Clarence Swing Bridge, Cardiff
NO LONGER EXTANT. Demolished in 1975 and replaced by a box girder bridge.
Built c.1890 to replace an earlier swing bridge carrying Ferry Road over the River Taff.
Coflein entry here.
Decribed in detail in Engineering in 1891 [1] [2] [3] [4]
Designed by William Harpur.
Swinging span: length 190 ft 8". Two approach spans, each 132 ft.
The bridge had some features which were followed American practice but were unusual in Britain. In particular, pin-jointed Pratt trusses were adopted, as widely used at the time in the USA. In fact, although the eye bars for the trusses were rolled by the Steel Company of Scotland, they were sent to the USA to have the heads die forged (apparently by the Union Bridge Co, New York). This suggests that the specialised machinery for forging the eyes was not available in Britain due to the lack of demand for that type of eye bar. However, Braithwaite and Kirk wrote to Engineering stating that they had long been producing such bars, while shortly afterwards a letter from Charles Wawn of the Patent Shaft and Axletree Co to Engineering 1891/02/27 stated that 'The manufacture of such links is almost a speciality with us. Amongst many others we have within the last few years made about forty link spans of 200ft. for the Imperial Railways of Japan, and we have now in our yard a bridge of 60 metres, with links 29 ft. long, and up to 1 1/2 in. thick, for a company for whom we have made several other large bridges of this description.'
William Harpur used similar eye bars in his Cardiff Central Market. See photo.
Note: Wrought iron eye bars had been widely used as chain links on British-built suspension bridges, and occasionally for the bottom chords of girder bridges (including the High Level Bridge, Newcastle and Joiner Street Bridge in London, and for diagonal ties on the bowstring girders of Windsor Railway Bridge. They were also used for the bottom cords of arched Warren truss roof supports at Liverpool Lime Street Railway Station. Initially the eyes had been fire-welded onto the link, but in 1845 Howard, Ravenhill and Co developed a method of rolling the bars with swelled ends. The firm produced many of these links until it closed down in the early 1870s.
It appears that the Steel Co of Scotland used the process patented in the USA by Andrew Kloman to roll the steel bars with enlarged ends ready for die forging into eye bars. The process was simple in principle, but it reqiured a special type of rolling mill. This worked on the principle of a universal rolling mill, having a pair of vertical rolls in series with a pair of horizontal rolls. The product was a rectangular bar, most of whose length was progressivly reduced in thickness by passing it back and forth through the horizontal rolls, which were incrementally brought together. It was realised (by whom?) that the bars could be used for the chords of the Clarence Bridge without forming the rounded eye ends, and just leaving the ends of bars with rectangular bosses, thicker than the shank of the bar.
The whole of the c.500 ton weight of the swinging span rested entirely on the central pier, not only when the bridge was swinging, but also when closed and ready to receive the road traffic. It was believed that this was the first swing bridge constructed on this principle in the UK, the usual method being to raise the ends of the span by cams, wedges, or other means, so as to bring the main girders into the condition of stress obtained in a continuous girder resting on three supports.
The masonry piers and abutments and the timber dolphins were executed by Logan and Hemingway. Andrew Handyside and Co of Derby manufactured and erected the structure, the erection being superintended by William Stuart. The steel was supplied by the Steel Company of Scotland and the Staffordshire Steel and Ingot Iron Co, the steel pins and rollers by S. Brown and Co, and the wrought iron by Handyside.
c.1905 photo here.
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The bridge was used by trams, despite the need to disconnect the overhead wires to swing the bridge. Trolley buses later replaced trams, as this 1966 photo shows. A 15 ton vehicle weight limit applied at that time.
At the time of demolition in 1975, a 10-ton weight limit applied to vehicles other than buses.
1975 photographs here.