In 1928, Alco built five D-1a 4-6-6T bi-directional steam locomotives (road numbers 400 to 404) for the Boston & Albany Railroad to use in commuter service around Boston. In my opinion, they are the most interesting of all steam locomotives. These engines ran in a circuit – outbound on the main line to Riverside, inbound on the Highland Branch back to South Station, and also in the opposite direction. Since they were double-ended, it was unnecessary to turn them before the next run.
The first O gauge model, with road number 403, was made by K-Line in 2005. The tooling was later acquired by Lionel, and a Legacy version with road number 400 was produced in 2020.
The tank engines had 63-inch drivers, ran at 215 psi boiler pressure, weighed 352,000 pounds, and developed 41,600 pounds tractive effort. They were the largest tank engines ever to run in the United States and were designed for rapid acceleration. Their tractive effort was almost equal to that of a Boston & Albany 4-6-2 Pacific. They were retired in 1951.
Video shows #400 and #403 running on my 12’-by-8’ layout.
Whenever Lionel makes a B&A tank engine model with any of the three remaining road numbers, I will be a buyer.
MELGAR