{
 "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": "list-tri-clamp-rd-ringbom",
 "name": "Build list: Tri-clamp rolling-diaphragm Ringbom, 2 in",
 "kind": "list",
 "category": "Stirling engines",
 "group": "Guide",
 "year": null,
 "question": "What parts do I need to build a Tri-clamp rolling-diaphragm Ringbom, 2 in?",
 "tags": [
  "list",
  "build",
  "stirling",
  "long earth society",
  "tri-clamp",
  "diaphragm",
  "ringbom",
  "rolling diaphragm",
  "torch"
 ],
 "aliases": [
  "ringbom stirling engine",
  "rolling diaphragm ringbom",
  "tri clamp ringbom",
  "free displacer stirling",
  "tri clamp stirling build list"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "not-scanned",
 "les": true,
 "free_files": 0,
 "url": "https://xemstudio.com/objects/list-tri-clamp-rd-ringbom/",
 "sheet_txt": "https://xemstudio.com/objects/list-tri-clamp-rd-ringbom/sheet.txt",
 "sheet": {
  "basis": "Every part is a free STEP/STL on this site or a standard part with its own page; quantities are the full count, every screw, nut, pin, gasket and clamp.",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "The simplest mechanism I could draw: one crank, one con-rod, and a free displacer that the gas pressure itself moves between two stops.",
   "Numbers: Numbers (Schmidt with the free displacer taken as a 90° sinusoid, the optional finned cooler on; a real Ringbom's timing depends on speed and load): power swept 20.0 mL, displacer swept 29.9 mL, dead volume 58 mL (swept/dead 0.34); Schmidt work at 650 / 320 K and 1 bar mean 0.33 J per turn (1.38 pressure ratio, ±16 kPa); shaft power about 0.3–1.1 W at 200–400 rpm (0.25–0.5 of Schmidt)."
  ],
  "table": {
   "columns": [
    "subsystem",
    "object",
    "parts",
    "qty",
    "note"
   ],
   "rows": [
    [
     null,
     "tri-clamp-rd-engine-frame",
     "rd-frame-2in",
     1,
     "base, wall, gussets"
    ],
    [
     null,
     "tri-clamp-torch-stand",
     "torch-stand-40",
     1,
     "on the base, post toward +Y; the heat source is a torch flame 40 mm under the cup"
    ],
    [
     null,
     "socket-head-cap-screws-metric",
     "shcs-m4x10",
     2,
     "torch stand to the base"
    ],
    [
     null,
     "set-screws-metric",
     "set-m4x10",
     3,
     "centre the torch head in the stand ring"
    ],
    [
     null,
     "tri-clamp-cups",
     "cup-2in-150",
     1,
     "the hot end and displacer cylinder in one piece: no joint near the flame"
    ],
    [
     null,
     "spool-hanger-collars",
     "hanger-2in-tab",
     1,
     "on the cup under the top clamp; bar to the wall"
    ],
    [
     null,
     "spool-hanger-collars",
     "hanger-2in-plain",
     1,
     "closes the hanger"
    ],
    [
     null,
     "socket-head-cap-screws-metric",
     "shcs-m5x25",
     2,
     "hanger bar through the wall"
    ],
    [
     null,
     "socket-head-cap-screws-metric",
     "shcs-m4x20",
     2,
     "hanger ears"
    ],
    [
     null,
     "hex-nuts-metric",
     "nut-m4",
     2,
     "hanger ears"
    ],
    [
     null,
     "tri-clamp-finned-cooler",
     "cooler-half-2in-56",
     2,
     "optional: clamp-on fin halves on the cup under the hanger (the cold end of the displacer cylinder); without them the engine runs with less power, or cool that part of the cup any way you like"
    ],
    [
     null,
     "socket-head-cap-screws-metric",
     "shcs-m4x30",
     4,
     "optional: cooler ears (only with the cooler)"
    ],
    [
     null,
     "hex-nuts-metric",
     "nut-m4",
     4,
     "optional: cooler ears (only with the cooler)"
    ],
    [
     null,
     "rolling-diaphragm-top-hat",
     "rd-diaphragm-1.50-h1.50",
     1,
     "1.50 in bore, 1.50 in high, flat flange: clamped in the joint in place of a gasket"
    ],
    [
     null,
     "tri-clamp-rd-power-head",
