What exactly is that smell?

[RobertInOntario]

The arcing inside the motor as the brushes rub against the commutator produces Ozone (Three oxygen atoms bonded together as opposed to normal atmospheric Oxygen molecules containing two atoms of Oxygen). Or, it could be old oil that you smell. Some lubricants have a sweet smell.

Thanks, Kevin -- I have heard people refer to an ozone smell. I have also noticed that the smell increases after lubricating the locos, but I haven't actually lubricated any of these for months, so maybe it's mainly the ozone smell I'm noticing. Cheers, Rob