Tay Bridge Disaster

The six o’clock train was only pulled by a small tank engine whereas the mail train was pulled by a very heavy 35 tonne loco. The extra load and the state of the bridge led to the collapse of one of the first five piers. However he and his team are unsure as to which one out of those five was the first to collapse. After this followed a number of pier failures not just the first one to collapse. If the piers had been in a reasonable state then it could have taken the failure of just one pier but in fact what happened was that all twelve of the high piers failed and collapsed one after other causing the rest of the bridge to eventually go with it.

According to the video the vibrations in the structure were ongoing and becoming more and more severe which could explain the collapsing of the piers. In this theory the disaster has in some ways been compared with the Tacoma Bridge Disaster which occurred in the USA which some people say was in no way related.

Another factor which is pretty important in this theory is the fact that the lugs were very poorly designed as they were made from cheap and brittle cast iron rather than the recommended option of a little more expensive but easy to shape and more bridge friendly wrought iron. This is probably due to the fact that the designer of the bridge – Sir Thomas Bouch – was famous for making cheap bridges which had not fallen down at the time of start of construction of the Tay Bridge and as many of his bridges were cheap ones, his money limit was probably very low which meant that he could not afford to use wrought iron and instead opted for the cheaper option of cast iron.

Another important factor is that Sir Thomas Bouch said that he had made no special allowance for wind pressure in his design.

The problem with the wind was that people couldn’t measure it exactly in those days. In fact according to Dr Lewis one of the outcomes of the Tay Bridge inquiry was that instruments like anemometers (used to measure wind speed) were developed.

Minor Theories

• The North British Railway, which owned the bridge, ran trains across it at more than the proper speed limit.
• Religious people in Dundee believed the disaster was God’s punishment because the railway ran trains on Sabbath Day (Sunday).
• The bridge had been badly made – holes in the girders had been filled with wax and iron fillings painted to look like solid iron. Fergus Ferguson, the man responsible ofr making the girders, had no real experience in engineering.
• The bridge had not been properly maintained – Henry Noble, in charge of this, was a brickwork expert but had no real knowledge of iron bridges.

Conclusion

I can reveal that the theory which appeals to me the most and for me is the most important and explains why the Tay Bridge collapsed is theory 2 – Tom Martin’s theory. This is because for me it has many reasons which explain why it collapsed such as the fact that the wind force put extra pressure on the bridge and also because I believe it answers all the main questions in the criteria for the mystery. This is however just my personal opinion and I respect the fact that others may think differently to me.