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Testing the Railway Bridges and Viaducts.

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With the poor state of repair of the railway viaduct in Manilla threatening to end Manilla Shows being held there [ The Northern Daily Leader, Sunday, March 4 2018, The Northern Daily Leader, Tuesday, March 6 2018], here’s the original newspaper article describing how the viaduct in Tamworth was tested on November 16, 1881 …


The Armidale Express and New England General Advertiser, Friday, December 2, 1881

Testing the Railway Bridges and Viaducts.

(From The News.)

On Wednesday, the 16th instant, an important step was taken towards the final acceptance by the Government of the contract for the Railway from Tamworth to Uralla. We refer to the testing of the long timber viaduct that crosses the valley of the Peel in Tamworth, and the two iron bridges which span the Peel River and adjoining Manilla Road. The Inspecting Engineer arrived from Sydney with the testing apparatus on Tuesday week last, when the final arrangements were made for the morrow’s work.

A few words will describe the instruments used. They consist of small round clock-like machines, about 8 inches in diameter, on the face of which are graduations representing inches and decimal parts of inches. The arm or index is short piece of steel, very like the large hand of an ordinary clock, to the end of which is attached a coil of spiral watch spring, a piece of cat-gut being used to the end of the spring. A chain consisting of links of fine wire, a few nails, and some short battens, are all besides the discs needed for the testing.

The testing was conducted as follows, the two iron bridges being first tried, the wooden viaduct afterwards :— A batten was driven into the ground under the centre of each bridge, and the wire chain having been fixed to it by a tack, the latter was passed up to the bridge, a hole for it having been bored in the planking; the end of the chain on the bridge was fixed in rigid tension to the end of the cat-gut in one of the discs, which was itself firmly fastened to the bridge by a thumb-screw.

The testing weight was composed of three locomotive engines coupled together —two Government and one (the “Murrumbidgee”) belonging to Messrs. A. and R. Amos contractors. Their total dead weight may be taken at 174 tons 8 cwt. At first they were brought slowly over the bridges and allowed to rest when the middle engine was about on the centre of the bridge, this was done once or twice, with the result that the deflection was found to be in the Peel River Bridge about 80 of an inch, and in the Street Bridge about 25 of an inch. The locomotives were then sent up the incline on the bank at the North end of the viaduct and were brought down at full speed, and the deflection was found to be about 85 in the large and 30 of an inch in the small bridge, and there was no permanent set at all observable. This was considered a good result, and the two Government engines were sent away ; the wooden viaduct being loaded with the “Murrumbidgee” only, which weights 56 tons or thereabouts.

The only attraction in the method adopted in testing the viaduct was that the discs instead of being fixed to the top were secured to battens placed in the ground under each bay, and the chains were nailed to the wooden beams in the centre of the bridge. The deflection was very slight in each case, the greatest being .55 and the least about .30 of an inch. The spans of the wooden viaduct are chiefly 29 feet 6 inches, although there are two bays of 30 feet and five of 25 feet in it. The length of the large iron girders over the Peel River is 160 feet, and over the streets 60 feet. The testing was conducted by Mr. Wade, Inspecting Engineer, Mr. J. G. Griffin, District Engineer, and Mr. T. Parkinson, Inspector of Works on the part of the Government, and by Mr. John Owen, Manager, and Mr. J. S. Bennett, Engineer on the part of Messrs. A. & R. Amos, the contractors.

Written by macalba

March 6, 2018 at 3:34 pm

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