{
 "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-base",
 "name": "Test-tube marble engine base",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Stirling & thermoacoustic",
 "year": null,
 "question": "What base does a test-tube marble engine stand on?",
 "tags": [
  "marble engine",
  "base",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "marble stirling engine base"
 ],
 "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-base/",
 "sheet_txt": "https://xemstudio.com/objects/marble-engine-base/sheet.txt",
 "sheet": {
  "basis": "My geometry: holes on the pivot posts' and crank stands' foot patterns, M3 nut pockets at the nuts' exact 5.5 AF",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "438 × 100 × 8 (y −60..40). Two beam-pivot-post-60 at x 0, y ±10 (M3 × 12, nuts flush with the underside) and two crank-stand-80 at x 192.72, y −13.5 and −45.2 (M3 × 10, nuts 1 above the underside)."
  ],
  "table": {
   "columns": [
    "feature",
    "value"
   ],
   "rows": [
    [
     "base",
     "438 × 100 × 8"
    ],
    [
     "pivot posts",
     "x 0, y ±10"
    ],
    [
     "crank stands",
     "x 192.72"
    ]
   ]
  }
 },
 "sheet_text": "Test-tube marble engine base — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/marble-engine-base/  (CC BY 4.0)\nBasis: My geometry: holes on the pivot posts' and crank stands' foot patterns, M3 nut pockets at the nuts' exact 5.5 AF\nCatalog version: 2026-10-20\n\nSizes: see table below\n- 438 × 100 × 8 (y −60..40). Two beam-pivot-post-60 at x 0, y ±10 (M3 × 12, nuts flush with the underside) and two crank-stand-80 at x 192.72, y −13.5 and −45.2 (M3 × 10, nuts 1 above the underside).\n\nfeature  value\nbase  438 × 100 × 8\npivot posts  x 0, y ±10\ncrank stands  x 192.72\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, 1 parts): https://xemstudio.com/files/hardware/marble-engine-base/index.json\nAPI: https://xemstudio.com/api/geometry?object=marble-engine-base\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": [
  "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": "screw holes",
   "exact": "Ø3.4",
   "mates": "M3 clearance",
   "fit": "designed",
   "files": "all"
  },
  {
   "feature": "nut pockets",
   "exact": "5.5 AF hex",
   "mates": "ISO 4032 M3 nut",
   "fit": "press",
   "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 long is the marble engine?",
   "a": "The base is 438 mm: tube, stopper, transfer line, glass syringe and crank in one line."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "marble-engine-base",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/marble-engine-base/marble-engine-base.step",
   "stl": "https://xemstudio.com/files/hardware/marble-engine-base/marble-engine-base.stl",
   "note": "base 438 × 100 × 8 (y −60..40): 4 × Ø3.4 for the two pivot posts and 4 for the two crank stands, each with an M3 nut pocket (5.5 AF) from the underside"
  }
 ],
 "markdown": "https://xemstudio.com/objects/marble-engine-base/index.md"
}