     "rd-power-head-2in",
     1,
     "standard 2 in clamp face, Ø38.10 cylinder, bushing seat, crank tower"
    ],
    [
     null,
     "tri-clamp-rd-power-head",
     "rd-seat-ring-2in",
     1,
     "in the head's face recess, behind the diaphragm flange"
    ],
    [
     null,
     "tri-clamp-clamps",
     "clamp-half-2in",
     6,
     "3 joints, two halves each"
    ],
    [
     null,
     "socket-head-cap-screws-metric",
     "shcs-m5x30",
     6,
     "clamp bolts"
    ],
    [
     null,
     "hex-nuts-metric",
     "nut-m5",
     8,
     "clamp nuts (6), hanger bar (2)"
    ],
    [
     null,
     "sleeve-bushings",
     "bushing-5x8x12",
     2,
     "back to back in the head's Ø8 seat: guide the tube rod"
    ],
    [
     null,
     "tri-clamp-rd-piston",
     "rd-piston-2in",
     1,
     "Ø33.27, never touches the bore"
    ],
    [
     null,
     "tri-clamp-rd-piston",
     "rd-retainer-26-blind",
     1,
     "clamps the diaphragm head on the crown"
    ],
    [
     null,
     "button-head-screws-metric",
     "button-m3x8",
     3,
     "retainer screws into the crown"
    ],
    [
     null,
     "tube-piston-rods-5mm",
     "tube-rod-5x3.4x80",
     1,
     "piston to yoke, through the bushings"
    ],
    [
     null,
     "tri-clamp-rd-yokes",
     "rd-yoke-tube5",
     1,
     "on the tube rod's end"
    ],
    [
     null,
     "set-screws-metric",
     "set-m3x3",
     1,
     "tube yoke grub"
    ],
    [
     null,
     "connecting-rods-623",
     "conrod-80",
     1,
     "power"
    ],
    [
     null,
     "counterweighted-crank-discs",
     "cw-crank-disc-stroke20",
     1,
     "20 mm stroke, overhung on the shaft end"
    ],
    [
     null,
     "stirling-crankshafts",
     "crankshaft-5x80-dflat",
     1,
     "disc face to flywheel hub"
    ],
    [
     null,
     "shaft-spacers",
     "spacer-5mm-t5",
     1,
     "disc hub to the front bearing"
    ],
    [
     null,
     "shaft-spacers",
     "spacer-5mm-t1",
     1,
     ""
    ],
    [
     null,
     "ball-bearings-metric",
     "bearing-625",
     2,
     "in the tower"
    ],
    [
     null,
     "shaft-collars",
     "collar-5mm",
     1,
     "behind the tower"
    ],
    [
     null,
     "nut-pocket-flywheels",
     "flywheel-150-m10-b5",
     1,
     "on the shaft's far end"
    ],
    [
     null,
     "hex-nut-weights",
     "nut-m10",
     18,
     "one in each rim pocket"
    ],
    [
     null,
     "sanitary-clamp-tees",
     "tee-2in",
     1,
     "standard 2 in equal tee: run upright on the cup, branch toward +X for the power head"
    ],
    [
     null,
     "tri-clamp-gasket",
     "tc-gasket-2in",
     2,
     "Type B: cup to tee, tee to gland cap"
    ],
    [
     null,
     "tri-clamp-rd-tee-inserts",
     "rd-tee-insert-2in-ringbom",
     1,
     "fills the tee's run between the two gasket lips"
    ],
    [
     null,
     "tri-clamp-rd-tee-inserts",
     "rd-branch-insert-2in",
     1,
     "fills the tee's branch; its spigot locates the run insert"
    ],
    [
     null,
     "tri-clamp-rd-gland-caps",
     "rd-gland-cap-2in-ringbom",
     1,
     "closes the top of the tee's run, carries the rod's gland"
    ],
    [
     null,
     "set-screws-metric",
     "set-m5x6",
     1,
     "plug in the gland cap's M5 port (or a gauge or one-way valve)"
    ],
    [
     null,
     "tri-clamp-displacer",
     "displacer-shell-2in-120",
     1,
     "Ø46 × 120, 0.75 radial gap, free: 18 mm between its stops"
    ],
    [
     null,
     "tri-clamp-ringbom-displacer-cap",
     "ringbom-cap-2in-r8",
     1,
     "closes the shell, holds the Ø8 rod"
    ],
    [
     null,
     "metric-shafts",
     "shaft-8x300",
     1,
     "the Ringbom rod: D-flat end in the cap, up through the tee insert and the gland"
    ],
    [
     null,
     "sleeve-bushings",
