The latest issue of First & Fastest has a photo of a C&NW Pacific pulling 3 then-new gallery cars, not enough diesels yet being on the property. I always assumed that the gallery cars used HEP; did they actually have the axle-driven generators and batteries typical of that time, or did C&NW dummy up some kind of power car to fill the gap till the diesels arrived? (You can't tell from the photo whether there's anything behind the gallery cars--something is in the way.) I considered posting this on the C&NW forum but it seemed likely that more people who are up on Chicago commuter operations would see it here.
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The original St. Louis Car Co. order was built with steam heat and axle generators, possibly also diesel powered air conditioning like an "Enginator" self contained on each car. I think I read somewhere that all the cars had their own generator of some kind. There was no multiple unit hookups either, until the railroad came up with the cab car idea around the same time they switched to HEP. Trains were turned or the locomotives ran around like they did before the bilevels.