Big Bertha's cylinder arrangement was unusual.
The configuration is expressed in the engine's model numbers as the letter "O", standing for "opposed" in reference to the cylinder arrangement.
In terms of the cylinder arrangement, Drummond's first foray into 4-6-0 locomotive design was highly unusual.
The desire to improve the diesel engine's power-to-weight ratio produced several novel cylinder arrangements to extract more power from a given capacity.
The accompanying plot shows the proportional operating region for a co-axial cylinder arrangement.
The cylinder arrangement of the compression engine was horizontal.
After withdrawal, the "Duke" was initially selected for the National Collection, though it was later decided that only the cylinder arrangement was of interest.
Common cylinder arrangements are from 1 to 6 cylinders in-line or from 2 to 16 cylinders in V-formation.
That said, the engine did not perform especially well, so that the two units were converted into locomotives with a conventional cylinder arrangement.
They shared similar cylinder arrangement (two outside), internal boiler design and size and 6 foot driving wheel diameters.