| During 1948 & 1949 the Rock Island returned to ALCO and bought eight 3-unit freight locomotives (cab-booster-cab) to compare with the newer F7-model produced by GM-EMD. The latter began to arrive in 1949, with numbers commencing at 100A,B (cab, booster), and ending at 127A,B in 1951. Both the ALCO and GM-EMD units were powered by 1500-hp engines, and both rode on B-B trucks.This fleet of 42 multiple-unit locomotives replaced the older 4-8-4's in mainline service almost immediately, but the newer ones lasted until the fall of 1952, when they were retired long before they were worn out. |