{
  "revision": "lightweight-brief-2",
  "date": "2026-10-19",
  "status": "Requirements fixed for concept comparison; neither concept is selected, load-rated or approved for fabrication",
  "objective": "Reduce the installed weight of the dance-floor and sheep-support systems while preserving the shared functional requirements",
  "requirements": {
    "people": 20,
    "person_allowance_lb": 225,
    "total_people_allowance_lb": 4500,
    "use": "Dancing while the bus moves at up to 5 mph",
    "maximum_event_speed_mph": 5,
    "deck_footprint_m": [
      11.396,
      2.6984
    ],
    "deck_surface_height_m": 3.4004,
    "deck_geometry_basis": "Preserve current modeled footprint and height for both concepts; donor geometry remains unmeasured",
    "exterior_panel_count": 206,
    "road_width_maximum_in": 102,
    "road_requirement_source": "project-constraints.json",
    "road_retained": "Donor bus, all permanent supports and every retained fitting",
    "road_removed": "Roof deck/removable frame, sheep panels, projecting support assemblies, speakers and event equipment",
    "removable_connections": true
  },
  "variables": [
    "Station count and positions, subject to actual attachment access",
    "Member geometry, material specification and wall thickness",
    "Floor joist arrangement and deck construction",
    "Truss layout and available depth without changing the deck height",
    "Transverse bracing, removable connections and module sizes",
    "Panel subframes and dedicated equipment supports"
  ],
  "concepts": [
    {
      "id": "six",
      "name": "Optimized six-station frame",
      "station_ids": [
        "A",
        "B",
        "C",
        "D",
        "E",
        "F"
      ],
      "status": "Concept; existing v5 is a mass and geometry reference only"
    },
    {
      "id": "four",
      "name": "Four-station frame with longitudinal trusses",
      "station_ids": [
        "A",
        "C",
        "D",
        "F"
      ],
      "status": "Concept; retained positions are a first comparison, not optimized or field-verified"
    }
  ],
  "deferred_measurements": [
    "Actual exterior and rub-rail width and clearances along uprights",
    "Chassis rail dimensions, spacing, condition and accessible attachments",
    "Scale weights, axle loads, GVWR and axle/tire ratings",
    "Equipment weights and locations, including speakers and head"
  ],
  "unresolved_engineering": [
    "Acceleration, braking, cornering, bumps, synchronized dancing, wind and fatigue loads",
    "Floor vibration, crowd distribution and frame reactions",
    "Transverse stability and removable joint stiffness/strength",
    "Chassis attachment uplift, bearing, torsion and body/chassis movement",
    "Whole-vehicle stability and complete road configuration"
  ],
  "not_adopted": [
    "Rub-rail cutting or welding uprights to the bus body",
    "Using the existing body as an assumed dance-floor support",
    "Treating a 2x live-load sensitivity as a validated dancing factor",
    "Any final member sizes, connection details or fabrication drawings"
  ],
  "interior_investigation": {
    "page": "interior-supports.html",
    "data": "interior-support-study.json",
    "basis": "User confirms BAAAHS has individual cabin posts, not paired wall portals. Exact structure unknown.",
    "trials": "Three and four individual posts; centerline, over one rail, or near one wall. Illustrative positions only.",
    "status": "Supplementary concept investigation; no final sections, mass, capacity or road-envelope acceptance."
  }
}