Structures: Steam dynamo

{
  "cost": {
    "steel": 12,
    "gear": 4,
    "shaft": 2,
    "bearing": 4,
    "standard-parts": 4,
    "insulated-winding": 4,
    "field-magnet": 2,
    "glass": 4
  },
  "seconds": 180,
  "description": "A fixed line-shaft dynamo for a staffed local carbon-arc lighthouse beacon; it stores no electricity."
}