Mills Hill Bridge, Chadderton

Railway bridge over Rochdale canal cc-by-sa/2.0 - © Michael Smith - geograph.org.uk/p/6814873

Section of part of Chalk Farm railway bridge, which was of similar construction to Mills Hill bridge

in Chadderton, near Oldham

Also known as Bridge 69B, and locally as Th' Iron Dongle. The name Mills Hill Bridge is assigned to it in 'Britain's Historic Railway Buildings' by Gordon Biddle.

The attractive and historically important skewed iron bridge carried the Manchester and Leeds Railway between Manchester and Rochdale over the Rochdale Canal, adjacent to Lock 61 (Scowcroft).

Whoever was responsible for saving this bridge from demolition has done a great service to the memory of the designers, foundry pattern makers and moulders, fitters, erectors and stonemasons responsible for its construction.

A girder bridge was added immediately alongside in the late 19thC to provide quadruple tracks. In the 1970s the line reverted to double tracks and the original bridge was taken out of use and had its deck removed.

Grade II listed (No. 1356431). Historic England listing here. For some reason, this gives the construction date as 1863. However, the line had been built over the Rochdale canal by 1839, and the design is consistent that of several similar bridges on railways built by George Stephenson and Robert Stephenson in the late 1830s (see below). In fact the bridge was mentioned in September 1838, in an article about a trial run on part of the line: 'The Rochdale canal is next crossed, for the first time, about a quarter of a mile further, by a cast-iron trussed-beam bridge, with an arch of 75 feet span; the rails being about 20 feet above the surface of the water.'. Further:-

1839 'From Mills hill the train started, after a halt of four minutes, at seventeen minutes before one o'clock. The line here crosses the valley of the Irk on an embankment of nearly sixty feet in height. The eye of the passenger is delighted in the progress by very interesting views of a well-cultivated and varied country; but it is soon attracted by a large iron bridge, by which the train crosses the Rochdale canal; it is a skew of 73 1/2 feet span, and was built by Messrs. Radfords and Co, to whose workmanship it does the highest credit.'

It is rare example of an iron bowstring (tied arch) railway bridge with a suspended deck, and is almost certainly the earliest surviving example of this type. Each side of the bridge comprises a pair of cast iron girders, spaced several feet apart. These are joined to each other by transverse X-braces, bolted to the vertical ribs of the girders. Each of these cast iron girders embodies a 'Tudor' arch as its principal member, and the 'string' of this 'bow' is a pair of tensioned rods for each girder. Each of these tensioned wrought iron rods comprises several bars joined by cast iron spools with tapered cotters. Driving in the tapered cotters would provide a degree of pre-tensioning. Decorative castings are attached to the top and bottom of the girders.

The transverse X-braces have a vertical central hole through which a wrought iron rod passes. From these rods are suspended fish-bellied cross beams which supported the deck. See Chalk Farm Bridge drawing.

Details of construction of a somewhat similar bridge can be seen in drawings of Stephenson's 1837 bridge which carried the London & Birmingham Railway over Regent's Canal near Chalk Farm.

At some point the deck supports were augmented by the insertion of additional cross beams between the original cast iron beams. These additional beams are of riveted wrought iron or steel construction. The ends of these horizontal beams turn upwards between the pairs of girders, and terminate in riveted crossheads which sit on top of the girders to take the weight.

Numerous photos, showing details, here.

Geograph entry here. The photo is reproduced above. This was taken in 2021 and shows that the decorative castings below the girder to be missing from the right hand side, presumably removed for repair.

Note: The larger Todmorden - Gauxholme No. 2 Viaduct is of similar construction, but has been much altered. This had a twin - part of Whiteleys Viaduct - but the bowstring girders were replaced in 1939 by steel plate girders.

See Also

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