Volume Six - Pre-Victorian to the Present Day - Select Aspects - Structural Analysis of the river Ely Subway by Rota Design Limited - 2015

However, the cyclical nature of the tidal waters of the river Ely would most probably have eventually caused a brittle failure of the cast iron since the forces induced into the structure have caused it to flex twice daily for a hundred years or so!

If we were required to predict this potential failure mode more accurately, it would be necessary to undertake laboratory experiments upon a representative selection of cast iron samples from the subway in order to establish the actual physical limitations of the cast iron and fixings bolts.

Now that the Cardiff Bay Barrage has taken away the twice daily variation in tide these cyclical events no longer occur and hence the life of the subway will be lengthened significantly.

The analysis we undertook upon the subway provides the opportunity to look back and marvel at the engineering brilliance of our Victorian engineering forefathers, who, without the aid of the computer, designed and built such amazing structures as the river Ely subway. Martin and I take our hats off to each and every one of them!

Since we completed this analysis, our young talented work experience engineer, Josh has completed his Masters Degree in Aeronautical Engineering at Bristol University and is employed designing high tech products. Well done Josh and many thanks for your input into our heritage project.

Cast Iron as a Construction Material

I felt it worth expanding upon the use of cast iron for the manufacture of the segments from which the subway is constructed. From 1830 until the turn of the 20th century, cast iron was used extensively for construction particularly for beams and columns used within buildings and bridges, etc. as well as for engine parts. The tunneling process had evolved as a construction kit by the use of segments cast by the British Hydraulic Company bolted together as they were in the case of this subway. The use of cast iron for columns continued into the 1930's and in my experience as an engineering fitter at Stirk Machine Tools here in Halifax back in the 1970's, was used extensively in the manufacture of machine tools since cast iron provides good compressive strength combined with vibration damping properties, ease of machining and complimented with natural lubrication.