The increased weight of express trains in the United Kingdom during the first quarter of the twentieth century required larger, six-coupled locomotives, but new designs were being limited by the weight restrictions imposed on many underline bridges.
However, engineers were becoming increasingly aware of the significance of ‘hammer blow’ rather than ’deadweight’ in determining the safe loads for such bridges.
A committee of was established in 1923, funded jointly by the UK government and the railway companies, to carry out investigations in to the effects of hammer blow on bridges.
The committee under chairmanship of the physicist Sir James Alfred Ewing consisted primarily of railway civil engineers, but Sir Henry Fowler, Chief Mechanical Engineer of the London Midland and Scottish Railway was also later invited to join.
Among the results was a better understanding of hammer blow and the effects of oscillations in both locomotive springs and bridges.