The 231 E series arose from the need to construct powerful steam locomotives for the increasingly heavy French express trains after the First World War. Instead of expensive new developments, André Chapelon was commissioned by the Paris-Orleans Railway to rework existing Pacific-type steam locomotives so that they met the new requirements. The engineer achieved the required increases in performance and savings in consumption mainly through improvements in thermodynamics. The success proved him right: the modified locomotive reached test speeds of up to 174 kilometres per hour, and in everyday operation it still made a proud 130 kilometres per hour top speed. With a 50 percent increase in performance and a simultaneous reduction in consumption costs, Chapelon turned the old steam locomotives into future-proof express locomotives.
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