Reply to "The question of B units (from AB, ABA, or ABBA sets) in O gauge trains and why they DON'T SMOKE... Did the prototypes not smoke too? Or is this a cost saving / amp draw UL approval issue?"

Lionel has come a long way with improvements on their smoke units.

The Legacy engines I have (all recent - last 5 years) smoke very well, no complaints.

My earlier Legacy 10 wheeler also smoked very well and no complaints there either.

I've moved away from most but not all TMCC which would include K Line as they also had TMCC.

As well, K Line used tethers to facilitate smoke units in the B Units and a slave in the A.

Just a preference..........the Legacy sounds won me over especially with the vastly improved smoke units.  They almost match MTH but not quite.

I do like a number of MTH engines and I have several....just not a fan of tethered units or the new drawbar arrangement on MTH steamers although I tolerated them.