Kingston Dock Swing Bridge, Glasgow
This was a fascinating bridge, demolished in 1967. Fortunately its unusual engine is preserved, and is on display in the Scottish Maritime Museum, Irvine. See photos.
The bridge carried vehicular traffic over the entrance to the busy Kingston Dock. The dock was filled in and flats have been built on the site, which is immediately east of the M8 Kingston Bridge.
See Canmore entry, which includes excellent photographs.
The bridge was built in 1867 by John Yule and Co of Hutchesontown. It had three relatively shallow lattice girders, which were progressively strengthened over time to cope with heavier traffic. The bridge revolved on large iron wheels mounted in a cast iron frame attached to the underside of the bridge.
The most unusual aspect of the bridge was the mounting of the machinery. The engine was bolted to the underside of the bridge, and the boiler was suspended alongside the engine, and they rotated with it. The engine driver/fireman was also beneath the bridge, so he was presumably assisted by at least one banksman on top. The engine itself was unusual, following Yule's practice of having pairs of piston valves for each cylinder, one for steam admission, the other for exhaust, each valve requiring its own Stephenson's link motion.
George Watkins photographed the bridge in 1966, and recorded that opening took about 1 1/2 minutes from placing the barriers.[1]
An 1867 article[2] noted that the bridge was 39 ft wide, and the three 9 ft deep girders averaged 168 ft in length. The pivot was off-centre, so 100 tons of pig iron were provided for counter-balance. The design was credited to Mr Salmon, assistant to Mr Duncan, Engineer to the Clyde Trust. The article also stated that the bridge was hydraulically operated, the engine having two cylinders of 7 1/4" diameter and 18" stroke. This must be a mistake, and elsewhere the bridge was described as the Steam Swing Bridge[3]