Bristol & Exeter Pearson 9 feet 4-2-4T

The broad gauge Bristol & Exeter Railway took over the “Flying Dutchman”, which started from London-Paddington, on the last section between Bristol and Exeter. To accommodate this fastest train in the world, eight tank locomotives with a driving wheel diameter of nine feet or 2,743 mm were ordered from Rothwell & Co. These were the largest wheels ever found on a commercially used locomotive.

There was a bogie at each end of the locomotives, while the driving wheels had no flanges. The load on the bogies was lower than that on the driving axle. Another feature was the outside frame, which ran from front to back and in which the driving axle was also mounted. They often reached speeds of around 80 mph (129 km/h), with the highest recorded speed on a slight decent reaching 81.8 mph. 

After a derailment in 1876, the remaining seven locomotives were rebuilt. They received driving wheels with a diameter of only eight feet and ten inches, which now had flanges. In addition, the outside frame was eliminated and there was now a longer overall wheelbase. Furthermore, the cylinders were now larger and, the larger boiler above all had a larger grate because it now burned coal instead of coke. Three were even converted into tender locomotives with a 4-2-2 wheel arrangement.