John Speller's Web Pages Pearson's 4-2-4 Tanks (B&ER)

John Speller's Web Pages - GWR Broad Gauge - B&ER

Pearson's 4-2-4 Tanks

Designed by the B&ER's Locomotive Superintendent, James Pearson (1820-1891), the 4-2-4 tanks were perhaps the culmination of the Brunel philosophy of low piston speeds and light axle loadings. Rather than being attached to the frames, weight was saved by suspending the driving wheels directly from the boiler. This was done using a revolutionary vulcanized rubber suspension supplied by the Moulton company of Bradford-on-Avon. Vulcanized rubber springs had already been used by Sir Daniel Gooch on his "Bogie" Class 4-4-0 saddle tanks two years previously. The 9 ft. driving wheels gave a very low piston speed. The design seems to have been based in part upon the "Carroll of Carollton," a 4-2-4 with 7' 0" driving wheels built for the Boston & Worcester Railroad by Ross Winans in 1849. C. E. Stretton described the locomotives thus: "The author remembers that at a speed of about 60 miles an hour the engine was remarkable for its very easy riding ... Mr. Pearson many years ago informed the writer that his engines had been officially tested at 81 miles an hour, and that the average consumption of coke over a distance of 100,000 miles was only 21 lbs per mile. This maximum speed of 81 miles an hour was attained thirty-nine years ago [1857], but it still remains the highest on record." In practice the low adhesion weight rendered the Pearson tanks unsuitable for express passenger work, especially climbing Wellington Bank, and they were mostly used on branch lines, including the Yeovil and Tiverton branches.

James Pearson originally worked on the London & Croydon Railway and because of his experience with the Atmospheric Railway was brought in by Brunel to be Atmospheric Superintendent of the South Devon Railway. From 1850 to 1876 he was Locomotive Superintendent of the Bristol & Exeter Railway.

Having 9 ft. driving wheels was not, of course, a record. Some of the earliest locomotives on the Great Western Railway had 10 ft. driving wheels, and (probably in response to the B&ER) the Chemins de Fer de l'Ouest in France built a 2-4-0 locomotive, "L' Aigle," exhibited at the Paris Exhibition of 1855, with 9' 4" driving wheels.
The first photograph shows one of James Pearson's amazing 9 ft. 4-2-4 well tanks in its original condition. No. 42 was built by Rothwell & Co. of Bolton in 1854.
Bogie design of Pearson's 4-2-4 well tanks
B&ER 4-2-4 well tank No. 44, its massive 9 ft. wheels dwarfing the crew
B&ER No. 46 shown in original condition at Bristol in about 1870
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