Another reason why they sound so sharp may have been their design and construction. They were built in 1948 and 1949 with one piece cast steel frames with integral cylinders and rear cylinder heads. This produced a much more rigid design than a conventional built up frame with bolted on cylinders and certainly required less maintenance. Designed for branch lines with 45 pound rail, they developed 27,600 pounds TE at 75%. Using the US factor of 85% they would have been rated at 31,280 pounds TE.
Michael Allen