Perhaps this should be relocated to the DCC forum?
Perhaps...
Or perhaps the people who viewed your question simply do not know the answer. Sometimes it takes an expert on the specific subject couple of days to see the question (not everybody visits the forum several times a day like I do).
I'm not a B&O steam expert and I don't really know the terminology or the answer. From what I know, there are 2 types of articulated steam locos: Simple and compound.
Simple will produce 4 chuffs per wheel revolution if each engine. Due to wheel slip, then can go in and out of sync. Basically, those sound like 2 separate non-articulated locos.
Compound articulated locos feed the boiler steam to the high pressure cylinders of the 1st engine, then the lower pressure steam exhausting from those cylinders is then recycled to power the low-pressure cylinders of the 2nd engine. The bottom line is that in those engines you only have 4 chuffs per wheel revolution of the low-pressure engine. That is equivalent to a simple non-articulated 2-cylinder locomotive.
