{
 "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": "marble-engine-rocker",
 "name": "Test-tube marble engine rocker: tube and glass-syringe rings on a pivot",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "How do I hold the test tube of a marble Stirling engine so it rocks?",
 "tags": [
  "marble engine",
  "test tube",
  "rocker",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "test tube stirling engine holder",
  "marble stirling engine rocker",
  "test tube engine pivot"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/marble-engine-rocker/",
 "sheet_txt": "https://xemstudio.com/objects/marble-engine-rocker/sheet.txt",
 "sheet": {
  "basis": "My geometry: Ø25 ring at the 25 × 150 tube's OD (DURAN / KIMBLE 25 × 150), Ø15.40 ring at the 5 mL glass barrel's published OD (KD Scientific); tube and syringe on one axis so the transfer line never bends",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "The tube (hot end out, stopper toward the pivot) and the 5 mL glass syringe (tip toward the stopper) sit on one axis 18 above the pivot; the 4 mm tube through the stopper and a 50 mm silicone tube join them in a straight line, so nothing flexes as it rocks.",
   "Pivot: Ø3 bore for a dowel-3x30 through two beam-pivot-post-60 posts (hub 10 wide between them). Lever pin Ø3 at (35, −45) from the pivot for the 170 mm rocking link; with a 7.5 mm crank throw the rocker swings -7.9° to +7.9°.",
   "Rings: Ø25 × 12 for the tube, Ø15.40 × 12 for the syringe barrel, each with an M3 grub (set-m3x4, Ø2.5 tapped) that reaches the glass."
  ],
  "table": {
   "columns": [
    "feature",
    "value"
   ],
   "rows": [
    [
     "tube ring",
     "Ø25 × 12"
    ],
    [
     "syringe ring",
     "Ø15.40 × 12"
    ],
    [
     "axis above pivot",
     18
    ],
    [
     "lever pin",
     "(35, −45), Ø3"
    ],
    [
     "swing",
     "-7.9..7.9°"
    ]
   ]
  }
 },
 "sheet_text": "Test-tube marble engine rocker: tube and glass-syringe rings on a pivot — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/marble-engine-rocker/  (CC BY 4.0)\nBasis: My geometry: Ø25 ring at the 25 × 150 tube's OD (DURAN / KIMBLE 25 × 150), Ø15.40 ring at the 5 mL glass barrel's published OD (KD Scientific); tube and syringe on one axis so the transfer line never bends\nCatalog version: 2026-10-20\n\nSizes: see table below\n- The tube (hot end out, stopper toward the pivot) and the 5 mL glass syringe (tip toward the stopper) sit on one axis 18 above the pivot; the 4 mm tube through the stopper and a 50 mm silicone tube join them in a straight line, so nothing flexes as it rocks.\n- Pivot: Ø3 bore for a dowel-3x30 through two beam-pivot-post-60 posts (hub 10 wide between them). Lever pin Ø3 at (35, −45) from the pivot for the 170 mm rocking link; with a 7.5 mm crank throw the rocker swings -7.9° to +7.9°.\n- Rings: Ø25 × 12 for the tube, Ø15.40 × 12 for the syringe barrel, each with an M3 grub (set-m3x4, Ø2.5 tapped) that reaches the glass.\n\nfeature  value\ntube ring  Ø25 × 12\nsyringe ring  Ø15.40 × 12\naxis above pivot  18\nlever pin  (35, −45), Ø3\nswing  -7.9..7.9°\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- DWK / DURAN (via Parkes Scientific): DURAN test tubes 26 130: 25 × 150 mm, 55 mL, wall 1.0–1.2 mm (cat. 261303308) — web — listing [verify license at link] — https://parkesscientific.com/p/duran-26130-test-tubes-with-beaded-rim\n- DWK Life Sciences: KIMBLE reusable culture tube 25 × 150 mm, 55 mL (45048-25150) — web — manufacturer page [verify license at link] — https://www.dwk.com/na/kimble-reusable-culture-tube-25-x-150-mm-55-ml-45048-25150\n- KD Scientific: Full Line of Glass Syringes, rev. A (order codes 78-0871 to 78-0880): piston OD, barrel OD D1, barrel collar D2, piston collar D3, length L — PDF — manufacturer datasheet [verify license at link] — https://www.kdscientific.com/media/brochures/KDS%20Glass%20Syringe%20Datasheet.pdf\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, 1 parts): https://xemstudio.com/files/hardware/marble-engine-rocker/index.json\nAPI: https://xemstudio.com/api/geometry?object=marble-engine-rocker\n",
 "sources": [
  {
   "publisher": "DWK / DURAN (via Parkes Scientific)",
   "title": "DURAN test tubes 26 130: 25 × 150 mm, 55 mL, wall 1.0–1.2 mm (cat. 261303308)",
   "url": "https://parkesscientific.com/p/duran-26130-test-tubes-with-beaded-rim",
   "formats": [
    "web"
   ],
   "license": "listing",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "DWK Life Sciences",
   "title": "KIMBLE reusable culture tube 25 × 150 mm, 55 mL (45048-25150)",
   "url": "https://www.dwk.com/na/kimble-reusable-culture-tube-25-x-150-mm-55-ml-45048-25150",
   "formats": [
    "web"
   ],
   "license": "manufacturer page",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "KD Scientific",
   "title": "Full Line of Glass Syringes, rev. A (order codes 78-0871 to 78-0880): piston OD, barrel OD D1, barrel collar D2, piston collar D3, length L",
   "url": "https://www.kdscientific.com/media/brochures/KDS%20Glass%20Syringe%20Datasheet.pdf",
   "formats": [
    "PDF"
   ],
   "license": "manufacturer datasheet",
   "license_verified": false,
   "hosted": false
  },
  {
   "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": [
  "list-test-tube-marble-engine",
  "borosilicate-test-tubes",
  "glass-marbles",
  "glass-syringes",
  "rubber-stoppers",
  "beam-pivot-post"
 ],
 "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": "tube ring",
   "exact": "Ø25 × 12",
   "mates": "25 × 150 test tube OD",
   "fit": "socket",
   "files": "all"
  },
  {
   "feature": "syringe ring",
   "exact": "Ø15.40 × 12",
   "mates": "5 mL glass syringe barrel",
   "fit": "socket",
   "files": "all"
  },
  {
   "feature": "pivot bore",
   "exact": "Ø3",
   "mates": "dowel-3x30 pivot pin (turns in it)",
   "fit": "run",
   "files": "all"
  },
  {
   "feature": "lever pin bore",
   "exact": "Ø3",
   "mates": "dowel-3x12",
   "fit": "press",
   "files": "all"
  },
  {
   "feature": "grub holes",
   "exact": "Ø2.5 (M3 tapped)",
   "mates": "set-m3x4",
   "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": "How far does the tube of a marble engine rock?",
   "a": "About ±8° here: enough for the marbles to roll end to end each half turn."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "marble-engine-rocker-25x150-glass5",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/marble-engine-rocker/marble-engine-rocker-25x150-glass5.step",
   "stl": "https://xemstudio.com/files/hardware/marble-engine-rocker/marble-engine-rocker-25x150-glass5.stl",
   "note": "rocker: Ø25 ring for the 25 × 150 test tube and Ø15.40 ring for the 5 mL glass barrel on one axis 18 above the Ø3 pivot bore, beam 216 long, lever pin (Ø3) 45 below and 35 beside the pivot at the end of an arm reaching to y −72.5, 2 × M3 tapped (Ø2.5) grubs"
  }
 ],
 "markdown": "https://xemstudio.com/objects/marble-engine-rocker/index.md"
}