     "bushing-8x12x20",
     1,
     "in the gland cap's top: the rod's close-running gland"
    ],
    [
     null,
     "shaft-collars",
     "collar-8mm",
     1,
     "on the rod between the cap top and the bridge: the stops"
    ],
    [
     null,
     "set-screws-metric",
     "set-m4x4",
     2,
     "Ringbom cap and collar grubs"
    ],
    [
     null,
     "ball-bearings-metric",
     "bearing-623",
     2,
     "one in each con-rod eye"
    ],
    [
     null,
     "dowel-pins-metric",
     "dowel-3x12",
     2,
     "crank pin; tube-yoke stub pin"
    ],
    [
     null,
     "set-screws-metric",
     "set-m3x4",
     4,
     "grubs: piston, crank disc, collar, flywheel"
    ]
   ]
  }
 },
 "sheet_text": "Build list: Tri-clamp rolling-diaphragm Ringbom, 2 in — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/list-tri-clamp-rd-ringbom/  (CC BY 4.0)\nBasis: Every part is a free STEP/STL on this site or a standard part with its own page; quantities are the full count, every screw, nut, pin, gasket and clamp.\nCatalog version: 2026-10-20\n\nSizes: see table below\n- The simplest mechanism I could draw: one crank, one con-rod, and a free displacer that the gas pressure itself moves between two stops.\n- Numbers: Numbers (Schmidt with the free displacer taken as a 90° sinusoid, the optional finned cooler on; a real Ringbom's timing depends on speed and load): power swept 20.0 mL, displacer swept 29.9 mL, dead volume 58 mL (swept/dead 0.34); Schmidt work at 650 / 320 K and 1 bar mean 0.33 J per turn (1.38 pressure ratio, ±16 kPa); shaft power about 0.3–1.1 W at 200–400 rpm (0.25–0.5 of Schmidt).\n\nsubsystem  object  parts  qty  note\nNone  tri-clamp-rd-engine-frame  rd-frame-2in  1  base, wall, gussets\nNone  tri-clamp-torch-stand  torch-stand-40  1  on the base, post toward +Y; the heat source is a torch flame 40 mm under the cup\nNone  socket-head-cap-screws-metric  shcs-m4x10  2  torch stand to the base\nNone  set-screws-metric  set-m4x10  3  centre the torch head in the stand ring\nNone  tri-clamp-cups  cup-2in-150  1  the hot end and displacer cylinder in one piece: no joint near the flame\nNone  spool-hanger-collars  hanger-2in-tab  1  on the cup under the top clamp; bar to the wall\nNone  spool-hanger-collars  hanger-2in-plain  1  closes the hanger\nNone  socket-head-cap-screws-metric  shcs-m5x25  2  hanger bar through the wall\nNone  socket-head-cap-screws-metric  shcs-m4x20  2  hanger ears\nNone  hex-nuts-metric  nut-m4  2  hanger ears\nNone  tri-clamp-finned-cooler  cooler-half-2in-56  2  optional: clamp-on fin halves on the cup under the hanger (the cold end of the displacer cylinder); without them the engine runs with less power, or cool that part of the cup any way you like\nNone  socket-head-cap-screws-metric  shcs-m4x30  4  optional: cooler ears (only with the cooler)\nNone  hex-nuts-metric  nut-m4  4  optional: cooler ears (only with the cooler)\nNone  rolling-diaphragm-top-hat  rd-diaphragm-1.50-h1.50  1  1.50 in bore, 1.50 in high, flat flange: clamped in the joint in place of a gasket\nNone  tri-clamp-rd-power-head  rd-power-head-2in  1  standard 2 in clamp face, Ø38.10 cylinder, bushing seat, crank tower\nNone  tri-clamp-rd-power-head  rd-seat-ring-2in  1  in the head's face recess, behind the diaphragm flange\nNone  tri-clamp-clamps  clamp-half-2in  6  3 joints, two halves each\nNone  socket-head-cap-screws-metric  shcs-m5x30  6  clamp bolts\nNone  hex-nuts-metric  nut-m5  8  clamp nuts (6), hanger bar (2)\nNone  sleeve-bushings  bushing-5x8x12  2  back to back in the head's Ø8 seat: guide the tube rod\nNone  tri-clamp-rd-piston  rd-piston-2in  1  Ø33.27, never touches the bore\nNone  tri-clamp-rd-piston  rd-retainer-26-blind  1  clamps the diaphragm head on the crown\nNone  button-head-screws-metric  button-m3x8  3  retainer