I am hoping that someone on here could tell me a little about what powered swing bridges in the days before electricity. I imagine draft animals were used, but were there other options? Perhaps using the river current? Any examples would be greatly appreciated. Thanks!
They were operated by hand. Iron bars could be inserted into holes in an iron hub between the rails. With the leverage of the bars, a person could turn the hub, which was connected to a clockwork-like gear train at the center of the span where the slew bearing was mounted. The span pivoted on the bearing when one or more people pushed the bars that rotated the hub.
Some swing bridges were steam powered. IIRC the swing bridge at South Amboy NJ was steam powered into the 1960s or 1970s.