Articulated engines seemed tailor-made for SP's tough route over the Sierra-Nevadas. But the 2-8-8-2s that arrived in 1909 made too much smoke in tunnels and snowsheds. As a quick fix, crews began running tender-first. This inspired a new design with the cab ahead of the boiler that came to be known as a "cab forward." As traffic levels grew, the road introduced a new generation of 4-8-8-2 cab forwards, class AC-4, in 1928. These were followed a year later by 16 almost identical but slightly heavier AC-5s. For the next 25 years, these engines (and several later classes) lifted tonnage and passengers over most of SP's western lines.
 
These superb replicas feature the correct flat-faced cab, plus authentic whistle and bell sounds. Models can be run on code 70, 83 or 100 rail; a minimum radius of 22" is recommended.