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over the River Irwell in Salford
No longer extant
1848 ' Springfield Lane Iron Bridge.
—Our readers are aware that for some months a project has been in agitation for erecting a new free bridge across the river Irwell, at Springfield Lane, and it is with much pleasure we can now state that the plans have been matured, and in the short space of four months another means of communication will be opened for the inhabitants of the opposite sides of the river. We yesterday inspected the plans, at the works of Messrs. Dunn and Elliott, of Windsor Bridge, Salford, who are the builders, and learnt the following particulars as to its construction.
The width of the river at the point selected is 94 ft. between bank and bank, and about the middle of the water passage, a series of stone pillars, supporting an entablature, and altogether forming a pier will be raised. The passage is to be formed of ten iron beams, each 45 1/2 feet long, five for one half the river, and five for the other. They will rest at one end upon side retaining walls of solid masonry, and on the other upon the centre pier, where they will be bound together so as to form five long beams stretching across the channel. Each beam will be equal to carry a weight of 50 tons in the middle, or about 800 for the whole. Above the girders will be laid wood beams, supporting two thicknesses of four inch plank, covered with asphalte an inch thick. The carriage way will be 24 feet wide, and the causeway on each side six feet each, with open palisading of elegant and light fret work. The surface of the bridge will be slightly curved, so as to throw off the wet, which the asphalte will keep from running down. We cannot enter into many into many interesting particulars which we have possession ; but shall reserve them to a future time. The structure and side walls will cost about £2,400, of which the Salford council contribute £1,000 we believe, and the rest made up by subscriptions. Mr. Carter has been appointed the collector, and as the subscribers are required to pay an instalment before the council will pay anything, it is desirable that the contributors should at once pay in their promised donations. Mr. Eaton Hodgkinson has had the plans submitted to him, and approved them.'
1848 'Interesting Test of Iron Girders for Spring Field Lane Bridge. —
Some very interesting experiments were made on Thursday afternoon, upon the ground intended to be laid out as the approach on the Manchester side of the Irwell to the new girder bridge now in course of erection at Springfield Lane, with the object of testing the strength of the girders intended to support the road-way of the passage. The experiments were of considerable interest to scientific men. and among those drawn to the place to witness them, were Professor Eaton Hodgkinson, F.R.S., Lieutenant Girton, from the Railway Department of the Board of Trade, we believe (a nephew of Mr. Strutt. of Derby), Mr. Richard Roberts, Mr. Fothergill, Mr. Davis, Mr. Bennett Woodcroft, Messrs. Dunn and Elliott, the contractors, and other gentlemen. Mr. W. Jenkinson, the Mayor of Salford, was also present, a party more particularly interested, the castings having been made by his firm. There were seven beams upon the ground, and of those, that which was considered to be the worst was selected to be tested. The mode of doing it was this: — Two beams were placed near together parallel, and at the extreme end, resting upon both, was a thick iron plate. Between them exactly in the middle of their length, resting upon the ground, a massive iron structure was fixed as a fulcrum, and the beam to be tested was then raised, placed upon the fulcrum and the supporting plate at the end, with the narrow flange lowest. That end was then strapped by two strong bolts, screwing together a plate secured on the top of the single beam, and another going beneath the two on which it rested. The other end was then quite free, and to it was applied a lever with a power of 8 for l, that is to say, if 1 cwt. was hung at the weight end the proportions of the lever gave a pressure at the fulcrum end of 8 cwt., and so on for any additional quantity. This power when applied to the beam, as the fulcrum on which it was poised was in the centre, by the laws of force, was doubled, a weight of 1 cwt. at the end of the lever was equal to a straining force of 16 at the centre of the beam. These arrangements made to the satisfaction of all present, the lever was loaded with pig metal of certain weights previously ascertained, and the results were as follow : [Table showing ‘pressure’ at centre in tons, from 30 to 54 tons, and deflection in inches]
'Load 30 tons, Deflection 1¼ inches
Load 38 tons, Deflection 1 5/8 inches
Load 42 tons, Deflection 2 1/8 inches
Load 46 tons, Deflection 2 3/8 inches
Load 50 tons, Deflection 2¾ inches
Load 54 tons, Deflection 3 inches
'The test was carried no further, for at 58 tons the beam broke or tore through in the centre, in an irregular course but rather inclined to the diagonal, before the deflection could be taken. The result was exceedingly satisfactory to all, including Professor Hodgkinson, whose opinion in these matters is of the highest value. The contractors, Messrs. Dunn and Elliott, had guaranteed that each girder should be able to sustain a pressure of 50 tons; the experiment had proved that the one considered to be the worst was capable of resisting a straining force of between 54 and 58 tons—a weight at least ten times more, it is likely, than will ever be carried across any one girder. It is not expected that more than five tons will be taken over at once, and the Probability is the weight in that case will be on more one girder - The length of each beam is 49 feet (half the distance across the river), and the weight of each 7½ tons. There will be 10 beams, 5 for one half the river and five for the other, and each will be of the strength equal to that so fairly tested with the results above stated.'
Note: 'Lieutenant Girton' referred to above was almost certainly Douglas Strutt Galton.
The cast iron bridge was completed in 1850, but was replaced in 1880. The new bridge was designed by Arthur Jacob, the Salford Corporation Engineer, and the main contractor was Abram Pilling and Son. The riveted wrought plate girders were made less drab in appearance by superimposing cast iron ornamentation.
The bridge would have been scrapped when the River Irwell was straightened.