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GWR Route: Banbury to Wolverhampton

Olton Station: gwro2692

Drawing showing strengthening to be carried out on Brunelís wrought iron bowed balloon-top bridge at Olton

Drawing showing strengthening to be carried out on Brunel's wrought iron bowed balloon-top bridge at Olton. The plan at the top of the drawing shows the skew required to cross the Turnpike Road. The use of the bowed balloon-top (tubular section) instead of a transverse flat flange was a characteristic of Brunel's bridges and although it increased the theoretical design strength and was more visually pleasing, it also increased the construction complexity (and consequently cost) and could suffer from undetectable internal corrosion (see 'gwro2694' for a photograph of a section through a typical wrought iron balloon-top). The main causes of replacement were however the gradual increase in locomotive axle weights and the requirement to widen bridges over roads. The bridge at Olton was eventually replaced with a lattice steel truss girder bridge when the Birmingham Main Line was quadrupled in the early 1930s. National Archives TNA (PRO) RAIL39/10/(14)

Robert Ferris

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