ironbrdge4

Photographs for the BBC Timewatch progamme
'The Mystery of the Ironbridge'
The Ironbridge at Telford was designed by Abraham Darby
Extracted from the Ironbridge Gorge Museum exhibit details
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Photos Ribs	Uprights	18thC Defects	Photos on site	Slide show CD	Home


Half Scale Model of the Iron Bridge


This is a half scale model showing the early stages, which is an experiment to help us learn more about how the full size Iron Bridge may have been put up. The first 3 ribs have been erected,but the full size bridge has 5 ribs linked by many more castings	The timber scaffold and the iron castings you see are based on a painting of 1779. The iron pieces were cast in open sand moulds, just like the original bridge. The Timber works as a crane with several lifting points to raise the iron from a barge on the water below	The model was made for a BBC2 'Timewatch' programme in October 2001 to be shown in early 2002. Soldiers from the Royal Engineers (51 Field Squadron) erected the scaffold and the ironwork using 18th Century methods. It proved that this arrangement was possible.

Technical Details


Ironwork The original ribs were cast in 2 pieces joining at the centre,each half weighing 5.75 tons. At half scale, they weigh only 15 cwt (680Kg). The span of 1 arc is 50feet (15.24m) and the chord length of each rib was 37 feet (11.3m). In the uprights holes would allow other parts of the bridge to be slotted in place.
Scaffold The timber poles used for erection are 33 feet (10m) high, though the original scaffold poles would have stood in the river Severn and must have been nearly 70 feet (21.3m). They acted as derricks (cranes) and the frame may have been moved to a new position for each rib.
Ropes Only hemp ropes were used to build the model,hauled by teams of soldiers. Some ropes have since been replaced by steel cables for safety. A trial lift of a 5 ton weight using the scaffold, hemp ropes and pulleys required 25 people to raise it from the ground.
Abutments The original abutments are in stone, not brick as shown here, they provide support for the base plates. Only the middle 3 base plates out of a set of 5 have been used, these are only 1" (25mm) thick, unlike the originals which were 4" (100mm).

Project Team


BBC Wales Deborah Perkin Producer	Historic Adviser David de Haan Ironbridge Gorge Museum	Project Engineer Jamie Hillier Buro Happold
Erection Team Royal Engineers, 51 Squadron (Air Assist) Led by Lt. Ben Day	Iron Castings Nigel Downs H. Downs & Sons Ltd Huddersfield	Technical Drawings Ironwork Bill Blake English Heritage Metric Survey Team
Structural evaluation Andrew Smith	Site Management Alex Medhurst Ironbridge Gorge Museum	Abutments/site support Staff of Blists Hill Victorian village

Links
Click on the links below to see more


Production of ribs
Production of uprights
18th C Casting defects
Site photographs
Home H. Downs
CD Available
Crown Joint Details