
  },
  {
   "feature": "bearing pockets",
   "exact": "Ø16 × 5 (two)",
   "mates": "625 bearing",
   "fit": "press",
   "files": "all"
  },
  {
   "feature": "shaft passage",
   "exact": "Ø8",
   "mates": "Ø5 crankshaft (no contact)",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "floor vents",
   "exact": "4 × Ø6",
   "mates": "air (back of the diaphragm)",
   "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": "Does it fit a standard clamp?",
   "a": "Yes: its clamped end is a standard 2 in face, and flange plus seat ring are as thick as a gasket's web."
  },
  {
   "q": "Where does the gasket go?",
   "a": "There is none at this joint: the diaphragm's flange is the seal, with the seat ring behind it."
  },
  {
   "q": "Why the vents?",
   "a": "So the back of the diaphragm and the piston's skirt stay at air pressure; otherwise the space would act as a spring and pump through the bushings."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "rd-power-head-2in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-rd-power-head/rd-power-head-2in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-rd-power-head/rd-power-head-2in.stl",
   "note": "2 in rolling-diaphragm power head: standard ISO 2852 2 in clamp face (land Ø56.5–Ø64, rim 2.85, recess 1.6 inside Ø56.5, 20° back cone; face plane 0.85 from the clamp plane), Ø38.10 bore from the recess floor to 49, floor 6 with 4 × Ø6 vents, Ø16 boss with an Ø8 × 24 seat for two 5 × 8 × 12 bushings, crank tower with two Ø16 × 5 bearing pockets on the shaft axis 188 above the clamp plane"
  },
  {
   "file": "rd-seat-ring-2in",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/tri-clamp-rd-power-head/rd-seat-ring-2in.step",
   "stl": "https://xemstudio.com/files/hardware/tri-clamp-rd-power-head/rd-seat-ring-2in.stl",
   "note": "diaphragm seat ring: Ø63.5 × 1.19 on the land (Ø56.5–Ø63.5), 2.79 thick inside Ø56.5 (fills the head's 1.6 recess), bore Ø38.10 with the 1/16 in mouth radius"
  }
 ],
 "markdown": "https://xemstudio.com/objects/tri-clamp-rd-power-head/index.md"
}