 Although of similar size to the X class 2-8-2 goods locomotive, the R's more modern design features such as larger volume smokebox and better valve events courtesy of larger diameter piston valves with long travel contributed to its significantly higher horsepower output than the 1,400 drawbar horsepower () output of the X class.Features such as the mechanical stoker, smooth riding characteristics and large, comfortable cab also made them popular with crews.The R's impressive debut was cut short by the introduction of the B class diesel electric locomotives from July 1952.