Fairbairn steam crane

. This photograph also shows the distinctive double rows of rivets that make up 'chain riveting.' The crane's innovation was in the use of a curved jib, made of riveted wrought iron platework to form a square-section box girder. This curved jib could reach further into the hold of a ship, clear of the deep gunwales alongside the quay. Designing a strong curved jib required Fairbairn's advanced theoretical understanding of the mechanics of a box girder. The tension forces were carried by the outer, convex surface of the girder which was made of back plates being chain-riveted together. The inner surface carried a compressive load. To avoid plate crumpling, it was made as a cellular structure: an inner plate and webs formed three rectangular cells, effectively box girders in their own right. The character of a box girder is to resist torsional twisting, so a composite face built up of them is also good at resisting crumpling. They were particularly favoured in naval dockyards for fitting battleship guns; Hong Kong had a battery of four. == Bristol ==

The only surviving Fairbairn steam crane is in Bristol, on the quayside at Wapping Wharf in the Floating Harbour. It is in the care of the M Shed museum, located on the adjacent Prince's Wharf. Construction In the 1870s, Bristol Docks was going through a period of expansion and modernisation in the face of increasing competition from other ports. Iron-hulled ships were becoming larger, cargoes heavier, and there had already been investment in building a railway line along the harbour quay. Crane capacity was limited, though – none of the harbour's 17 cranes being able to lift more than 3 tons. Accordingly, a more powerful steam crane was ordered, to be capable of lifting 35 tons and loading it directly onto a railway wagon. This was ordered from local makers Stothert & Pitt in 1875, although to the Fairbairn pattern. As for the later Fairbairn cranes, the original cell plate was changed to a design of a single flat plate stiffened by riveted T section ribs, rather than the original cellular structure. In service Although mechanically capable, the crane was not a great success commercially. In 1890 it was only used for 16 days of the year, for a profit of just 11s. 6d. as the last surviving Fairbairn steam crane. From 1988, it was restored to operational condition as part of the Bristol Industrial Museum. The crane operates on special museum days, such as bank holidays and the Harbour Festival. == Seville ==

A hand-cranked example survives in Seville, Spain. == Dover ==

Another Fairbairn crane survives at Dover, on the quayside of Wellington Dock. It is now a scheduled monument. This is a hand-cranked crane of 1868, built by the Fairbairn Engineering Company of Manchester. When originally installed it was rated at 50 tons and worked by four men. The Ordnance Department of the Royal Navy used it for handling cannon. In later years it was down-rated to 20 tons and was used for lifting yachts from what was now Dover Marina. In 2014 the crane was 'lovingly restored' and repainted, with an obtrusive vertical steel prop beneath the jib. == References ==