{
  "schema_version": "1.0",
  "rubrics": [
    {
      "id": "R1",
      "requirement": "The model shall be a single part whose overall length along the shaft axis is 253 mm."
    },
    {
      "id": "R2",
      "requirement": "The model shall have a blade envelope measuring 170 mm by 154.72 mm in the view along the shaft axis."
    },
    {
      "id": "R3",
      "requirement": "The model shall have exactly six blades on the head, equally spaced at 60° about the shaft axis."
    },
    {
      "id": "R4",
      "requirement": "The model shall have blades that are twisted (helically swept) along the curved conical head profile rather than straight radial fins."
    },
    {
      "id": "R5",
      "requirement": "The model shall have a head that tapers along the axis toward its end face, with a domed/bell-shaped outer blade profile."
    },
    {
      "id": "R6",
      "requirement": "The model shall include a thin collar flange between the blade root and the journal, sized to an R45 circle."
    },
    {
      "id": "R7",
      "requirement": "The model shall include a cylindrical bearing journal of radius 39 mm coaxial with the head."
    },
    {
      "id": "R8",
      "requirement": "The model shall include a necked section with a concave rounded circumferential groove between the journal and the spline."
    },
    {
      "id": "R9",
      "requirement": "The model shall include a splined section with rectangular axial teeth evenly spaced around the axis."
    },
    {
      "id": "R10",
      "requirement": "The model shall end in a plain cylindrical spigot with a flat end face beyond the spline."
    },
    {
      "id": "R11",
      "requirement": "The model shall have all revolved features (head, collar, journal, neck, spline core, spigot) coaxial on one axis."
    },
    {
      "id": "R12",
      "requirement": "The model shall be dimensioned in millimetres."
    }
  ]
}