Bull bridge accident
The Bull Bridge accident was a failure of a
The accident
The accident happened on the Midland Railway between Derby and Chesterfield, on the night of 26 September 1860. With visibility only about 10 yards (9.1 m) due to fog, the train was proceeding northwards at only 14 mph (23 km/h). It was a long train, with twenty-seven wagons loaded with salt, two loaded goods vans, and a brake van, hauled by a tender locomotive. The heavy load caused some slippage of the engine's driving wheels on the rail. Half a mile (800 m) beyond Ambergate station, the driver suddenly noticed that the engine's rear wheels were no longer on the rails. He shut off steam, stopped the engine and went to investigate. His tender was attached to only two wagons, and they were all off the rails too. There were two more wagons about 10 yards (9.1 m) behind, close to Bull bridge, a small viaduct over a local road. The next nine wagons behind were piled in a heap about 25 feet (7.6 m) high from the bottom of the road, reaching up to the telegraph wires by the side of the track. The guard in the brake van had been thrown headfirst against the front panel when the accident occurred but was not seriously hurt. All the wagons behind the bridge were still on the line.
Investigation
When examined by the driver and fireman, one of the cast-iron girders of the bridge was found to have fractured, unusually, near to one of the abutments rather than at the centre of the beam. The track was supported by a pair of identical girders with
The source of the defect remains unknown but may have been caused initially by a "cold shut," where the molten metal does not fuse during metal casting. It often occurs when two waves of fast cooling cast iron meet, but why it should have occurred only about 10 feet (3.0 m) from one end remains unknown. It could have grown with repeated loading from passing traffic, and Tyler thought it lucky that it had failed when a goods train passed, rather than a passenger train, when casualties would have been inevitable. So it is possible that fatigue had caused the failure by the steady growth of a brittle crack from the initial defect.
Implications
Together with the
References
Peter R Lewis, Disaster on the Dee: Robert Stephenson's Nemesis of 1847, Tempus (2007).