screws into the crown\nNone  tube-piston-rods-5mm  tube-rod-5x3.4x80  1  piston to yoke, through the bushings\nNone  tri-clamp-rd-yokes  rd-yoke-tube5  1  on the tube rod's end\nNone  set-screws-metric  set-m3x3  1  tube yoke grub\nNone  connecting-rods-623  conrod-80  1  power\nNone  counterweighted-crank-discs  cw-crank-disc-stroke20  1  20 mm stroke, overhung on the shaft end\nNone  stirling-crankshafts  crankshaft-5x80-dflat  1  disc face to flywheel hub\nNone  shaft-spacers  spacer-5mm-t5  1  disc hub to the front bearing\nNone  shaft-spacers  spacer-5mm-t1  1  \nNone  ball-bearings-metric  bearing-625  2  in the tower\nNone  shaft-collars  collar-5mm  1  behind the tower\nNone  nut-pocket-flywheels  flywheel-150-m10-b5  1  on the shaft's far end\nNone  hex-nut-weights  nut-m10  18  one in each rim pocket\nNone  sanitary-clamp-tees  tee-2in  1  standard 2 in equal tee: run upright on the cup, branch toward +X for the power head\nNone  tri-clamp-gasket  tc-gasket-2in  2  Type B: cup to tee, tee to gland cap\nNone  tri-clamp-rd-tee-inserts  rd-tee-insert-2in-ringbom  1  fills the tee's run between the two gasket lips\nNone  tri-clamp-rd-tee-inserts  rd-branch-insert-2in  1  fills the tee's branch; its spigot locates the run insert\nNone  tri-clamp-rd-gland-caps  rd-gland-cap-2in-ringbom  1  closes the top of the tee's run, carries the rod's gland\nNone  set-screws-metric  set-m5x6  1  plug in the gland cap's M5 port (or a gauge or one-way valve)\nNone  tri-clamp-displacer  displacer-shell-2in-120  1  Ø46 × 120, 0.75 radial gap, free: 18 mm between its stops\nNone  tri-clamp-ringbom-displacer-cap  ringbom-cap-2in-r8  1  closes the shell, holds the Ø8 rod\nNone  metric-shafts  shaft-8x300  1  the Ringbom rod: D-flat end in the cap, up through the tee insert and the gland\nNone  sleeve-bushings  bushing-8x12x20  1  in the gland cap's top: the rod's close-running gland\nNone  shaft-collars  collar-8mm  1  on the rod between the cap top and the bridge: the stops\nNone  set-screws-metric  set-m4x4  2  Ringbom cap and collar grubs\nNone  ball-bearings-metric  bearing-623  2  one in each con-rod eye\nNone  dowel-pins-metric  dowel-3x12  2  crank pin; tube-yoke stub pin\nNone  set-screws-metric  set-m3x4  4  grubs: piston, crank disc, collar, flywheel\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\nXem Studio scan: not planned; the official CAD above covers it.\nAPI: https://xemstudio.com/api/geometry?object=list-tri-clamp-rd-ringbom\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": "not-scanned",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "tri-clamp-rd-gland-caps",
  "tri-clamp-rd-tee-inserts",
  "sanitary-clamp-tees",
  "tri-clamp-ringbom-displacer-cap",
  "rolling-diaphragm-top-hat",
  "tri-clamp-rd-power-head",
  "tri-clamp-rd-engine-frame",
  "tri-clamp-finned-cooler",
  "list-tri-clamp-rd-gamma"
 ],
 "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": [],
 "faq": [
  {
   "q": "What is a Ringbom engine?",
   "a": "50 parts, every one a free STEP/STL on this site; see the table and the build order on this page."
  },
  {
   "q": "Will it start by itself?",
   "a": "No more than any Stirling engine: give the flywheel a spin once the cup is hot. If the displacer does not move, it is too heavy for the pressure swing."
  },
  {
   "q": "Can I make it crank-driven later?",
   "a": "Yes: the gamma uses the same cup, tee, frame and power head."
  },
  {
   "q": "Do I need the finned cooler?",
   "a": "No. It is an optional heat exchanger that clamps on the plain cup; without it the engine runs with less power. Any cooling of the top of the cup works, even a wet rag. The numbers above assume the cold end held near 320 K."
  }
 ],
 "files_license": null,
 "offers": [],
 "markdown": "https://xemstudio.com/objects/list-tri-clamp-rd-ringbom/index.md"
}