Around 1876 the decision was made to double the number of lines on the GWR starting at the London end. Herapath’s Railway Journal reported that the two new tracks added to the north of the existing railway would be used for ‘auxiliary or slow goods lines ...’ Fast passenger trains would continue to use the original lines. At Hanwell this involved widening the embankments, the Wharncliffe Viaduct, and the skew bridge. Work on the Wharncliffe Viaduct was extensive but relatively straightforward. The Uxbridge Road crossing presented a major difficulty. Brunel had been in his grave for more than fifteen years, but the legacy of his problematic bridge continued to haunt the Great Western Railway Company. The issue was that the support columns and girders on the north-west side of the original bridge (the Southall side), as well as the flamboyant ‘proscenium arch’ and its folly, were strung out immediately under where the new lines would be positioned. Any new span would have to be built over the top without interfering with the function of the earlier (1847) structure. A further complication arose from the fact that the layout of the crossroads had to be preserved. The new bridge, being parallel to the existing one, would have to be located a significant distance north-west of the point where the two roads crossed. Either a very long span or two separate bridges, one over each road, would be needed. No contemporary documentation regarding the bridge can be found. As with Brunel’s box girder bridge, most of what is known is from the 1906 article in the GWR magazine written some thirty years after the event. It says: In 1876-77 the northern [north-westerly] wing of the original bridge was demolished to admit of a widening for additional lines, the structure being formed of wrought iron lattice girders, cross girders and an iron plate floor. The decision was made to build two spans utilizing one of the existing cast iron pillars and a new brick ‘island’ structure for the central support, and extended brick abutments to the widened embankments at either end. A lattice girder bridge design in wrought iron was chosen for the main span crossing the Uxbridge road. William Fairbairn’s experiments had shown that the box girder was the most efficient use of material in achieving the maximum load bearing capacity for a given amount of wrought iron used. The lattice girder ‘through truss’ retained most of the benefits of a box girder while being more versatile, more economical of material, easier to fabricate, and much easier to maintain corrosion free. The truss consisted of two substantial I-beams connected between their bottom flanges with transverse girders to form the bridge deck; their webs were not solid as in conventional I-beams, but double layer wrought iron trellises. This design was very popular at the time and many examples can be seen on the British railway system, including the bridge carrying the railway across the River Thames at Kew. The second, much shorter span bridged Windmill Lane, and consisted of a pair of conventional I-beams with solid webs. It is evident that the deck plan of any skew bridge built with economy is a parallelogram rather than a rectangle. In order that the main girders are no longer than they need to be, they are offset with respect to each other along the longitudinal axis of the bridge. The deck plan of each span of the new bridge was a trapezium, and in each case the two girders were longitudinally offset—but in different directions—and in both cases one girder was longer than the other. It is difficult to visualise the layout without pictorial assistance but a full plan showing both Brunel’s bridge with all of its columns and girders and the two new structures would be more confusing than helpful. There is a large-scale map in the National Archives dating from 1913 which shows just the road layout and the outline of the bridges, and this has been annotated to show the position of the two new bridges. In order to accommodate the new span, it was necessary to demolish the proscenium arch and folly on the west side of Brunel’s bridge, and remove any embellishments on top of the girders there. The clearance between the bottom of the new bridge and the tops of the box girder array on the existing bridge was chosen to be around fifteen inches; a box shaped spacer of this depth was fixed to the top of the existing box girder immediately over the cast iron column at the north-west corner of the crossroads. This also supported one side of the short bridge crossing Windmill Lane. It is presumed that main line trains continued to use the original bridge during these works, and that a timber support structure was built over the two roads to allow unrestricted road traffic to continue while the new bridges were built. The photograph, which was taken last year, shows about the best view possible of the trellis bridge given that it is sandwiched between the two later steel structures. The picture also affords a nice view of the shorter span built to cross Windmill Lane. The unsightly blue boarding on the right blocks in an old builder’s yard which was built on the original position of Windmill Lane before it was diverted sometime after 1913 to its present position. The bridge deck is continuous from the trellis bridge, over the brick island, and the short bridge over Windmill Lane The new spans were finished by some time in 1877 and the trellis bridge would have completely changed the appearance of the Hanwell bridge to anyone coming along the Uxbridge Road from Southall, likewise to a traveller along Windmill Lane from Greenford. From the Hanwell side, the bridge was unaltered, the new span being entirely hidden from view by Brunel’s theatrical arch and its accoutrements which remained on that side of the bridge. So it is most curious that nothing about this substantial change in a local landmark can be found in any of the local newspapers of the period. Likewise no photographs are to be found in the public domain.
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AuthorWelcome to the Mirli Books blog written by Peter Maggs Archives
March 2024
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