Steam locomotive series 231 E of the French National Railways.The 231 E series arose from the necessity to design powerful steam locomotives for the increasingly difficult French express trains after the First World War. Instead of expensive new developments, André Chapelon was commissioned by the Paris-Orleans Railway to revise existing Pacific-type steam locomotives in such a way 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 was correct: The modified locomotive reached test speeds of up to 174 kilometers per hour, and in the day-to-day operation it still made a staggering 130 kilometers per hour. With an increase in performance of 50 percent and a simultaneous reduction in consumption costs, Chapelon made the old steam locomotives fit for the future.This text is machine translated.