NAAIDT: NAAIDT Design & Technology Milestones: Ironbridge

Ironbridge
Abraham Derby
1777
Submitted by: Geoff Howard

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The Coalbrookdale Iron Bridge was the first structure of its kind in the world. By the late 18th century, East Shropshire was the most important iron producing area in Great Britain. The river Severn was used as the main method of transport but here was no way to cross the gorge at Coalbrookdale where Abraham Derby III had his ironworks. In 1773 Thomas Farnolls Pritchard suggested the idea of a bridge made of iron to John Wilkinson the ironmaster who joined with Abraham Derby and others to petition parliament for permission to build. Once the design was finalised, Derby undertook the building of the bridge starting in 1777 with the abutments, and in 1790 they were ready for the erection of the ironwork which was completed in November of that year. The cast iron parts were made by making a sand impression of wooden patterns and filling them with molten iron. Since an iron bridge had never been made before, craftsmen relied on the experience of other materials such as wood and the various pieces are designed to be dovetailed and tenoned together on assembly.